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powerpc/tm: Block signal return setting invalid MSR state

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commit d2b9d2a5ad5ef04ff978c9923d19730cb05efd55 upstream.

Currently we allow both the MSR T and S bits to be set by userspace on
a signal return.  Unfortunately this is a reserved configuration and
will cause a TM Bad Thing exception if attempted (via rfid).

This patch checks for this case in both the 32 and 64 bit signals
code.  If both T and S are set, we mark the context as invalid.

Found using a syscall fuzzer.

Fixes: 2b0a576d15 ("powerpc: Add new transactional memory state to the signal context")
Signed-off-by: Michael Neuling <mikey@neuling.org>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Michael Neuling 2015-11-19 15:44:44 +11:00 committed by Greg Kroah-Hartman
parent c496409d87
commit 5d64942934
3 changed files with 14 additions and 5 deletions
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1
arch/powerpc/include/asm/reg.h
View file

@ -108,6 +108,7 @@
#define MSR_TS_T __MASK(MSR_TS_T_LG) /* Transaction Transactional */
#define MSR_TS_MASK (MSR_TS_T | MSR_TS_S) /* Transaction State bits */
#define MSR_TM_ACTIVE(x) (((x) & MSR_TS_MASK) != 0) /* Transaction active? */
#define MSR_TM_RESV(x) (((x) & MSR_TS_MASK) == MSR_TS_MASK) /* Reserved */
#define MSR_TM_TRANSACTIONAL(x) (((x) & MSR_TS_MASK) == MSR_TS_T)
#define MSR_TM_SUSPENDED(x) (((x) & MSR_TS_MASK) == MSR_TS_S)

14
arch/powerpc/kernel/signal_32.c
View file

@ -858,6 +858,15 @@ static long restore_tm_user_regs(struct pt_regs *regs,
return 1;
#endif /* CONFIG_SPE */
/* Get the top half of the MSR from the user context */
if (__get_user(msr_hi, &tm_sr->mc_gregs[PT_MSR]))
return 1;
msr_hi <<= 32;
/* If TM bits are set to the reserved value, it's an invalid context */
if (MSR_TM_RESV(msr_hi))
return 1;
/* Pull in the MSR TM bits from the user context */
regs->msr = (regs->msr & ~MSR_TS_MASK) | (msr_hi & MSR_TS_MASK);
/* Now, recheckpoint. This loads up all of the checkpointed (older)
* registers, including FP and V[S]Rs. After recheckpointing, the
* transactional versions should be loaded.
@ -867,11 +876,6 @@ static long restore_tm_user_regs(struct pt_regs *regs,
current->thread.tm_texasr |= TEXASR_FS;
/* This loads the checkpointed FP/VEC state, if used */
tm_recheckpoint(&current->thread, msr);
/* Get the top half of the MSR */
if (__get_user(msr_hi, &tm_sr->mc_gregs[PT_MSR]))
return 1;
/* Pull in MSR TM from user context */
regs->msr = (regs->msr & ~MSR_TS_MASK) | ((msr_hi<<32) & MSR_TS_MASK);
/* This loads the speculative FP/VEC state, if used */
if (msr & MSR_FP) {

4
arch/powerpc/kernel/signal_64.c
View file

@ -416,6 +416,10 @@ static long restore_tm_sigcontexts(struct pt_regs *regs,
/* get MSR separately, transfer the LE bit if doing signal return */
err |= __get_user(msr, &sc->gp_regs[PT_MSR]);
/* Don't allow reserved mode. */
if (MSR_TM_RESV(msr))
return -EINVAL;
/* pull in MSR TM from user context */
regs->msr = (regs->msr & ~MSR_TS_MASK) | (msr & MSR_TS_MASK);