[Bug 294039] databases/postgresql14-server: jemalloc crashes triggered by autovacuum

https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=294039

Mark Johnston <markj@FreeBSD.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|New                         |Open

--- Comment #9 from Mark Johnston <markj@FreeBSD.org> ---
I see a case where we can restart the fault handler without resetting
m_needs_zeroing: if vm_fault_object() encounters a busy page in a backing
object, it will call vm_fault_busy_sleep(), which resets fault state using a
custom routine.  If a page allocation had previously set m_needs_zeroing =
false, and the newly allocated page was reclaimed while restarting the fault
handler, then we'll allocate a new page using the stale m_needs_zeroing value.

A minimal patch to fix this is:

diff --git a/sys/vm/vm_fault.c b/sys/vm/vm_fault.c
index 64580c34c0a0..cf20304706ad 100644
--- a/sys/vm/vm_fault.c
+++ b/sys/vm/vm_fault.c
@@ -1436,6 +1436,7 @@ vm_fault_busy_sleep(struct faultstate *fs)
                VM_OBJECT_UNLOCK(fs->object);
        VM_CNT_INC(v_intrans);
        vm_object_deallocate(fs->first_object);
+       fs->m_needs_zeroing = true;
 }

Peter, I wonder if you could test this with the original patch re-applied?

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