From 24dd34af1435a2a97e8b67d82328e45d0ac51413 Mon Sep 17 00:00:00 2001 From: Thomas Munro Date: Sat, 1 Feb 2020 14:29:13 +1300 Subject: [PATCH] Fix memory leak on DSM slot exhaustion. If we attempt to create a DSM segment when no slots are available, we should return the memory to the operating system. Previously we did that if the DSM_CREATE_NULL_IF_MAXSEGMENTS flag was passed in, but we didn't do it if an error was raised. Repair. Back-patch to 9.4, where DSM segments arrived. Author: Thomas Munro Reviewed-by: Robert Haas Reported-by: Julian Backes Discussion: https://postgr.es/m/CA%2BhUKGKAAoEw-R4om0d2YM4eqT1eGEi6%3DQot-3ceDR-SLiWVDw%40mail.gmail.com --- src/backend/storage/ipc/dsm.c | 17 ++++++++--------- 1 file changed, 8 insertions(+), 9 deletions(-) diff --git a/src/backend/storage/ipc/dsm.c b/src/backend/storage/ipc/dsm.c index 142293fd2c..9bf16de940 100644 --- a/src/backend/storage/ipc/dsm.c +++ b/src/backend/storage/ipc/dsm.c @@ -484,17 +484,16 @@ dsm_create(Size size, int flags) /* Verify that we can support an additional mapping. */ if (nitems >= dsm_control->maxitems) { + LWLockRelease(DynamicSharedMemoryControlLock); + dsm_impl_op(DSM_OP_DESTROY, seg->handle, 0, &seg->impl_private, + &seg->mapped_address, &seg->mapped_size, WARNING); + if (seg->resowner != NULL) + ResourceOwnerForgetDSM(seg->resowner, seg); + dlist_delete(&seg->node); + pfree(seg); + if ((flags & DSM_CREATE_NULL_IF_MAXSEGMENTS) != 0) - { - LWLockRelease(DynamicSharedMemoryControlLock); - dsm_impl_op(DSM_OP_DESTROY, seg->handle, 0, &seg->impl_private, - &seg->mapped_address, &seg->mapped_size, WARNING); - if (seg->resowner != NULL) - ResourceOwnerForgetDSM(seg->resowner, seg); - dlist_delete(&seg->node); - pfree(seg); return NULL; - } ereport(ERROR, (errcode(ERRCODE_INSUFFICIENT_RESOURCES), errmsg("too many dynamic shared memory segments")));