| Message ID | 20160822073206.1342-1-cyrilbur@gmail.com (mailing list archive) |
|---|---|
| State | Changes Requested |
| Headers | show |
Hi Cyril, On Mon, Aug 22, 2016 at 05:32:06PM +1000, Cyril Bur wrote: > diff --git a/arch/powerpc/kernel/signal_32.c b/arch/powerpc/kernel/signal_32.c > index b6aa378..31e4e15 100644 > --- a/arch/powerpc/kernel/signal_32.c > +++ b/arch/powerpc/kernel/signal_32.c > @@ -1226,7 +1226,19 @@ long sys_rt_sigreturn(int r3, int r4, int r5, int r6, int r7, int r8, > (regs->gpr[1] + __SIGNAL_FRAMESIZE + 16); > if (!access_ok(VERIFY_READ, rt_sf, sizeof(*rt_sf))) > goto bad; > + > #ifdef CONFIG_PPC_TRANSACTIONAL_MEM > + /* > + * If there is a transactional/suspended state then throw it away. > + * The purpose of a sigreturn is to destroy all traces of the > + * signal frame, this includes any transactional state created > + * within in. > + * The cause is not important as there will never be a > + * recheckpoint so it's not user visible. > + */ > + if (MSR_TM_ACTIVE(mfmsr())) > + tm_reclaim_current(0); > + Maybe a little picky here: Per my understanding, the TRANSACTIONAL state will be failed in system call common entry. The only expected state to prevent here is SUSPEND state. Should we use MSR_TM_SUSPENDED(mfmsr()) here and BUG_ON MSR_TM_TRANSACTIONAL(mfmsr())? -- If it is transactional state, something is wrong with kernel. Others looks good to me. Thanks, - Simon
On Mon, 2016-08-22 at 17:32 +1000, Cyril Bur wrote: The subject prefix should have contained V2. Sorry. > Userspace can begin and suspend a transaction within the signal > handler which means they might enter sys_rt_sigreturn() with the > processor in suspended state. > > sys_rt_sigreturn() wants to restore process context (which may have > been in a transaction before signal delivery). To do this it must > restore TM SPRS. To achieve this, any transaction initiated within > the > signal frame must be discarded in order to be able to restore TM SPRs > as TM SPRs can only be manipulated non-transactionally.. > From the PowerPC ISA: > TM Bad Thing Exception [Category: Transactional Memory] > An attempt is made to execute a mtspr targeting a TM register in > other than Non-transactional state. > > Not doing so results in a TM Bad Thing: > [12045.221359] Kernel BUG at c000000000050a40 [verbose debug info > unavailable] > [12045.221470] Unexpected TM Bad Thing exception at c000000000050a40 > (msr 0x201033) > [12045.221540] Oops: Unrecoverable exception, sig: 6 [#1] > [12045.221586] SMP NR_CPUS=2048 NUMA PowerNV > [12045.221634] Modules linked in: xt_CHECKSUM iptable_mangle > ipt_MASQUERADE > nf_nat_masquerade_ipv4 iptable_nat nf_nat_ipv4 nf_nat > nf_conntrack_ipv4 nf_defrag_ipv4 > xt_conntrack nf_conntrack ipt_REJECT nf_reject_ipv4 xt_tcpudp bridge > stp llc ebtable_filter > ebtables ip6table_filter ip6_tables iptable_filter ip_tables > x_tables kvm_hv kvm > uio_pdrv_genirq ipmi_powernv uio powernv_rng ipmi_msghandler autofs4 > ses enclosure > scsi_transport_sas bnx2x ipr mdio libcrc32c > [12045.222167] CPU: 68 PID: 6178 Comm: sigreturnpanic Not tainted > 4.7.0 #34 > [12045.222224] task: c0000000fce38600 ti: c0000000fceb4000 task.ti: > c0000000fceb4000 > [12045.222293] NIP: c000000000050a40 LR: c0000000000163bc CTR: > 0000000000000000 > [12045.222361] REGS: c0000000fceb7ac0 TRAP: 0700 Not tainted > (4.7.0) > [12045.222418] MSR: 9000000300201033 <SF,HV,ME,IR,DR,RI,LE,TM[SE]> > CR: 28444280 XER: 20000000 > [12045.222625] CFAR: c0000000000163b8 SOFTE: 0 PACATMSCRATCH: > 900000014280f033 > GPR00: 01100000b8000001 c0000000fceb7d40 c00000000139c100 > c0000000fce390d0 > GPR04: 900000034280f033 0000000000000000 0000000000000000 > 0000000000000000 > GPR08: 0000000000000000 b000000000001033 0000000000000001 > 0000000000000000 > GPR12: 0000000000000000 c000000002926400 0000000000000000 > 0000000000000000 > GPR16: 0000000000000000 0000000000000000 0000000000000000 > 0000000000000000 > GPR20: 0000000000000000 0000000000000000 0000000000000000 > 0000000000000000 > GPR24: 0000000000000000 00003ffff98cadd0 00003ffff98cb470 > 0000000000000000 > GPR28: 900000034280f033 c0000000fceb7ea0 0000000000000001 > c0000000fce390d0 > [12045.223535] NIP [c000000000050a40] tm_restore_sprs+0xc/0x1c > [12045.223584] LR [c0000000000163bc] tm_recheckpoint+0x5c/0xa0 > [12045.223630] Call Trace: > [12045.223655] [c0000000fceb7d80] [c000000000026e74] > sys_rt_sigreturn+0x494/0x6c0 > [12045.223738] [c0000000fceb7e30] [c0000000000092e0] > system_call+0x38/0x108 > [12045.223806] Instruction dump: > [12045.223841] 7c800164 4e800020 7c0022a6 f80304a8 7c0222a6 f80304b0 > 7c0122a6 f80304b8 > [12045.223955] 4e800020 e80304a8 7c0023a6 e80304b0 <7c0223a6> > e80304b8 7c0123a6 4e800020 > [12045.224074] ---[ end trace cb8002ee240bae76 ]--- > > It isn't clear exactly if there is really a use case for userspace > returning with a suspended transaction, however, doing so doesn't (on > its own) constitute a bad frame. As such, this patch simply discards > the transactional state of the context calling the sigreturn and > continues. > > Reported-by: Laurent Dufour <ldufour@linux.vnet.ibm.com> > Signed-off-by: Cyril Bur <cyrilbur@gmail.com> > --- > V2: Move the code down into the #ifdef CONFIG_PPC_TRANSACTIONAL_MEM > (32 and 64 bit) > Add a small amount of text to Documentation > Adjust the commit message for clarity > > Documentation/powerpc/transactional_memory.txt | 2 ++ > arch/powerpc/kernel/signal_32.c | 12 ++++++++++++ > arch/powerpc/kernel/signal_64.c | 12 ++++++++++++ > 3 files changed, 26 insertions(+) > > diff --git a/Documentation/powerpc/transactional_memory.txt > b/Documentation/powerpc/transactional_memory.txt > index ba0a2a4..e32fdbb 100644 > --- a/Documentation/powerpc/transactional_memory.txt > +++ b/Documentation/powerpc/transactional_memory.txt > @@ -167,6 +167,8 @@ signal will be rolled back anyway. > For signals taken in non-TM or suspended mode, we use the > normal/non-checkpointed stack pointer. > > +Any transaction initiated inside a sighandler and suspended on > return > +from the sighandler to the kernel will get reclaimed and discarded. > > Failure cause codes used by kernel > ================================== > diff --git a/arch/powerpc/kernel/signal_32.c > b/arch/powerpc/kernel/signal_32.c > index b6aa378..31e4e15 100644 > --- a/arch/powerpc/kernel/signal_32.c > +++ b/arch/powerpc/kernel/signal_32.c > @@ -1226,7 +1226,19 @@ long sys_rt_sigreturn(int r3, int r4, int r5, > int r6, int r7, int r8, > (regs->gpr[1] + __SIGNAL_FRAMESIZE + 16); > if (!access_ok(VERIFY_READ, rt_sf, sizeof(*rt_sf))) > goto bad; > + > #ifdef CONFIG_PPC_TRANSACTIONAL_MEM > + /* > + * If there is a transactional/suspended state then throw it > away. > + * The purpose of a sigreturn is to destroy all traces of > the > + * signal frame, this includes any transactional state > created > + * within in. > + * The cause is not important as there