Re: [PATCH 5.15.y] io_uring/tctx: work around xa_store() allocation error issue

[Jens Axboe]

On 3/23/26 2:19 AM, Robert Garcia wrote:
> From: Jens Axboe <axboe@xxxxxxxxx>
> 
> [ Upstream commit 7eb75ce7527129d7f1fee6951566af409a37a1c4 ]
> 
> syzbot triggered the following WARN_ON:
> 
> WARNING: CPU: 0 PID: 16 at io_uring/tctx.c:51 __io_uring_free+0xfa/0x140 io_uring/tctx.c:51
> 
> which is the
> 
> WARN_ON_ONCE(!xa_empty(&tctx->xa));
> 
> sanity check in __io_uring_free() when a io_uring_task is going through
> its final put. The syzbot test case includes injecting memory allocation
> failures, and it very much looks like xa_store() can fail one of its
> memory allocations and end up with ->head being non-NULL even though no
> entries exist in the xarray.
> 
> Until this issue gets sorted out, work around it by attempting to
> iterate entries in our xarray, and WARN_ON_ONCE() if one is found.
> 
> Reported-by: syzbot+cc36d44ec9f368e443d3@xxxxxxxxxxxxxxxxxxxxxxxxx
> Link: https://lore.kernel.org/io-uring/673c1643.050a0220.87769.0066.GAE@xxxxxxxxxx/
> Signed-off-by: Jens Axboe <axboe@xxxxxxxxx>
> [ Modify the function in io_uring.c because it's located here in v5.15. ]
> Signed-off-by: Robert Garcia <rob_garcia@xxxxxxx>

I'm find adding this to 5.15 stable. However, this also need to go to
5.10-stable then as the io_uring bases are identical. Greg, when you
queue this up, please add to both. Thanks!

-- 
Jens Axboe