| Message ID | 20190617180109.34950-2-sdf@google.com |
|---|---|
| State | Changes Requested |
| Delegated to: | BPF Maintainers |
| Headers | show |
| Series | bpf: getsockopt and setsockopt hooks | expand |
On Mon, Jun 17, 2019 at 11:01:01AM -0700, Stanislav Fomichev wrote: > Implement new BPF_PROG_TYPE_CGROUP_SOCKOPT program type and > BPF_CGROUP_{G,S}ETSOCKOPT cgroup hooks. > > BPF_CGROUP_SETSOCKOPT get a read-only view of the setsockopt arguments. > BPF_CGROUP_GETSOCKOPT can modify the supplied buffer. > Both of them reuse existing PTR_TO_PACKET{,_END} infrastructure. > > The buffer memory is pre-allocated (because I don't think there is > a precedent for working with __user memory from bpf). This might be > slow to do for each {s,g}etsockopt call, that's why I've added > __cgroup_bpf_prog_array_is_empty that exits early if there is nothing > attached to a cgroup. Note, however, that there is a race between > __cgroup_bpf_prog_array_is_empty and BPF_PROG_RUN_ARRAY where cgroup > program layout might have changed; this should not be a problem > because in general there is a race between multiple calls to > {s,g}etsocktop and user adding/removing bpf progs from a cgroup. > > The return code of the BPF program is handled as follows: > * 0: EPERM > * 1: success, execute kernel {s,g}etsockopt path after BPF prog exits > * 2: success, do _not_ execute kernel {s,g}etsockopt path after BPF > prog exits > > Note that if 0 or 2 is returned from BPF program, no further BPF program > in the cgroup hierarchy is executed. This is in contrast with any existing > per-cgroup BPF attach_type. This is drastically different from all other cgroup-bpf progs. I think all programs should be executed regardless of return code. It seems to me that 1 vs 2 difference can be expressed via bpf program logic instead of return code. How about we do what all other cgroup-bpf progs do: "any no is no. all yes is yes" Meaning any ret=0 - EPERM back to user. If all are ret=1 - kernel handles get/set. I think the desire to differentiate 1 vs 2 came from ordering issue on getsockopt. How about for setsockopt all progs run first and then kernel. For getsockopt kernel runs first and then all progs. Then progs will have an ability to overwrite anything the kernel returns.
On 06/18, Alexei Starovoitov wrote: > On Mon, Jun 17, 2019 at 11:01:01AM -0700, Stanislav Fomichev wrote: > > Implement new BPF_PROG_TYPE_CGROUP_SOCKOPT program type and > > BPF_CGROUP_{G,S}ETSOCKOPT cgroup hooks. > > > > BPF_CGROUP_SETSOCKOPT get a read-only view of the setsockopt arguments. > > BPF_CGROUP_GETSOCKOPT can modify the supplied buffer. > > Both of them reuse existing PTR_TO_PACKET{,_END} infrastructure. > > > > The buffer memory is pre-allocated (because I don't think there is > > a precedent for working with __user memory from bpf). This might be > > slow to do for each {s,g}etsockopt call, that's why I've added > > __cgroup_bpf_prog_array_is_empty that exits early if there is nothing > > attached to a cgroup. Note, however, that there is a race between > > __cgroup_bpf_prog_array_is_empty and BPF_PROG_RUN_ARRAY where cgroup > > program layout might have changed; this should not be a problem > > because in general there is a race between multiple calls to > > {s,g}etsocktop and user adding/removing bpf progs from a cgroup. > > > > The return code of the BPF program is handled as follows: > > * 0: EPERM > > * 1: success, execute kernel {s,g}etsockopt path after BPF prog exits > > * 2: success, do _not_ execute kernel {s,g}etsockopt path after BPF > > prog exits > > > > Note that if 0 or 2 is returned from BPF program, no further BPF program > > in the cgroup hierarchy is executed. This is in contrast with any existing > > per-cgroup BPF attach_type. > > This is drastically different from all other cgroup-bpf progs. > I think all programs should be executed regardless of return code. > It seems to me that 1 vs 2 difference can be expressed via bpf program logic > instead of return code. > > How about we do what all other cgroup-bpf progs do: > "any no is no. all yes is yes" > Meaning any ret=0 - EPERM back to user. > If all are ret=1 - kernel handles get/set. > > I think the desire to differentiate 1 vs 2 came from ordering issue > on getsockopt. > How about for setsockopt all progs run first and then kernel. > For getsockopt kernel runs first and then all progs. > Then progs will have an ability to overwrite anything the kernel returns. Good idea, makes sense. For getsockopt we'd also need to pass the return value of the kernel getsockopt to let bpf programs override it, but seems doable. Let me play with it a bit; I'll send another version if nothing major comes up. Thanks for another round of review!
