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-rw-r--r--arch/powerpc/kernel/signal_64.c13
1 files changed, 12 insertions, 1 deletions
diff --git a/arch/powerpc/kernel/signal_64.c b/arch/powerpc/kernel/signal_64.c
index c83c115858c1..b2c002993d78 100644
--- a/arch/powerpc/kernel/signal_64.c
+++ b/arch/powerpc/kernel/signal_64.c
@@ -452,9 +452,20 @@ static long restore_tm_sigcontexts(struct task_struct *tsk,
if (MSR_TM_RESV(msr))
return -EINVAL;
- /* pull in MSR TM from user context */
+ /* pull in MSR TS bits from user context */
regs->msr = (regs->msr & ~MSR_TS_MASK) | (msr & MSR_TS_MASK);
+ /*
+ * Ensure that TM is enabled in regs->msr before we leave the signal
+ * handler. It could be the case that (a) user disabled the TM bit
+ * through the manipulation of the MSR bits in uc_mcontext or (b) the
+ * TM bit was disabled because a sufficient number of context switches
+ * happened whilst in the signal handler and load_tm overflowed,
+ * disabling the TM bit. In either case we can end up with an illegal
+ * TM state leading to a TM Bad Thing when we return to userspace.
+ */
+ regs->msr |= MSR_TM;
+
/* pull in MSR LE from user context */
regs->msr = (regs->msr & ~MSR_LE) | (msr & MSR_LE);