From 0393f542d72c6182271c392d9a83d0fc775113c7 Mon Sep 17 00:00:00 2001 From: Heikki Linnakangas Date: Mon, 29 Jul 2024 18:17:33 +0300 Subject: [PATCH] Fix double-release of spinlock Commit 9d9b9d46f3 added spinlocks to protect the fields in ProcSignal flags, but in EmitProcSignalBarrier(), the spinlock was released twice. With most spinlock implementations, releasing a lock that's not held is not easy to notice, because most of the time it does nothing, but if the spinlock was concurrently acquired by another process, it could lead to more serious issues. Fortunately, with the --disable-spinlocks emulation implementation, it caused more visible failures. In the passing, fix a type in comment and add an assertion that the procNumber passed to SendProcSignal looks valid. Discussion: https://www.postgresql.org/message-id/b8ce284c-18a2-4a79-afd3-1991a2e7d246@iki.fi --- src/backend/storage/ipc/procsignal.c | 6 ++++-- 1 file changed, 4 insertions(+), 2 deletions(-) diff --git a/src/backend/storage/ipc/procsignal.c b/src/backend/storage/ipc/procsignal.c index 038aeca6151..87027f27eb7 100644 --- a/src/backend/storage/ipc/procsignal.c +++ b/src/backend/storage/ipc/procsignal.c @@ -284,6 +284,7 @@ SendProcSignal(pid_t pid, ProcSignalReason reason, ProcNumber procNumber) if (procNumber != INVALID_PROC_NUMBER) { + Assert(procNumber < NumProcSignalSlots); slot = &ProcSignal->psh_slot[procNumber]; SpinLockAcquire(&slot->pss_mutex); @@ -300,7 +301,7 @@ SendProcSignal(pid_t pid, ProcSignalReason reason, ProcNumber procNumber) else { /* - * Pronumber not provided, so search the array using pid. We search + * procNumber not provided, so search the array using pid. We search * the array back to front so as to reduce search overhead. Passing * INVALID_PROC_NUMBER means that the target is most likely an * auxiliary process, which will have a slot near the end of the @@ -404,7 +405,8 @@ EmitProcSignalBarrier(ProcSignalBarrierType type) SpinLockRelease(&slot->pss_mutex); kill(pid, SIGUSR1); } - SpinLockRelease(&slot->pss_mutex); + else + SpinLockRelease(&slot->pss_mutex); } } -- 2.39.5