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> Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx> --- io_uring/tctx.c | 13 ++++++++++++- 1 file changed, 12 insertions(+), 1 deletion(-) diff --git a/io_uring/tctx.c b/io_uring/tctx.c index 4324b1cf1f6af..51b05fda8e455 100644 --- a/io_uring/tctx.c +++ b/io_uring/tctx.c @@ -47,8 +47,19 @@ static struct io_wq *io_init_wq_offload(struct io_ring_ctx *ctx, void __io_uring_free(struct task_struct *tsk) { struct io_uring_task *tctx = tsk->io_uring; + struct io_tctx_node *node; + unsigned long index; - WARN_ON_ONCE(!xa_empty(&tctx->xa)); + /* + * Fault injection forcing allocation errors in the xa_store() path + * can lead to xa_empty() returning false, even though no actual + * node is stored in the xarray. Until that gets sorted out, attempt + * an iteration here and warn if any entries are found. + */ + xa_for_each(&tctx->xa, index, node) { + WARN_ON_ONCE(1); + break; + } WARN_ON_ONCE(tctx->io_wq); WARN_ON_ONCE(tctx->cached_refs); -- 2.43.0
