[PATCH 3/3] powerpc/64: Only warn for kuap locked when KCSAN not present

Rohan McLure rmclure at linux.ibm.com
Mon Nov 27 16:46:47 AEDT 2023

Arbitrary instrumented locations, including syscall handlers, can call
arch_local_irq_restore() transitively when KCSAN is enabled, and in turn
also replay_soft_interrupts_irqrestore(). The precondition on entry to
this routine that is checked is that KUAP is enabled (user access
prohibited). Failure to meet this condition only triggers a warning
however, and afterwards KUAP is enabled anyway. That is, KUAP being
disabled on entry is in fact permissable, but not possible on an
uninstrumented kernel.

Disable this assertion only when KCSAN is enabled.

Suggested-by: Nicholas Piggin <npiggin at gmail.com>
Signed-off-by: Rohan McLure <rmclure at linux.ibm.com>
 arch/powerpc/kernel/irq_64.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/arch/powerpc/kernel/irq_64.c b/arch/powerpc/kernel/irq_64.c
index 938e66829eae..1b7e8ebb052a 100644
--- a/arch/powerpc/kernel/irq_64.c
+++ b/arch/powerpc/kernel/irq_64.c
@@ -189,7 +189,8 @@ static inline __no_kcsan void replay_soft_interrupts_irqrestore(void)
 	 * and re-locking AMR but we shouldn't get here in the first place,
 	 * hence the warning.
-	kuap_assert_locked();
+		kuap_assert_locked();
 	if (kuap_state != AMR_KUAP_BLOCKED)

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