On 06/18, Stanislav Fomichev wrote: > On 06/18, Alexei Starovoitov wrote: > > On Mon, Jun 17, 2019 at 11:01:01AM -0700, Stanislav Fomichev wrote: > > > Implement new BPF_PROG_TYPE_CGROUP_SOCKOPT program type and > > > BPF_CGROUP_{G,S}ETSOCKOPT cgroup hooks. > > > > > > BPF_CGROUP_SETSOCKOPT get a read-only view of the setsockopt arguments. > > > BPF_CGROUP_GETSOCKOPT can modify the supplied buffer. > > > Both of them reuse existing PTR_TO_PACKET{,_END} infrastructure. > > > > > > The buffer memory is pre-allocated (because I don't think there is > > > a precedent for working with __user memory from bpf). This might be > > > slow to do for each {s,g}etsockopt call, that's why I've added > > > __cgroup_bpf_prog_array_is_empty that exits early if there is nothing > > > attached to a cgroup. Note, however, that there is a race between > > > __cgroup_bpf_prog_array_is_empty and BPF_PROG_RUN_ARRAY where cgroup > > > program layout might have changed; this should not be a problem > > > because in general there is a race between multiple calls to > > > {s,g}etsocktop and user adding/removing bpf progs from a cgroup. > > > > > > The return code of the BPF program is handled as follows: > > > * 0: EPERM > > > * 1: success, execute kernel {s,g}etsockopt path after BPF prog exits > > > * 2: success, do _not_ execute kernel {s,g}etsockopt path after BPF > > > prog exits > > > > > > Note that if 0 or 2 is returned from BPF program, no further BPF program > > > in the cgroup hierarchy is executed. This is in contrast with any existing > > > per-cgroup BPF attach_type. > > > > This is drastically different from all other cgroup-bpf progs. > > I think all programs should be executed regardless of return code. > > It seems to me that 1 vs 2 difference can be expressed via bpf program logic > > instead of return code. > > > > How about we do what all other cgroup-bpf progs do: > > "any no is no. all yes is yes" > > Meaning any ret=0 - EPERM back to user. > > If all are ret=1 - kernel handles get/set. > > > > I think the desire to differentiate 1 vs 2 came from ordering issue > > on getsockopt. > > How about for setsockopt all progs run first and then kernel. > > For getsockopt kernel runs first and then all progs. > > Then progs will have an ability to overwrite anything the kernel returns. > Good idea, makes sense. For getsockopt we'd also need to pass the return > value of the kernel getsockopt to let bpf programs override it, but seems > doable. Let me play with it a bit; I'll send another version if nothing > major comes up. > > Thanks for another round of review! One clarification: we'd still probably need to have 3 return codes for setsockopt: * any 0 - EPERM * all 1 - continue with the kernel path (i.e. apply this sockopt as is) * any 2 - return after all BPF hooks are executed (bypass kernel) (any 0 trumps any 2 -> EPERM) The context is readonly for setsockopt, so it shouldn't be an issue. Let me know if you have better idea how to handle that.
On Tue, Jun 18, 2019 at 11:09 AM Stanislav Fomichev <sdf@fomichev.me> wrote: > > On 06/18, Stanislav Fomichev wrote: > > On 06/18, Alexei Starovoitov wrote: > > > On Mon, Jun 17, 2019 at 11:01:01AM -0700, Stanislav Fomichev wrote: > > > > Implement new BPF_PROG_TYPE_CGROUP_SOCKOPT program type and > > > > BPF_CGROUP_{G,S}ETSOCKOPT cgroup hooks. > > > > > > > > BPF_CGROUP_SETSOCKOPT get a read-only view of the setsockopt arguments. > > > > BPF_CGROUP_GETSOCKOPT can modify the supplied buffer. > > > > Both of them reuse existing PTR_TO_PACKET{,_END} infrastructure. > > > > > > > > The buffer memory is pre-allocated (because I don't think there is > > > > a precedent for working with __user memory from bpf). This might be > > > > slow to do for each {s,g}etsockopt call, that's why I've added > > > > __cgroup_bpf_prog_array_is_empty that exits early if there is nothing > > > > attached to a cgroup. Note, however, that there is a race between > > > > __cgroup_bpf_prog_array_is_empty and BPF_PROG_RUN_ARRAY where cgroup > > > > program layout might have changed; this should not be a problem > > > > because in general there is a race between multiple calls to > > > > {s,g}etsocktop and user adding/removing bpf progs from a cgroup. > > > > > > > > The return code of the BPF program is handled as follows: > > > > * 0: EPERM > > > > * 1: success, execute kernel {s,g}etsockopt path after BPF prog exits > > > > * 2: success, do _not_ execute kernel {s,g}etsockopt path after BPF > > > > prog exits > > > > > > > > Note that if 0 or 2 is returned from BPF program, no further BPF program > > > > in the cgroup hierarchy is executed. This is in contrast with any existing > > > > per-cgroup BPF attach_type. > > > > > > This is drastically different from all other cgroup-bpf progs. > > > I think all programs should be executed regardless of return code. > > > It seems to me that 1 vs 2 difference can be expressed via bpf program logic > > > instead of return code. > > > > > > How about we do what all other cgroup-bpf progs do: > > > "any no is no. all yes is yes" > > > Meaning any ret=0 - EPERM back to user. > > > If all are ret=1 - kernel handles get/set. > > > > > > I think the desire to differentiate 1 vs 2 came from ordering issue > > > on getsockopt. > > > How about for setsockopt all progs run first and then kernel. > > > For getsockopt kernel runs first and then all progs. > > > Then progs will have an ability to overwrite anything the kernel returns. > > Good idea, makes sense. For getsockopt we'd also need to pass the return > > value of the kernel getsockopt to let bpf programs override it, but seems > > doable. Let me play with it a bit; I'll send another version if nothing > > major comes up. > > > > Thanks for another round of review! > One clarification: we'd still probably need to have 3 return codes for > setsockopt: > * any 0 - EPERM > * all 1 - continue with the kernel path (i.e. apply this sockopt as is) > * any 2 - return after all BPF hooks are executed (bypass kernel) > (any 0 trumps any 2 -> EPERM) > > The context is readonly for setsockopt, so it shouldn't be an issue. > Let me know if you have better idea how to handle that. I think we don't really need 2. The progs can reduce optlen to zero (or optname to BPF_EMPTY_SOCKOPT) and do ret=1. Then the kernel can see that nothing to be be done and return 0 to user space. Since parent prog in the chain will be able to see that child prog set optlen to zero, it will be able to overwrite if necessary. getsockopt wil be clean as well. all 1s return whatever was produced by progs to user space. and progs will be able to see what kernel wanted to return because the kernel's getsockopt logic ran first. ret=2 doesn't have any meaning for getsockopt, so nice to keep setsockopt symmetrical and don't do it there either.
