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authorNicholas Piggin <npiggin@gmail.com>2023-02-06 14:22:40 +1000
committerMichael Ellerman <mpe@ellerman.id.au>2023-02-07 10:13:33 +1100
commit2ea31e2e62bbc4d11c411eeb36f1b02841dbcab1 (patch)
tree2670e8f5cbcc495e79be1835f8292c0bb573d470
parent97e45d469eb180a7bd2809e4e079331552c73e42 (diff)
powerpc/64s/interrupt: Fix interrupt exit race with security mitigation switch
The RFI and STF security mitigation options can flip the interrupt_exit_not_reentrant static branch condition concurrently with the interrupt exit code which tests that branch. Interrupt exit tests this condition to set MSR[EE|RI] for exit, then again in the case a soft-masked interrupt is found pending, to recover the MSR so the interrupt can be replayed before attempting to exit again. If the condition changes between these two tests, the MSR and irq soft-mask state will become corrupted, leading to warnings and possible crashes. For example, if the branch is initially true then false, MSR[EE] will be 0 but PACA_IRQ_HARD_DIS clear and EE may not get enabled, leading to warnings in irq_64.c. Fixes: 13799748b957 ("powerpc/64: use interrupt restart table to speed up return from interrupt") Cc: stable@vger.kernel.org # v5.14+ Reported-by: Sachin Sant <sachinp@linux.ibm.com> Tested-by: Sachin Sant <sachinp@linux.ibm.com> Signed-off-by: Nicholas Piggin <npiggin@gmail.com> Signed-off-by: Michael Ellerman <mpe@ellerman.id.au> Link: https://lore.kernel.org/r/20230206042240.92103-1-npiggin@gmail.com
-rw-r--r--arch/powerpc/kernel/interrupt.c6
1 files changed, 4 insertions, 2 deletions
diff --git a/arch/powerpc/kernel/interrupt.c b/arch/powerpc/kernel/interrupt.c
index fc6631a80527..0ec1581619db 100644
--- a/arch/powerpc/kernel/interrupt.c
+++ b/arch/powerpc/kernel/interrupt.c
@@ -50,16 +50,18 @@ static inline bool exit_must_hard_disable(void)
*/
static notrace __always_inline bool prep_irq_for_enabled_exit(bool restartable)
{
+ bool must_hard_disable = (exit_must_hard_disable() || !restartable);
+
/* This must be done with RI=1 because tracing may touch vmaps */
trace_hardirqs_on();
- if (exit_must_hard_disable() || !restartable)
+ if (must_hard_disable)
__hard_EE_RI_disable();
#ifdef CONFIG_PPC64
/* This pattern matches prep_irq_for_idle */
if (unlikely(lazy_irq_pending_nocheck())) {
- if (exit_must_hard_disable() || !restartable) {
+ if (must_hard_disable) {
local_paca->irq_happened |= PACA_IRQ_HARD_DIS;
__hard_RI_enable();
}