* [PATCH AUTOSEL 6.1 4/4] io_uring/tctx: work around xa_store() allocation error issue
[not found] <[email protected]>
@ 2024-12-04 22:24 ` Sasha Levin
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From: Sasha Levin @ 2024-12-04 22:24 UTC (permalink / raw)
To: linux-kernel, stable
Cc: Jens Axboe, syzbot+cc36d44ec9f368e443d3, Sasha Levin,
asml.silence, io-uring
From: Jens Axboe <[email protected]>
[ 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: [email protected]
Link: https://lore.kernel.org/io-uring/[email protected]/
Signed-off-by: Jens Axboe <[email protected]>
Signed-off-by: Sasha Levin <[email protected]>
---
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
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