On 06/18, Alexei Starovoitov wrote: > On Tue, Jun 18, 2019 at 11:09 AM Stanislav Fomichev <sdf@fomichev.me> wrote: > > > > On 06/18, Stanislav Fomichev wrote: > > > On 06/18, Alexei Starovoitov wrote: > > > > On Mon, Jun 17, 2019 at 11:01:01AM -0700, Stanislav Fomichev wrote: > > > > > Implement new BPF_PROG_TYPE_CGROUP_SOCKOPT program type and > > > > > BPF_CGROUP_{G,S}ETSOCKOPT cgroup hooks. > > > > > > > > > > BPF_CGROUP_SETSOCKOPT get a read-only view of the setsockopt arguments. > > > > > BPF_CGROUP_GETSOCKOPT can modify the supplied buffer. > > > > > Both of them reuse existing PTR_TO_PACKET{,_END} infrastructure. > > > > > > > > > > The buffer memory is pre-allocated (because I don't think there is > > > > > a precedent for working with __user memory from bpf). This might be > > > > > slow to do for each {s,g}etsockopt call, that's why I've added > > > > > __cgroup_bpf_prog_array_is_empty that exits early if there is nothing > > > > > attached to a cgroup. Note, however, that there is a race between > > > > > __cgroup_bpf_prog_array_is_empty and BPF_PROG_RUN_ARRAY where cgroup > > > > > program layout might have changed; this should not be a problem > > > > > because in general there is a race between multiple calls to > > > > > {s,g}etsocktop and user adding/removing bpf progs from a cgroup. > > > > > > > > > > The return code of the BPF program is handled as follows: > > > > > * 0: EPERM > > > > > * 1: success, execute kernel {s,g}etsockopt path after BPF prog exits > > > > > * 2: success, do _not_ execute kernel {s,g}etsockopt path after BPF > > > > > prog exits > > > > > > > > > > Note that if 0 or 2 is returned from BPF program, no further BPF program > > > > > in the cgroup hierarchy is executed. This is in contrast with any existing > > > > > per-cgroup BPF attach_type. > > > > > > > > This is drastically different from all other cgroup-bpf progs. > > > > I think all programs should be executed regardless of return code. > > > > It seems to me that 1 vs 2 difference can be expressed via bpf program logic > > > > instead of return code. > > > > > > > > How about we do what all other cgroup-bpf progs do: > > > > "any no is no. all yes is yes" > > > > Meaning any ret=0 - EPERM back to user. > > > > If all are ret=1 - kernel handles get/set. > > > > > > > > I think the desire to differentiate 1 vs 2 came from ordering issue > > > > on getsockopt. > > > > How about for setsockopt all progs run first and then kernel. > > > > For getsockopt kernel runs first and then all progs. > > > > Then progs will have an ability to overwrite anything the kernel returns. > > > Good idea, makes sense. For getsockopt we'd also need to pass the return > > > value of the kernel getsockopt to let bpf programs override it, but seems > > > doable. Let me play with it a bit; I'll send another version if nothing > > > major comes up. > > > > > > Thanks for another round of review! > > One clarification: we'd still probably need to have 3 return codes for > > setsockopt: > > * any 0 - EPERM > > * all 1 - continue with the kernel path (i.e. apply this sockopt as is) > > * any 2 - return after all BPF hooks are executed (bypass kernel) > > (any 0 trumps any 2 -> EPERM) > > > > The context is readonly for setsockopt, so it shouldn't be an issue. > > Let me know if you have better idea how to handle that. > > I think we don't really need 2. > The progs can reduce optlen to zero (or optname to BPF_EMPTY_SOCKOPT) > and do ret=1. > Then the kernel can see that nothing to be be done and return 0 to user space. > Since parent prog in the chain will be able to see that child prog > set optlen to zero, it will be able to overwrite if necessary. Ack, optlen=0 sounds good. In that case parent prog can poke into optval because optval_end still points to the valid end of the data (and, as you said, can override optlen back if necessary). Thanks! > getsockopt wil be clean as well. > all 1s return whatever was produced by progs to user space. > and progs will be able to see what kernel wanted to return because > the kernel's getsockopt logic ran first. > ret=2 doesn't have any meaning for getsockopt, so nice to keep > setsockopt symmetrical and don't do it there either. Agreed.
