aio: table lookup: verify ctx pointer

bcrl · bcrl · commit f30d704fe124 · 2013-08-07T18:23:48.000-04:00
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 &lt;bcrl@kvack.org&gt;
diff --git 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;
 	}

Original file line number	Diff line number	Diff line change
`@@ -812,7 +812,7 @@ static struct kioctx *lookup_ioctx(unsigned long ctx_id)`
`812`	`812`	`goto out;`
`813`	`813`
`814`	`814`	`ctx = table->table[id];`
`815`		`- if (ctx->user_id == ctx_id) {`
	`815`	`+ if (ctx && ctx->user_id == ctx_id) {`
`816`	`816`	`percpu_ref_get(&ctx->users);`
`817`	`817`	`ret = ctx;`
`818`	`818`	`}`