6.9-stable review patch. If anyone has any objections, please let me know.
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From: Pavel Begunkov asml.silence@gmail.com
commit f4a1254f2a076afb0edd473589bf40f9b4d36b41 upstream.
Only the current owner of a request is allowed to write into req->flags. Hence, the cancellation path should never touch it. Add a new field instead of the flag, move it into the 3rd cache line because it should always be initialised. poll_refs can move further as polling is an involved process anyway.
It's a minimal patch, in the future we can and should find a better place for it and remove now unused REQ_F_CANCEL_SEQ.
Fixes: 521223d7c229f ("io_uring/cancel: don't default to setting req->work.cancel_seq") Cc: stable@vger.kernel.org Reported-by: Li Shi sl1589472800@gmail.com Signed-off-by: Pavel Begunkov asml.silence@gmail.com Link: https://lore.kernel.org/r/6827b129f8f0ad76fa9d1f0a773de938b240ffab.171832343... Signed-off-by: Jens Axboe axboe@kernel.dk Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- include/linux/io_uring_types.h | 3 ++- io_uring/cancel.h | 4 ++-- io_uring/io_uring.c | 1 + 3 files changed, 5 insertions(+), 3 deletions(-)
--- a/include/linux/io_uring_types.h +++ b/include/linux/io_uring_types.h @@ -653,7 +653,7 @@ struct io_kiocb { struct io_rsrc_node *rsrc_node;
atomic_t refs; - atomic_t poll_refs; + bool cancel_seq_set; struct io_task_work io_task_work; /* for polled requests, i.e. IORING_OP_POLL_ADD and async armed poll */ struct hlist_node hash_node; @@ -662,6 +662,7 @@ struct io_kiocb { /* opcode allocated if it needs to store data for async defer */ void *async_data; /* linked requests, IFF REQ_F_HARDLINK or REQ_F_LINK are set */ + atomic_t poll_refs; struct io_kiocb *link; /* custom credentials, valid IFF REQ_F_CREDS is set */ const struct cred *creds; --- a/io_uring/cancel.h +++ b/io_uring/cancel.h @@ -27,10 +27,10 @@ bool io_cancel_req_match(struct io_kiocb
static inline bool io_cancel_match_sequence(struct io_kiocb *req, int sequence) { - if ((req->flags & REQ_F_CANCEL_SEQ) && sequence == req->work.cancel_seq) + if (req->cancel_seq_set && sequence == req->work.cancel_seq) return true;
- req->flags |= REQ_F_CANCEL_SEQ; + req->cancel_seq_set = true; req->work.cancel_seq = sequence; return false; } --- a/io_uring/io_uring.c +++ b/io_uring/io_uring.c @@ -2211,6 +2211,7 @@ static int io_init_req(struct io_ring_ct req->file = NULL; req->rsrc_node = NULL; req->task = current; + req->cancel_seq_set = false;
if (unlikely(opcode >= IORING_OP_LAST)) { req->opcode = 0;