--- /dev/null
+From 81e9d6f8647650a7bead74c5f926e29970e834d1 Mon Sep 17 00:00:00 2001
+From: Seth Jenkins <sethjenkins@google.com>
+Date: Tue, 31 Jan 2023 12:25:55 -0500
+Subject: aio: fix mremap after fork null-deref
+
+From: Seth Jenkins <sethjenkins@google.com>
+
+commit 81e9d6f8647650a7bead74c5f926e29970e834d1 upstream.
+
+Commit e4a0d3e720e7 ("aio: Make it possible to remap aio ring") introduced
+a null-deref if mremap is called on an old aio mapping after fork as
+mm->ioctx_table will be set to NULL.
+
+[jmoyer@redhat.com: fix 80 column issue]
+Link: https://lkml.kernel.org/r/x49sffq4nvg.fsf@segfault.boston.devel.redhat.com
+Fixes: e4a0d3e720e7 ("aio: Make it possible to remap aio ring")
+Signed-off-by: Seth Jenkins <sethjenkins@google.com>
+Signed-off-by: Jeff Moyer <jmoyer@redhat.com>
+Cc: Alexander Viro <viro@zeniv.linux.org.uk>
+Cc: Benjamin LaHaise <bcrl@kvack.org>
+Cc: Jann Horn <jannh@google.com>
+Cc: Pavel Emelyanov <xemul@parallels.com>
+Cc: <stable@vger.kernel.org>
+Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
+Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
+---
+ fs/aio.c | 4 ++++
+ 1 file changed, 4 insertions(+)
+
+--- a/fs/aio.c
++++ b/fs/aio.c
+@@ -328,6 +328,9 @@ static int aio_ring_mremap(struct vm_are
+ spin_lock(&mm->ioctx_lock);
+ rcu_read_lock();
+ table = rcu_dereference(mm->ioctx_table);
++ if (!table)
++ goto out_unlock;
++
+ for (i = 0; i < table->nr; i++) {
+ struct kioctx *ctx;
+
+@@ -341,6 +344,7 @@ static int aio_ring_mremap(struct vm_are
+ }
+ }
+
++out_unlock:
+ rcu_read_unlock();
+ spin_unlock(&mm->ioctx_lock);
+ return res;