will never be a > + * recheckpoint so it's not user visible. > + */ > + if (MSR_TM_ACTIVE(mfmsr())) > + tm_reclaim_current(0); > + > if (__get_user(tmp, &rt_sf->uc.uc_link)) > goto bad; > uc_transact = (struct ucontext __user *)(uintptr_t)tmp; > diff --git a/arch/powerpc/kernel/signal_64.c > b/arch/powerpc/kernel/signal_64.c > index 7e49984..8425eee 100644 > --- a/arch/powerpc/kernel/signal_64.c > +++ b/arch/powerpc/kernel/signal_64.c > @@ -676,7 +676,19 @@ int sys_rt_sigreturn(unsigned long r3, unsigned > long r4, unsigned long r5, > if (__copy_from_user(&set, &uc->uc_sigmask, sizeof(set))) > goto badframe; > set_current_blocked(&set); > + > #ifdef CONFIG_PPC_TRANSACTIONAL_MEM > + /* > + * If there is a transactional/suspended state then throw it > away. > + * The purpose of a sigreturn is to destroy all traces of > the > + * signal frame, this includes any transactional state > created > + * within in. > + * The cause is not important as there will never be a > + * recheckpoint so it's not user visible. > + */ > + if (MSR_TM_ACTIVE(mfmsr())) > + tm_reclaim_current(0); > + > if (__get_user(msr, &uc->uc_mcontext.gp_regs[PT_MSR])) > goto badframe; > if (MSR_TM_ACTIVE(msr)) {
On 22/08/2016 09:32, Cyril Bur wrote: > Userspace can begin and suspend a transaction within the signal > handler which means they might enter sys_rt_sigreturn() with the > processor in suspended state. > > sys_rt_sigreturn() wants to restore process context (which may have > been in a transaction before signal delivery). To do this it must > restore TM SPRS. To achieve this, any transaction initiated within the > signal frame must be discarded in order to be able to restore TM SPRs > as TM SPRs can only be manipulated non-transactionally.. > From the PowerPC ISA: > TM Bad Thing Exception [Category: Transactional Memory] > An attempt is made to execute a mtspr targeting a TM register in > other than Non-transactional state. > > Not doing so results in a TM Bad Thing: > [12045.221359] Kernel BUG at c000000000050a40 [verbose debug info unavailable] > [12045.221470] Unexpected TM Bad Thing exception at c000000000050a40 (msr 0x201033) > [12045.221540] Oops: Unrecoverable exception, sig: 6 [#1] > [12045.221586] SMP NR_CPUS=2048 NUMA PowerNV > [12045.221634] Modules linked in: xt_CHECKSUM iptable_mangle ipt_MASQUERADE > nf_nat_masquerade_ipv4 iptable_nat nf_nat_ipv4 nf_nat nf_conntrack_ipv4 nf_defrag_ipv4 > xt_conntrack nf_conntrack ipt_REJECT nf_reject_ipv4 xt_tcpudp bridge stp llc ebtable_filter > ebtables ip6table_filter ip6_tables iptable_filter ip_tables x_tables kvm_hv kvm > uio_pdrv_genirq ipmi_powernv uio powernv_rng ipmi_msghandler autofs4 ses enclosure > scsi_transport_sas bnx2x ipr mdio libcrc32c > [12045.222167] CPU: 68 PID: 6178 Comm: sigreturnpanic Not tainted 4.7.0 #34 > [12045.222224] task: c0000000fce38600 ti: c0000000fceb4000 task.ti: c0000000fceb4000 > [12045.222293] NIP: c000000000050a40 LR: c0000000000163bc CTR: 0000000000000000 > [12045.222361] REGS: c0000000fceb7ac0 TRAP: 0700 Not tainted (4.7.0) > [12045.222418] MSR: 9000000300201033 <SF,HV,ME,IR,DR,RI,LE,TM[SE]> CR: 28444280 XER: 20000000 > [12045.222625] CFAR: c0000000000163b8 SOFTE: 0 PACATMSCRATCH: 900000014280f033 > GPR00: 01100000b8000001 c0000000fceb7d40 c00000000139c100 c0000000fce390d0 > GPR04: 900000034280f033 0000000000000000 0000000000000000 0000000000000000 > GPR08: 0000000000000000 b000000000001033 0000000000000001 0000000000000000 > GPR12: 0000000000000000 c000000002926400 0000000000000000 0000000000000000 > GPR16: 0000000000000000 0000000000000000 0000000000000000 0000000000000000 > GPR20: 0000000000000000 0000000000000000 0000000000000000 0000000000000000 > GPR24: 0000000000000000 00003ffff98cadd0 00003ffff98cb470 0000000000000000 > GPR28: 900000034280f033 c0000000fceb7ea0 0000000000000001 c0000000fce390d0 > [12045.223535] NIP [c000000000050a40] tm_restore_sprs+0xc/0x1c > [12045.223584] LR [c0000000000163bc] tm_recheckpoint+0x5c/0xa0 > [12045.223630] Call Trace: > [12045.223655] [c0000000fceb7d80] [c000000000026e74] sys_rt_sigreturn+0x494/0x6c0 > [12045.223738] [c0000000fceb7e30] [c0000000000092e0] system_call+0x38/0x108 > [12045.223806] Instruction dump: > [12045.223841] 7c800164 4e800020 7c0022a6 f80304a8 7c0222a6 f80304b0 7c0122a6 f80304b8 > [12045.223955] 4e800020 e80304a8 7c0023a6 e80304b0 <7c0223a6> e80304b8 7c0123a6 4e800020 > [12045.224074] ---[ end trace cb8002ee240bae76 ]--- > > It isn't clear exactly if there is really a use case for userspace > returning with a suspended transaction, however, doing so doesn't (on > its own) constitute a bad frame. As such, this patch simply discards > the transactional state of the context calling the sigreturn and > continues. > > Reported-by: Laurent Dufour <ldufour@linux.vnet.ibm.com> > Signed-off-by: Cyril Bur <cyrilbur@gmail.com> > --- > V2: Move the code down into the #ifdef CONFIG_PPC_TRANSACTIONAL_MEM (32 and 64 bit) > Add a small amount of text to Documentation > Adjust the commit message for clarity > FWIW, Tested-by: Laurent Dufour <ldufour@linux.vnet.ibm.com>
On Sat, 2016-08-20 at 18:03 +0800, Simon Guo wrote: > Hi Cyril, > On Mon, Aug 22, 2016 at 05:32:06PM +1000, Cyril Bur wrote: > > > > diff --git a/arch/powerpc/kernel/signal_32.c > > b/arch/powerpc/kernel/signal_32.c > > index b6aa378..31e4e15 100644 > > --- a/arch/powerpc/kernel/signal_32.c > > +++ b/arch/powerpc/kernel/signal_32.c > > @@ -1226,7 +1226,19 @@ long sys_rt_sigreturn(int r3, int r4, int > > r5, int r6, int r7, int r8, > > (regs->gpr[1] + __SIGNAL_FRAMESIZE + 16); > > if (!access_ok(VERIFY_READ, rt_sf, sizeof(*rt_sf))) > > goto bad; > > + > > #ifdef CONFIG_PPC_TRANSACTIONAL_MEM > > + /* > > + * If there is a transactional/suspended state then throw > > it away. > > + * The purpose of a sigreturn is to destroy all traces of > > the > > + * signal frame, this includes any transactional state > > created > > + * within in. > > + * The cause is not important as there will never be a > > + * recheckpoint so it's not user visible. > > + */ > > + if (MSR_TM_ACTIVE(mfmsr())) > > + tm_reclaim_current(0); > > + > Maybe a little picky here: > Per my understanding, the TRANSACTIONAL state will be failed in > system > call common entry. The only expected state to prevent here is > SUSPEND > state. That is the case yes. > Should we use MSR_TM_SUSPENDED(mfmsr()) here and BUG_ON > MSR_TM_TRANSACTIONAL(mfmsr())? -- If it is transactional state, > something > is wrong with kernel. > I'm happy to change it to MSR_TM_SUSPENDED. We should decide what the result of getting here with TRANSACTIONAL is. I see two posibilities: 1. the reclaim will solve the problem and we can continue, there is obviously a bug somewhere else but we think it doesn't affect us here and we *hope* it will be contained elsewhere. 