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 @@ -332,6 +332,9 @@ 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;
@@ -345,6 +348,7 @@ static int aio_ring_mremap(struct vm_are } }
+out_unlock: rcu_read_unlock(); spin_unlock(&mm->ioctx_lock); return res;