aio: restore locking of ioctx list on removal

Commit 36f5588905c10a8c4568a210d601fe8c3c27e0f0
"aio: refcounting cleanup" resulted in ioctx_lock not being held
during ctx removal, leaving the list susceptible to corruptions.

In mainline kernel the issue went away as a side effect of
db446a08c23d5475e6b08c87acca79ebb20f283c "aio: convert the ioctx list to
table lookup v3".

Fix the problem by restoring appropriate locking.

Signed-off-by: Mateusz Guzik <mguzik@redhat.com>
Reported-by: Eryu Guan <eguan@redhat.com>
Cc: Jeff Moyer <jmoyer@redhat.com>
Cc: Kent Overstreet <kmo@daterainc.com>
Acked-by: Benjamin LaHaise <bcrl@kvack.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

1 files changed, 6 insertions, 4 deletions

diff --git a/fs/aio.c b/fs/aio.c
index 2bbcacf74d0c..ebd06fd0de89 100644
--- a/fs/aio.c
+++ b/fs/aio.c
@@ -423,10 +423,12 @@ static void kill_ioctx_rcu(struct rcu_head *head)
  *      when the processes owning a context have all exited to encourage
  *      the rapid destruction of the kioctx.
  */
-static void kill_ioctx(struct kioctx *ctx)
+static void kill_ioctx(struct mm_struct *mm, struct kioctx *ctx)
 {
         if (!atomic_xchg(&ctx->dead, 1)) {
+                spin_lock(&mm->ioctx_lock);
                 hlist_del_rcu(&ctx->list);
+                spin_unlock(&mm->ioctx_lock);
 
                 /*
                  * It'd be more correct to do this in free_ioctx(), after all
@@ -494,7 +496,7 @@ void exit_aio(struct mm_struct *mm)
                  */
                 ctx->mmap_size = 0;
 
-                kill_ioctx(ctx);
+                kill_ioctx(mm, ctx);
         }
 }
 
@@ -852,7 +854,7 @@ SYSCALL_DEFINE2(io_setup, unsigned, nr_events, aio_context_t __user *, ctxp)
         if (!IS_ERR(ioctx)) {
                 ret = put_user(ioctx->user_id, ctxp);
                 if (ret)
-                        kill_ioctx(ioctx);
+                        kill_ioctx(current->mm, ioctx);
                 put_ioctx(ioctx);
         }
 
@@ -870,7 +872,7 @@ SYSCALL_DEFINE1(io_destroy, aio_context_t, ctx)
 {
         struct kioctx *ioctx = lookup_ioctx(ctx);
         if (likely(NULL != ioctx)) {
-                kill_ioctx(ioctx);
+                kill_ioctx(current->mm, ioctx);
                 put_ioctx(ioctx);
                 return 0;
         }