diff --git a/include/linux/bpf-cgroup.h b/include/linux/bpf-cgroup.h index b631ee75762d..406f1ba82531 100644 --- a/include/linux/bpf-cgroup.h +++ b/include/linux/bpf-cgroup.h @@ -124,6 +124,13 @@ int __cgroup_bpf_run_filter_sysctl(struct ctl_table_header *head, loff_t *ppos, void **new_buf, enum bpf_attach_type type); +int __cgroup_bpf_run_filter_setsockopt(struct sock *sock, int level, + int optname, char __user *optval, + unsigned int optlen); +int __cgroup_bpf_run_filter_getsockopt(struct sock *sock, int level, + int optname, char __user *optval, + int __user *optlen); + static inline enum bpf_cgroup_storage_type cgroup_storage_type( struct bpf_map *map) { @@ -280,6 +287,26 @@ int bpf_percpu_cgroup_storage_update(struct bpf_map *map, void *key, __ret; \ }) +#define BPF_CGROUP_RUN_PROG_SETSOCKOPT(sock, level, optname, optval, optlen) \ +({ \ + int __ret = 0; \ + if (cgroup_bpf_enabled) \ + __ret = __cgroup_bpf_run_filter_setsockopt(sock, level, \ + optname, optval, \ + optlen); \ + __ret; \ +}) + +#define BPF_CGROUP_RUN_PROG_GETSOCKOPT(sock, level, optname, optval, optlen) \ +({ \ + int __ret = 0; \ + if (cgroup_bpf_enabled) \ + __ret = __cgroup_bpf_run_filter_getsockopt(sock, level, \ + optname, optval, \ + optlen); \ + __ret; \ +}) + int cgroup_bpf_prog_attach(const union bpf_attr *attr, enum bpf_prog_type ptype, struct bpf_prog *prog); int cgroup_bpf_prog_detach(const union bpf_attr *attr, @@ -349,6 +376,8 @@ static inline int bpf_percpu_cgroup_storage_update(struct bpf_map *map, #define BPF_CGROUP_RUN_PROG_SOCK_OPS(sock_ops) ({ 0; }) #define BPF_CGROUP_RUN_PROG_DEVICE_CGROUP(type,major,minor,access) ({ 0; }) #define BPF_CGROUP_RUN_PROG_SYSCTL(head,table,write,buf,count,pos,nbuf) ({ 0; }) +#define BPF_CGROUP_RUN_PROG_GETSOCKOPT(sock, level, optname, optval, optlen) ({ 0; }) +#define BPF_CGROUP_RUN_PROG_SETSOCKOPT(sock, level, optname, optval, optlen) ({ 0; }) #define for_each_cgroup_storage_type(stype) for (; false; ) diff --git a/include/linux/bpf.h b/include/linux/bpf.h index b15fb5fcb741..70d681dde253 100644 --- a/include/linux/bpf.h +++ b/include/linux/bpf.h @@ -521,6 +521,7 @@ struct bpf_prog_array { struct bpf_prog_array *bpf_prog_array_alloc(u32 prog_cnt, gfp_t flags); void bpf_prog_array_free(struct bpf_prog_array *progs); int bpf_prog_array_length(struct bpf_prog_array *progs); +bool bpf_prog_array_is_empty(struct bpf_prog_array *array); int bpf_prog_array_copy_to_user(struct bpf_prog_array *progs, __u32 __user *prog_ids, u32 cnt); @@ -607,6 +608,50 @@ _out: \ _ret; \ }) +/* To be used by BPF_PROG_TYPE_CGROUP_SOCKOPT program type. + * + * Expected BPF program return values are: + * 0: return -EPERM to the userspace + * 1: sockopt was not handled by BPF, kernel or next BPF prog should do it + * 2: sockopt was handled by BPF, kernel should _not_ do it and return + * to the userspace instead + * + * Note that as soon as BPF program returns 0 or 2 no further + * BPF program is executed and control is returned to the + * userspace. + * + * The macro itself returns: + * 0: sockopt was not handled by BPF, kernel should do it + * 1: sockopt was handled by BPF, kernel should _not_ do it + * -EPERM: return error back to userspace + */ +#define BPF_PROG_CGROUP_SOCKOPT_RUN_ARRAY(array, ctx, func) \ + ({ \ + struct bpf_prog_array_item *_item; \ + struct bpf_prog_array *_array; \ + struct bpf_prog *_prog; \ + u32 _success = 1; \ + u32 _bypass = 0; \ + u32 ret; \ + preempt_disable(); \ + rcu_read_lock(); \ + _array = rcu_dereference(array); \ + _item = &_array->items[0]; \ + while ((_prog = READ_ONCE(_item->prog))) { \ + bpf_cgroup_storage_set(_item->cgroup_storage); \ + ret = func(_prog, ctx); \ + _success &= (ret > 0); \ + _bypass |= (ret == 2); \ + if (ret != 1) \ + break; \ + _item++; \ + } \ + rcu_read_unlock(); \ + preempt_enable(); \ + ret = _success ? _bypass : -EPERM; \ + ret; \ + }) + #define BPF_PROG_RUN_ARRAY(array, ctx, func) \ __BPF_PROG_RUN_ARRAY(array, ctx, func, false) @@ -1055,6 +1100,7 @@ extern const struct bpf_func_proto bpf_spin_unlock_proto; extern const struct bpf_func_proto