| Message ID | 20200715233634.3868-3-maciej.fijalkowski@intel.com |
|---|---|
| State | Changes Requested |
| Delegated to: | BPF Maintainers |
| Headers | show |
| Series | bpf: tailcalls in BPF subprograms | expand |
On 7/16/20 1:36 AM, Maciej Fijalkowski wrote: > Relax verifier's restriction that was meant to forbid tailcall usage > when subprog count was higher than 1. > > Also, do not max out the stack depth of program that utilizes tailcalls. > > Signed-off-by: Maciej Fijalkowski <maciej.fijalkowski@intel.com> [nit: this patch also needs reordering]
On 7/16/20 1:36 AM, Maciej Fijalkowski wrote: > Relax verifier's restriction that was meant to forbid tailcall usage > when subprog count was higher than 1. > > Also, do not max out the stack depth of program that utilizes tailcalls. > > Signed-off-by: Maciej Fijalkowski <maciej.fijalkowski@intel.com> > --- > kernel/bpf/verifier.c | 5 ----- > 1 file changed, 5 deletions(-) > > diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c > index 3c1efc9d08fd..6481342b31ba 100644 > --- a/kernel/bpf/verifier.c > +++ b/kernel/bpf/verifier.c > @@ -4172,10 +4172,6 @@ static int check_map_func_compatibility(struct bpf_verifier_env *env, > case BPF_FUNC_tail_call: > if (map->map_type != BPF_MAP_TYPE_PROG_ARRAY) > goto error; > - if (env->subprog_cnt > 1) { > - verbose(env, "tail_calls are not allowed in programs with bpf-to-bpf calls\n"); > - return -EINVAL; > - } > break; > case BPF_FUNC_perf_event_read: > case BPF_FUNC_perf_event_output: > @@ -10252,7 +10248,6 @@ static int fixup_bpf_calls(struct bpf_verifier_env *env) > * the program array. > */ > prog->cb_access = 1; > - env->prog->aux->stack_depth = MAX_BPF_STACK; > env->prog->aux->max_pkt_offset = MAX_PACKET_OFF; > > /* mark bpf_tail_call as different opcode to avoid Also, isn't this broken when JIT is not used (as in stack oob access)?
On 7/16/20 11:29 PM, Daniel Borkmann wrote: > On 7/16/20 1:36 AM, Maciej Fijalkowski wrote: >> Relax verifier's restriction that was meant to forbid tailcall usage >> when subprog count was higher than 1. >> >> Also, do not max out the stack depth of program that utilizes tailcalls. >> >> Signed-off-by: Maciej Fijalkowski <maciej.fijalkowski@intel.com> >> --- >> kernel/bpf/verifier.c | 5 ----- >> 1 file changed, 5 deletions(-) >> >> diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c >> index 3c1efc9d08fd..6481342b31ba 100644 >> --- a/kernel/bpf/verifier.c >> +++ b/kernel/bpf/verifier.c >> @@ -4172,10 +4172,6 @@ static int check_map_func_compatibility(struct bpf_verifier_env *env, >> case BPF_FUNC_tail_call: >> if (map->map_type != BPF_MAP_TYPE_PROG_ARRAY) >> goto error; >> - if (env->subprog_cnt > 1) { >> - verbose(env, "tail_calls are not allowed in programs with bpf-to-bpf calls\n"); >> - return -EINVAL; >> - } >> break; >> case BPF_FUNC_perf_event_read: >> case BPF_FUNC_perf_event_output: >> @@ -10252,7 +10248,6 @@ static int fixup_bpf_calls(struct bpf_verifier_env *env) >> * the program array. >> */ >> prog->cb_access = 1; >> - env->prog->aux->stack_depth = MAX_BPF_STACK; >> env->prog->aux->max_pkt_offset = MAX_PACKET_OFF; >> /* mark bpf_tail_call as different opcode to avoid > > Also, isn't this broken when JIT is not used (as in stack oob access)? (Similarly for non-x86 archs after this set.)
On Fri, Jul 17, 2020 at 1:12 AM Daniel Borkmann <daniel@iogearbox.net> wrote: > > On 7/16/20 11:29 PM, Daniel Borkmann wrote: > > On 7/16/20 1:36 AM, Maciej Fijalkowski wrote: > >> Relax verifier's restriction that was meant to forbid tailcall usage > >> when subprog count was higher than 1. > >> > >> Also, do not max out the stack depth of program that utilizes tailcalls. > >> > >> Signed-off-by: Maciej Fijalkowski <maciej.fijalkowski@intel.com> > >> --- > >> kernel/bpf/verifier.c | 5 ----- > >> 1 file changed, 5 deletions(-) > >> > >> diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c > >> index 3c1efc9d08fd..6481342b31ba 100644 > >> --- a/kernel/bpf/verifier.c > >> +++ b/kernel/bpf/verifier.c > >> @@ -4172,10 +4172,6 @@ static int check_map_func_compatibility(struct bpf_verifier_env *env, > >> case BPF_FUNC_tail_call: > >> if (map->map_type != BPF_MAP_TYPE_PROG_ARRAY) > >> goto error; > >> - if (env->subprog_cnt > 1) { > >> - verbose(env, "tail_calls are not allowed in programs with bpf-to-bpf calls\n"); > >> - return -EINVAL; > >> - } > >> break; > >> case BPF_FUNC_perf_event_read: > >> case BPF_FUNC_perf_event_output: > >> @@ -10252,7 +10248,6 @@ static int fixup_bpf_calls(struct bpf_verifier_env *env) > >> * the program array. > >> */ > >> prog->cb_access = 1; > >> - env->prog->aux->stack_depth = MAX_BPF_STACK; > >> env->prog->aux->max_pkt_offset = MAX_PACKET_OFF; > >> /* mark bpf_tail_call as different opcode to avoid > > > > Also, isn't this broken when JIT is not used (as in stack oob access)? > > (Similarly for non-x86 archs after this set.) Honestly at this point I'm not sure how to approach it, but as I said I'm in a bit of a rush so probably not thinking clearly :) So in the end we want to allow it *only* for case when underlying arch is the x86-64 and when JIT is turned on, correct? Is this a matter of #define's juggling or how do you see it?
diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c index 3c1efc9d08fd..6481342b31ba 100644 --- a/kernel/bpf/verifier.c +++ b/kernel/bpf/verifier.c @@ -4172,10 +4172,6 @@ static int check_map_func_compatibility(struct bpf_verifier_env *env, case BPF_FUNC_tail_call: if (map->map_type != BPF_MAP_TYPE_PROG_ARRAY) goto error; - if (env->subprog_cnt > 1) { - verbose(env, "tail_calls are not allowed in programs with bpf-to-bpf calls\n"); - return -EINVAL; - } break; case BPF_FUNC_perf_event_read: case BPF_FUNC_perf_event_output: @@ -10252,7 +10248,6 @@ static int fixup_bpf_calls(struct bpf_verifier_env *env) * the program array. */ prog->cb_access = 1; - env->prog->aux->stack_depth = MAX_BPF_STACK; env->prog->aux->max_pkt_offset = MAX_PACKET_OFF; /* mark bpf_tail_call as different opcode to avoid
Relax verifier's restriction that was meant to forbid tailcall usage when subprog count was higher than 1. Also, do not max out the stack depth of program that utilizes tailcalls. Signed-off-by: Maciej Fijalkowski <maciej.fijalkowski@intel.com> --- kernel/bpf/verifier.c | 5 ----- 1 file changed, 5 deletions(-)