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

[Greg KH]

On Mon, Mar 23, 2026 at 07:37:24AM -0600, Jens Axboe wrote:
> 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!

Now done, thanks.

greg k-h