bpf_get_local_storage_proto; extern const struct bpf_func_proto bpf_strtol_proto; extern const struct bpf_func_proto bpf_strtoul_proto; +extern const struct bpf_func_proto bpf_tcp_sock_proto; /* Shared helpers among cBPF and eBPF. */ void bpf_user_rnd_init_once(void); diff --git a/include/linux/bpf_types.h b/include/linux/bpf_types.h index 5a9975678d6f..eec5aeeeaf92 100644 --- a/include/linux/bpf_types.h +++ b/include/linux/bpf_types.h @@ -30,6 +30,7 @@ BPF_PROG_TYPE(BPF_PROG_TYPE_RAW_TRACEPOINT_WRITABLE, raw_tracepoint_writable) #ifdef CONFIG_CGROUP_BPF BPF_PROG_TYPE(BPF_PROG_TYPE_CGROUP_DEVICE, cg_dev) BPF_PROG_TYPE(BPF_PROG_TYPE_CGROUP_SYSCTL, cg_sysctl) +BPF_PROG_TYPE(BPF_PROG_TYPE_CGROUP_SOCKOPT, cg_sockopt) #endif #ifdef CONFIG_BPF_LIRC_MODE2 BPF_PROG_TYPE(BPF_PROG_TYPE_LIRC_MODE2, lirc_mode2) diff --git a/include/linux/filter.h b/include/linux/filter.h index 43b45d6db36d..6e64d01e4e36 100644 --- a/include/linux/filter.h +++ b/include/linux/filter.h @@ -1199,4 +1199,17 @@ struct bpf_sysctl_kern { u64 tmp_reg; }; +struct bpf_sockopt_kern { + struct sock *sk; + u8 *optval; + u8 *optval_end; + s32 level; + s32 optname; + u32 optlen; + + /* Small on-stack optval buffer to avoid small allocations. + */ + u8 buf[64] __aligned(8); +}; + #endif /* __LINUX_FILTER_H__ */ diff --git a/include/uapi/linux/bpf.h b/include/uapi/linux/bpf.h index d0a23476f887..1cc40a2b6bef 100644 --- a/include/uapi/linux/bpf.h +++ b/include/uapi/linux/bpf.h @@ -170,6 +170,7 @@ enum bpf_prog_type { BPF_PROG_TYPE_FLOW_DISSECTOR, BPF_PROG_TYPE_CGROUP_SYSCTL, BPF_PROG_TYPE_RAW_TRACEPOINT_WRITABLE, + BPF_PROG_TYPE_CGROUP_SOCKOPT, }; enum bpf_attach_type { @@ -192,6 +193,8 @@ enum bpf_attach_type { BPF_LIRC_MODE2, BPF_FLOW_DISSECTOR, BPF_CGROUP_SYSCTL, + BPF_CGROUP_GETSOCKOPT, + BPF_CGROUP_SETSOCKOPT, __MAX_BPF_ATTACH_TYPE }; @@ -3539,4 +3542,14 @@ struct bpf_sysctl { */ }; +struct bpf_sockopt { + __bpf_md_ptr(struct bpf_sock *, sk); + __bpf_md_ptr(void *, optval); + __bpf_md_ptr(void *, optval_end); + + __s32 level; + __s32 optname; + __u32 optlen; +}; + #endif /* _UAPI__LINUX_BPF_H__ */ diff --git a/kernel/bpf/cgroup.c b/kernel/bpf/cgroup.c index 1b65ab0df457..9085a218a1a8 100644 --- a/kernel/bpf/cgroup.c +++ b/kernel/bpf/cgroup.c @@ -18,6 +18,7 @@ #include <linux/bpf.h> #include <linux/bpf-cgroup.h> #include <net/sock.h> +#include <net/bpf_sk_storage.h> DEFINE_STATIC_KEY_FALSE(cgroup_bpf_enabled_key); EXPORT_SYMBOL(cgroup_bpf_enabled_key); @@ -924,6 +925,140 @@ int __cgroup_bpf_run_filter_sysctl(struct ctl_table_header *head, } EXPORT_SYMBOL(__cgroup_bpf_run_filter_sysctl); +static bool __cgroup_bpf_prog_array_is_empty(struct cgroup *cgrp, + enum bpf_attach_type attach_type) +{ + struct bpf_prog_array *prog_array; + bool empty; + + rcu_read_lock(); + prog_array = rcu_dereference(cgrp->bpf.effective[attach_type]); + empty = bpf_prog_array_is_empty(prog_array); + rcu_read_unlock(); + + return empty; +} + +static int sockopt_alloc_buf(struct bpf_sockopt_kern *ctx, int max_optlen) +{ + if (unlikely(max_optlen > PAGE_SIZE)) + return -EINVAL; + + if (likely(max_optlen <= sizeof(ctx->buf))) { + ctx->optval = ctx->buf; + } else { + ctx->optval = kzalloc(max_optlen, GFP_USER); + if (!ctx->optval) + return -ENOMEM; + } + + ctx->optval_end = ctx->optval + max_optlen; + ctx->optlen = max_optlen; + + return 0; +} + +static void sockopt_free_buf(struct bpf_sockopt_kern *ctx) +{ + if (unlikely(ctx->optval != ctx->buf)) + kfree(ctx->optval); +} + +int __cgroup_bpf_run_filter_setsockopt(struct sock *sk, int level, + int optname, char __user *optval, + unsigned int optlen) +{ + struct cgroup *cgrp = sock_cgroup_ptr(&sk->sk_cgrp_data); + struct bpf_sockopt_kern ctx = { + .sk = sk, + .level = level, + .optname = optname, + }; + int ret; + + /* Opportunistic check to see whether we have any BPF program + * attached to the hook so we don't waste time allocating + * memory and locking the socket. + */ + if (__cgroup_bpf_prog_array_is_empty(cgrp, BPF_CGROUP_SETSOCKOPT)) + return 0; + + ret = sockopt_alloc_buf(&ctx, optlen); + if (ret) + return ret; + + if (copy_from_user(ctx.optval, optval, optlen) != 0) { + sockopt_free_buf(&ctx); + return -EFAULT; + } + + lock_sock(sk); + ret = BPF_PROG_CGROUP_SOCKOPT_RUN_ARRAY( + cgrp->bpf.effective[BPF_CGROUP_SETSOCKOPT], + &ctx, BPF_PROG_RUN); + release_sock(sk); + + sockopt_free_buf(&ctx); + + return ret; +} +EXPORT_SYMBOL(__cgroup_bpf_run_filter_setsockopt); + +int __cgroup_bpf_run_filter_getsockopt(struct sock *sk, int level, + int optname, char __user *optval, + int __user *optlen) +{ + struct cgroup *cgrp = sock_cgroup_ptr(&sk->sk_cgrp_data); + struct bpf_sockopt_kern ctx = { + .sk = sk, + .level = level, + .optname = optname, + }; + int max_optlen; + int ret; + + /* Opportunistic check to see whether we have any BPF program + * attached to the hook so we don't waste time allocating + * memory and locking the socket. + */ + if (__cgroup_bpf_prog_array_is_empty(cgrp, BPF_CGROUP_GETSOCKOPT)) + return 0; + + if (get_user(max_optlen, optlen)) + return -EFAULT; + + ret = sockopt_alloc_buf(&ctx, max_optlen); + if (ret) + return ret; + + lock_sock(sk); + ret = BPF_PROG_CGROUP_SOCKOPT_RUN_ARRAY( + cgrp->bpf.effective[BPF_CGROUP_GETSOCKOPT], + &ctx, BPF_PROG_RUN); + release_sock(sk); + + if (ret < 0) + goto out; + + if (ctx.optlen > max_optlen) { + ret = -EFAULT; + goto out; + } + + if (ret) { + if (copy_to_user(optval, ctx.optval, ctx.optlen) || + put_user(ctx.optlen, optlen)) { + ret = -EFAULT; + goto out; + } + } + +out: + sockopt_free_buf(&ctx); + return ret; +} +EXPORT_SYMBOL(__cgroup_bpf_run_filter_getsockopt); + static ssize_t sysctl_cpy_dir(const struct ctl_dir *dir, char **bufp, size_t *lenp) { @@ -1184,3 +1319,128 @@ const struct bpf_verifier_ops cg_sysctl_verifier_ops = { const struct bpf_prog_ops cg_sysctl_prog_ops = { }; + +static const struct bpf_func_proto * +cg_sockopt_func_proto(enum bpf_func_id func_id, const struct bpf_prog *prog) +{ + switch (func_id) { + case BPF_FUNC_sk_storage_get: + return &bpf_sk_storage_get_proto; + case BPF_FUNC_sk_storage_delete: + return &bpf_sk_storage_delete_proto; +#ifdef CONFIG_INET + case BPF_FUNC_tcp_sock: + return &bpf_tcp_sock_proto; +#endif + default: + return cgroup_base_func_proto(func_id, prog); + } +} + +static bool cg_sockopt_is_valid_access(int off, int size, + enum bpf_access_type type, + const struct bpf_prog *prog, + struct bpf_insn_access_aux *info) +{ + const int size_default = sizeof(__u32); + + if (off < 0 || off >= sizeof(struct bpf_sockopt)) + return false; + + if (off % size != 0) + return false; + + if (type == BPF_WRITE) { + switch (off) { + case offsetof(struct bpf_sockopt, optlen): + if (size != size_default) + return false; + return prog->expected_attach_type == + BPF_CGROUP_GETSOCKOPT; + default: + return false; + } + } + + switch (off) { + case offsetof(struct bpf_sockopt, sk): + if (size != sizeof(__u64)) + return false; + info->reg_type = PTR_TO_SOCKET; + break; + case offsetof(struct bpf_sockopt, optval): + if (size != sizeof(__u64)) + return false; + info->reg_type = PTR_TO_PACKET; + break; + case offsetof(struct bpf_sockopt, optval_end): + if (size != sizeof(__u64)) + return false; + info->reg_type = PTR_TO_PACKET_END; + break; + default: + if (size != size_default) + return false; + break; + } + return true; +} + +#define CG_SOCKOPT_ACCESS_FIELD(T, F) \ + T(BPF_FIELD_SIZEOF(struct bpf_sockopt_kern, F), \ + si->dst_reg, si->src_reg, \ + offsetof(struct bpf_sockopt_kern, F)) + +static u32 cg_sockopt_convert_ctx_access(enum bpf_access_type type, + const struct bpf_insn *si, + struct bpf_insn *insn_buf, + struct bpf_prog *prog, + u32 *target_size) +{ + struct bpf_insn *insn = insn_buf; + + switch (si->off) { + case offsetof(struct bpf_sockopt, sk): + *insn++ = CG_SOCKOPT_ACCESS_FIELD(BPF_LDX_MEM, sk); + break; + case offsetof(struct bpf_sockopt, level): + *insn++ = CG_SOCKOPT_ACCESS_FIELD(BPF_LDX_MEM, level); + break; + case offsetof(struct bpf_sockopt, optname): + *insn++ = CG_SOCKOPT_ACCESS_FIELD(BPF_LDX_MEM, optname); + break; + case offsetof(struct bpf_sockopt, optlen): + if (type == BPF_WRITE) + *insn++ = CG_SOCKOPT_ACCESS_FIELD(BPF_STX_MEM, optlen); + else + *insn++ = CG_SOCKOPT_ACCESS_FIELD(BPF_LDX_MEM, optlen); + break; + case offsetof(struct bpf_sockopt, optval): + *insn++ = CG_SOCKOPT_ACCESS_FIELD(BPF_LDX_MEM, optval); + break; + case offsetof(struct bpf_sockopt, optval_end): + *insn++ = CG_SOCKOPT_ACCESS_FIELD(BPF_LDX_MEM, optval_end); + break; + } + + return insn - insn_buf; +} + +static int cg_sockopt_get_prologue(struct bpf_insn *insn_buf, + bool direct_write, + const struct bpf_prog *prog) +{ + /* Nothing to do for sockopt argument. The data is kzalloc'ated. + */ + return 0; +} + +const struct bpf_verifier_ops cg_sockopt_verifier_ops = { + .get_func_proto = cg_sockopt_func_proto, + .is_valid_access = cg_sockopt_is_valid_access, + .convert_ctx_access = cg_sockopt_convert_ctx_access, + .gen_prologue = cg_sockopt_get_prologue, +}; + +const struct bpf_prog_ops cg_sockopt_prog_ops = { +}; diff --git a/kernel/bpf/core.c b/kernel/bpf/core.c index 33fb292f2e30..e9152ebd66bc 100644 --- a/kernel/bpf/core.c +++ b/kernel/bpf/core.c @@ -1813,6 +1813,15 @@ int bpf_prog_array_length(struct bpf_prog_array *array) return cnt; } +bool bpf_prog_array_is_empty(struct bpf_prog_array *array) +{ + struct bpf_prog_array_item *item; + + for (item = array->items; item->prog; item++) + if (item->prog != &dummy_bpf_prog.prog) + return false; + return true; +} static bool bpf_prog_array_copy_core(struct bpf_prog_array *array, u32 *prog_ids, diff --git a/kernel/bpf/syscall.c b/kernel/bpf/syscall.c index 4c53cbd3329d..4ad2b5f1905f 100644 --- a/kernel/bpf/syscall.c +++ b/kernel/bpf/syscall.c @@ -1596,6 +1596,14 @@ bpf_prog_load_check_attach_type(enum bpf_prog_type prog_type, default: return -EINVAL; } + case BPF_PROG_TYPE_CGROUP_SOCKOPT: + switch (expected_attach_type) { + case BPF_CGROUP_SETSOCKOPT: + case BPF_CGROUP_GETSOCKOPT: + return 0; + default: + return -EINVAL; + } default: return 0; } @@ -1846,6 +1854,7 @@ static int bpf_prog_attach_check_attach_type(const struct bpf_prog *prog, switch (prog->type) { case BPF_PROG_TYPE_CGROUP_SOCK: case BPF_PROG_TYPE_CGROUP_SOCK_ADDR: + case BPF_PROG_TYPE_CGROUP_SOCKOPT: return attach_type == prog->expected_attach_type ? 0 : -EINVAL; case BPF_PROG_TYPE_CGROUP_SKB: return prog->enforce_expected_attach_type && @@ -1916,6 +1925,10 @@ static int bpf_prog_attach(const union bpf_attr *attr) case BPF_CGROUP_SYSCTL: ptype = BPF_PROG_TYPE_CGROUP_SYSCTL; break; + case BPF_CGROUP_GETSOCKOPT: + case BPF_CGROUP_SETSOCKOPT: + ptype = BPF_PROG_TYPE_CGROUP_SOCKOPT; + break; default: return -EINVAL; } @@ -1997,6 +2010,10 @@ static int bpf_prog_detach(const union bpf_attr *attr) case BPF_CGROUP_SYSCTL: ptype = BPF_PROG_TYPE_CGROUP_SYSCTL; break; + case BPF_CGROUP_GETSOCKOPT: + case BPF_CGROUP_SETSOCKOPT: + ptype = BPF_PROG_TYPE_CGROUP_SOCKOPT; + break; default: return -EINVAL; } @@ -2031,6 +2048,8 @@ static int bpf_prog_query(const union bpf_attr *attr, case BPF_CGROUP_SOCK_OPS: case BPF_CGROUP_DEVICE: case BPF_CGROUP_SYSCTL: + case BPF_CGROUP_GETSOCKOPT: + case BPF_CGROUP_SETSOCKOPT: break; case BPF_LIRC_MODE2: return lirc_prog_query(attr, uattr); diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c index 8d1786357a09..f03b00b4c1b7 100644 --- a/kernel/bpf/verifier.c +++ b/kernel/bpf/verifier.c @@ -1720,6 +1720,18 @@ static bool may_access_direct_pkt_data(struct bpf_verifier_env *env, env->seen_direct_write = true; return true; + + case BPF_PROG_TYPE_CGROUP_SOCKOPT: + if (t == BPF_WRITE) { + if (env->prog->expected_attach_type == + BPF_CGROUP_GETSOCKOPT) { + env->seen_direct_write = true; + return true; + } + return false; + } + return true; + default: return false; } @@ -5541,6 +5553,9 @@ static int check_return_code(struct bpf_verifier_env *env) case BPF_PROG_TYPE_CGROUP_DEVICE: case BPF_PROG_TYPE_CGROUP_SYSCTL: break; + case BPF_PROG_TYPE_CGROUP_SOCKOPT: + range = tnum_range(0, 2); + break; default: return 0; } diff --git a/net/core/filter.c b/net/core/filter.c index 8c18f2781afa..e2ad8144cf6e 100644 --- a/net/core/filter.c +++ b/net/core/filter.c @@ -5636,7 +5636,7 @@ BPF_CALL_1(bpf_tcp_sock, struct sock *, sk) return (unsigned long)NULL; } -static