powerpc/tm: Block signal return setting invalid MSR state
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: 2b0a576d15e0 ("powerpc: Add new transactional memory state to the signal context")
Cc: stable@vger.kernel.org # v3.9+
Signed-off-by: Michael Neuling <mikey@neuling.org>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
diff --git a/arch/powerpc/kernel/signal_32.c b/arch/powerpc/kernel/signal_32.c
index 0dbee46..ef7c24e 100644
--- a/arch/powerpc/kernel/signal_32.c
+++ b/arch/powerpc/kernel/signal_32.c
@@ -875,6 +875,15 @@
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.
@@ -884,11 +893,6 @@
current->thread.tm_texasr |= TEXASR_FS;
/* This loads the checkpointed FP/VEC state, if used */
tm_recheckpoint(¤t->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) {