aio: table lookup: verify ctx pointer

Another shortcoming of the table lookup patch was revealed where the pointer
was not being tested before being dereferenced.  Verify this to avoid the
NULL pointer dereference.

Signed-off-by: Benjamin LaHaise <bcrl@kvack.org>

diff --git a/fs/aio.c b/fs/aio.c
index 3bc068c1cb9cbfaec0e33dfe5efd26ec361e2c93..c3f005dc2d55211ea055ad8ccc9715a76eff24ac 100644 (file)
--- a/fs/aio.c
+++ b/fs/aio.c
@@ -812,7 +812,7 @@ static struct kioctx *lookup_ioctx(unsigned long ctx_id)
                goto out;
 
        ctx = table->table[id];
-       if (ctx->user_id == ctx_id) {
+       if (ctx && ctx->user_id == ctx_id) {
                percpu_ref_get(&ctx->users);
                ret = ctx;
        }