const struct bpf_func_proto bpf_tcp_sock_proto = { +const struct bpf_func_proto bpf_tcp_sock_proto = { .func = bpf_tcp_sock, .gpl_only = false, .ret_type = RET_PTR_TO_TCP_SOCK_OR_NULL, diff --git a/net/socket.c b/net/socket.c index 72372dc5dd70..e8654f1f70e6 100644 --- a/net/socket.c +++ b/net/socket.c @@ -2069,6 +2069,15 @@ static int __sys_setsockopt(int fd, int level, int optname, if (err) goto out_put; + err = BPF_CGROUP_RUN_PROG_SETSOCKOPT(sock->sk, level, optname, + optval, optlen); + if (err < 0) { + goto out_put; + } else if (err > 0) { + err = 0; + goto out_put; + } + if (level == SOL_SOCKET) err = sock_setsockopt(sock, level, optname, optval, @@ -2106,6 +2115,15 @@ static int __sys_getsockopt(int fd, int level, int optname, if (err) goto out_put; + err = BPF_CGROUP_RUN_PROG_GETSOCKOPT(sock->sk, level, optname, + optval, optlen); + if (err < 0) { + goto out_put; + } else if (err > 0) { + err = 0; + goto out_put; + } + if (level == SOL_SOCKET) err = sock_getsockopt(sock, level, optname, optval,
Implement new BPF_PROG_TYPE_CGROUP_SOCKOPT program type and BPF_CGROUP_{G,S}ETSOCKOPT cgroup hooks. BPF_CGROUP_SETSOCKOPT get a read-only view of the setsockopt arguments. BPF_CGROUP_GETSOCKOPT can modify the supplied buffer. Both of them reuse existing PTR_TO_PACKET{,_END} infrastructure. The buffer memory is pre-allocated (because I don't think there is a precedent for working with __user memory from bpf). This might be slow to do for each {s,g}etsockopt call, that's why I've added __cgroup_bpf_prog_array_is_empty that exits early if there is nothing attached to a cgroup. Note, however, that there is a race between __cgroup_bpf_prog_array_is_empty and BPF_PROG_RUN_ARRAY where cgroup program layout might have changed; this should not be a problem because in general there is a race between multiple calls to {s,g}etsocktop and user adding/removing bpf progs from a cgroup. The return code of the BPF program is handled as follows: * 0: EPERM * 1: success, execute kernel {s,g}etsockopt path after BPF prog exits * 2: success, do _not_ execute kernel {s,g}etsockopt path after BPF prog exits Note that if 0 or 2 is returned from BPF program, no further BPF program in the cgroup hierarchy is executed. This is in contrast with any existing per-cgroup BPF attach_type. v6: * rework cgroup chaining; stop as soon as bpf program returns 0 or 2; see patch with the documentation for the details * drop Andrii's and Martin's Acked-by (not sure they are comfortable with the new state of things) v5: * skip copy_to_user() and put_user() when ret == 0 (Martin Lau) v4: * don't export bpf_sk_fullsock helper (Martin Lau) * size != sizeof(__u64) for uapi pointers (Martin Lau) * offsetof instead of bpf_ctx_range when checking ctx access (Martin Lau) v3: * typos in BPF_PROG_CGROUP_SOCKOPT_RUN_ARRAY comments (Andrii Nakryiko) * reverse christmas tree in BPF_PROG_CGROUP_SOCKOPT_RUN_ARRAY (Andrii Nakryiko) * use __bpf_md_ptr instead of __u32 for optval{,_end} (Martin Lau) * use BPF_FIELD_SIZEOF() for consistency (Martin Lau) * new CG_SOCKOPT_ACCESS macro to wrap repeated parts v2: * moved bpf_sockopt_kern fields around to remove a hole (Martin Lau) * aligned bpf_sockopt_kern->buf to 8 bytes (Martin Lau) * bpf_prog_array_is_empty instead of bpf_prog_array_length (Martin Lau) * added [0,2] return code check to verifier (Martin Lau) * dropped unused buf[64] from the stack (Martin Lau) * use PTR_TO_SOCKET for bpf_sockopt->sk (Martin Lau) * dropped bpf_target_off from ctx rewrites (Martin Lau) * use return code for kernel bypass (Martin Lau & Andrii Nakryiko) Cc: Martin Lau <kafai@fb.com> Signed-off-by: Stanislav Fomichev <sdf@google.com> --- include/linux/bpf-cgroup.h | 29 +++++ include/linux/bpf.h | 46 +++++++ include/linux/bpf_types.h | 1 + include/linux/filter.h | 13 ++ include/uapi/linux/bpf.h | 13 ++ kernel/bpf/cgroup.c | 260 +++++++++++++++++++++++++++++++++++++ kernel/bpf/core.c | 9 ++ kernel/bpf/syscall.c | 19 +++ kernel/bpf/verifier.c | 15 +++ net/core/filter.c | 2 +- net/socket.c | 18 +++ 11 files changed, 424 insertions(+), 1 deletion(-)