From 326941b22806cbf2df1fbfe902b7908b368cce42 Mon Sep 17 00:00:00 2001 From: Longxuan Yu Date: Sun, 12 Apr 2026 16:38:20 +0800 Subject: [PATCH] io_uring/poll: fix signed comparison in io_poll_get_ownership() io_poll_get_ownership() uses a signed comparison to check whether poll_refs has reached the threshold for the slowpath: if (unlikely(atomic_read(&req->poll_refs) >= IO_POLL_REF_BIAS)) atomic_read() returns int (signed). When IO_POLL_CANCEL_FLAG (BIT(31)) is set in poll_refs, the value becomes negative in signed arithmetic, so the >= 128 comparison always evaluates to false and the slowpath is never taken. Fix this by casting the atomic_read() result to unsigned int before the comparison, so that the cancel flag is treated as a large positive value and correctly triggers the slowpath. Fixes: a26a35e9019f ("io_uring: make poll refs more robust") Cc: stable@vger.kernel.org Reported-by: Yifan Wu Reported-by: Juefei Pu Co-developed-by: Yuan Tan Signed-off-by: Yuan Tan Suggested-by: Xin Liu Tested-by: Zhengchuan Liang Signed-off-by: Longxuan Yu Signed-off-by: Ren Wei Reviewed-by: Pavel Begunkov Link: https://patch.msgid.link/3a3508b08bcd7f1bc3beff848ae6e1d73d355043.1775965597.git.ylong030@ucr.edu Signed-off-by: Jens Axboe --- io_uring/poll.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/io_uring/poll.c b/io_uring/poll.c index 74eef7884159..6834e2db937e 100644 --- a/io_uring/poll.c +++ b/io_uring/poll.c @@ -93,7 +93,7 @@ static bool io_poll_get_ownership_slowpath(struct io_kiocb *req) */ static inline bool io_poll_get_ownership(struct io_kiocb *req) { - if (unlikely(atomic_read(&req->poll_refs) >= IO_POLL_REF_BIAS)) + if (unlikely((unsigned int)atomic_read(&req->poll_refs) >= IO_POLL_REF_BIAS)) return io_poll_get_ownership_slowpath(req); return !(atomic_fetch_inc(&req->poll_refs) & IO_POLL_REF_MASK); }