2. We think seeing TRANSACTIONAL here means we have a problem that is going to lead to corruption of state such that bad data will propage, in which case I think a BUG_ON() is a good idea. I'm more in favour of 1, there doesn't seem to be any other way to get here but through syscall entry, this kind of bug should probably be caught more generally. In that case I would say that checking ACTIVE is good since we know that we WILL blow up if ACTIVE and we don't do a reclaim. Maybe now that I'm thinking about it, change it to SUSPENDED but no BUG_ON(), as I just said, we'll do a Bad Thing anyway, which will reveal the problem. I have to send another version anyway as it doesn't seem to be working for 32bit. > Others looks good to me. > > Thanks, > - Simon
diff --git a/Documentation/powerpc/transactional_memory.txt b/Documentation/powerpc/transactional_memory.txt index ba0a2a4..e32fdbb 100644 --- a/Documentation/powerpc/transactional_memory.txt +++ b/Documentation/powerpc/transactional_memory.txt @@ -167,6 +167,8 @@ signal will be rolled back anyway. For signals taken in non-TM or suspended mode, we use the normal/non-checkpointed stack pointer. +Any transaction initiated inside a sighandler and suspended on return +from the sighandler to the kernel will get reclaimed and discarded. Failure cause codes used by kernel ================================== diff --git a/arch/powerpc/kernel/signal_32.c b/arch/powerpc/kernel/signal_32.c index b6aa378..31e4e15 100644 --- a/arch/powerpc/kernel/signal_32.c +++ b/arch/powerpc/kernel/signal_32.c @@ -1226,7 +1226,19 @@ long sys_rt_sigreturn(int r3, int r4, int r5, int r6, int r7, int r8, (regs->gpr[1] + __SIGNAL_FRAMESIZE + 16); if (!access_ok(VERIFY_READ, rt_sf, sizeof(*rt_sf))) goto bad; + #ifdef CONFIG_PPC_TRANSACTIONAL_MEM + /* + * If there is a transactional/suspended state then throw it away. + * The purpose of a sigreturn is to destroy all traces of the + * signal frame, this includes any transactional state created + * within in. + * The cause is not important as there will never be a + * recheckpoint so it's not user visible. + */ + if (MSR_TM_ACTIVE(mfmsr())) + tm_reclaim_current(0); + if (__get_user(tmp, &rt_sf->uc.uc_link)) goto bad; uc_transact = (struct ucontext __user *)(uintptr_t)tmp; diff --git a/arch/powerpc/kernel/signal_64.c b/arch/powerpc/kernel/signal_64.c index 7e49984..8425eee 100644 --- a/arch/powerpc/kernel/signal_64.c +++ b/arch/powerpc/kernel/signal_64.c @@ -676,7 +676,19 @@ int sys_rt_sigreturn(unsigned long r3, unsigned long r4, unsigned long r5, if (__copy_from_user(&set, &uc->uc_sigmask, sizeof(set))) goto badframe; set_current_blocked(&set); + #ifdef CONFIG_PPC_TRANSACTIONAL_MEM + /* + * If there is a transactional/suspended state then throw it away. + * The purpose of a sigreturn is to destroy all traces of the + * signal frame, this includes any transactional state created + * within in. + * The cause is not important as there will never be a + * recheckpoint so it's not user visible. + */ + if (MSR_TM_ACTIVE(mfmsr())) + tm_reclaim_current(0); + if (__get_user(msr, &uc->uc_mcontext.gp_regs[PT_MSR])) goto badframe; if (MSR_TM_ACTIVE(msr)) {
