[PATCH][next] io_uring: fix missing error return when percpu_ref_init fails

[PATCH][next] io_uring: fix missing error return when percpu_ref_init fails

[Colin King]

From: Colin Ian King <colin.king@canonical.com>

Currently when the call to percpu_ref_init fails ctx->file_data is
set to null and because there is a missing return statement the
following statement dereferences this null pointer causing an oops.
Fix this by adding the missing -ENOMEM return to avoid the oops.

Addresses-Coverity: ("Explicit null dereference")
Fixes: cbb537634780 ("io_uring: avoid ring quiesce for fixed file set unregister and update")
Signed-off-by: Colin Ian King <colin.king@canonical.com>
---
 fs/io_uring.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/fs/io_uring.c b/fs/io_uring.c
index c756b8fc44c6..1d31294f5914 100644
--- a/fs/io_uring.c
+++ b/fs/io_uring.c
@@ -4937,6 +4937,7 @@ static int io_sqe_files_register(struct io_ring_ctx *ctx, void __user *arg,
 		kfree(ctx->file_data->table);
 		kfree(ctx->file_data);
 		ctx->file_data = NULL;
+		return -ENOMEM;
 	}
 	ctx->file_data->put_llist.first = NULL;
 	INIT_WORK(&ctx->file_data->ref_work, io_ring_file_ref_switch);
-- 
2.24.0

Re: [PATCH][next] io_uring: fix missing error return when percpu_ref_init fails

[Jens Axboe]

On 12/20/19 4:33 PM, Colin King wrote:
> From: Colin Ian King <colin.king@canonical.com>
> 
> Currently when the call to percpu_ref_init fails ctx->file_data is
> set to null and because there is a missing return statement the
> following statement dereferences this null pointer causing an oops.
> Fix this by adding the missing -ENOMEM return to avoid the oops.

Nice, thanks! I'm guessing I didn't have the necessary magic debug
options to allow failure injection for failing.


-- 
Jens Axboe

Re: [PATCH][next] io_uring: fix missing error return when percpu_ref_init fails

[Colin Ian King]

On 20/12/2019 23:48, Jens Axboe wrote:
> On 12/20/19 4:33 PM, Colin King wrote:
>> From: Colin Ian King <colin.king@canonical.com>
>>
>> Currently when the call to percpu_ref_init fails ctx->file_data is
>> set to null and because there is a missing return statement the
>> following statement dereferences this null pointer causing an oops.
>> Fix this by adding the missing -ENOMEM return to avoid the oops.
> 
> Nice, thanks! I'm guessing I didn't have the necessary magic debug
> options to allow failure injection for failing.

Fortunately we have Coverity to the rescue :-)

Colin

Re: [PATCH][next] io_uring: fix missing error return when percpu_ref_init fails

[Jens Axboe]

On 12/20/19 4:49 PM, Colin Ian King wrote:
> On 20/12/2019 23:48, Jens Axboe wrote:
>> On 12/20/19 4:33 PM, Colin King wrote:
>>> From: Colin Ian King <colin.king@canonical.com>
>>>
>>> Currently when the call to percpu_ref_init fails ctx->file_data is
>>> set to null and because there is a missing return statement the
>>> following statement dereferences this null pointer causing an oops.
>>> Fix this by adding the missing -ENOMEM return to avoid the oops.
>>
>> Nice, thanks! I'm guessing I didn't have the necessary magic debug
>> options to allow failure injection for failing.
> 
> Fortunately we have Coverity to the rescue :-)

Indeed!

-- 
Jens Axboe