Userspace can begin and suspend a transaction within the signal handler which means they might enter sys_rt_sigreturn() with the processor in suspended state. sys_rt_sigreturn() wants to restore process context (which may have been in a transaction before signal delivery). To do this it must restore TM SPRS. To achieve this, any transaction initiated within the signal frame must be discarded in order to be able to restore TM SPRs as TM SPRs can only be manipulated non-transactionally.. From the PowerPC ISA: TM Bad Thing Exception [Category: Transactional Memory] An attempt is made to execute a mtspr targeting a TM register in other than Non-transactional state. Not doing so results in a TM Bad Thing: [12045.221359] Kernel BUG at c000000000050a40 [verbose debug info unavailable] [12045.221470] Unexpected TM Bad Thing exception at c000000000050a40 (msr 0x201033) [12045.221540] Oops: Unrecoverable exception, sig: 6 [#1] [12045.221586] SMP NR_CPUS=2048 NUMA PowerNV [12045.221634] Modules linked in: xt_CHECKSUM iptable_mangle ipt_MASQUERADE nf_nat_masquerade_ipv4 iptable_nat nf_nat_ipv4 nf_nat nf_conntrack_ipv4 nf_defrag_ipv4 xt_conntrack nf_conntrack ipt_REJECT nf_reject_ipv4 xt_tcpudp bridge stp llc ebtable_filter ebtables ip6table_filter ip6_tables iptable_filter ip_tables x_tables kvm_hv kvm uio_pdrv_genirq ipmi_powernv uio powernv_rng ipmi_msghandler autofs4 ses enclosure scsi_transport_sas bnx2x ipr mdio libcrc32c [12045.222167] CPU: 68 PID: 6178 Comm: sigreturnpanic Not tainted 4.7.0 #34 [12045.222224] task: c0000000fce38600 ti: c0000000fceb4000 task.ti: c0000000fceb4000 [12045.222293] NIP: c000000000050a40 LR: c0000000000163bc CTR: 0000000000000000 [12045.222361] REGS: c0000000fceb7ac0 TRAP: 0700 Not tainted (4.7.0) [12045.222418] MSR: 9000000300201033 <SF,HV,ME,IR,DR,RI,LE,TM[SE]> CR: 28444280 XER: 20000000 [12045.222625] CFAR: c0000000000163b8 SOFTE: 0 PACATMSCRATCH: 900000014280f033 GPR00: 01100000b8000001 c0000000fceb7d40 c00000000139c100 c0000000fce390d0 GPR04: 900000034280f033 0000000000000000 0000000000000000 0000000000000000 GPR08: 0000000000000000 b000000000001033 0000000000000001 0000000000000000 GPR12: 0000000000000000 c000000002926400 0000000000000000 0000000000000000 GPR16: 0000000000000000 0000000000000000 0000000000000000 0000000000000000 GPR20: 0000000000000000 0000000000000000 0000000000000000 0000000000000000 GPR24: 0000000000000000 00003ffff98cadd0 00003ffff98cb470 0000000000000000 GPR28: 900000034280f033 c0000000fceb7ea0 0000000000000001 c0000000fce390d0 [12045.223535] NIP [c000000000050a40] tm_restore_sprs+0xc/0x1c [12045.223584] LR [c0000000000163bc] tm_recheckpoint+0x5c/0xa0 [12045.223630] Call Trace: [12045.223655] [c0000000fceb7d80] [c000000000026e74] sys_rt_sigreturn+0x494/0x6c0 [12045.223738] [c0000000fceb7e30] [c0000000000092e0] system_call+0x38/0x108 [12045.223806] Instruction dump: [12045.223841] 7c800164 4e800020 7c0022a6 f80304a8 7c0222a6 f80304b0 7c0122a6 f80304b8 [12045.223955] 4e800020 e80304a8 7c0023a6 e80304b0 <7c0223a6> e80304b8 7c0123a6 4e800020 [12045.224074] ---[ end trace cb8002ee240bae76 ]--- It isn't clear exactly if there is really a use case for userspace returning with a suspended transaction, however, doing so doesn't (on its own) constitute a bad frame. As such, this patch simply discards the transactional state of the context calling the sigreturn and continues. Reported-by: Laurent Dufour <ldufour@linux.vnet.ibm.com> Signed-off-by: Cyril Bur <cyrilbur@gmail.com> --- V2: Move the code down into the #ifdef CONFIG_PPC_TRANSACTIONAL_MEM (32 and 64 bit) Add a small amount of text to Documentation Adjust the commit message for clarity Documentation/powerpc/transactional_memory.txt | 2 ++ arch/powerpc/kernel/signal_32.c | 12 ++++++++++++ arch/powerpc/kernel/signal_64.c | 12 ++++++++++++ 3 files changed, 26 insertions(+)