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io_uring: fix cancellation overwriting req->flags

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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: 521223d7c2 ("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.1718323430.git.asml.silence@gmail.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>
This commit is contained in:
Pavel Begunkov 2024-06-14 01:04:29 +01:00 committed by Jens Axboe
parent 54559642b9
commit f4a1254f2a
3 changed files with 5 additions and 3 deletions
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3
include/linux/io_uring_types.h
View File

@ -648,7 +648,7 @@ 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;
@ -657,6 +657,7 @@ 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;

4
io_uring/cancel.h
View File

@ -27,10 +27,10 @@ bool io_cancel_req_match(struct io_kiocb *req, struct io_cancel_data *cd);
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;
}

1
io_uring/io_uring.c
View File

@ -2058,6 +2058,7 @@ static int io_init_req(struct io_ring_ctx *ctx, struct io_kiocb *req,
req->file = NULL;
req->rsrc_node = NULL;
req->task = current;
req->cancel_seq_set = false;
if (unlikely(opcode >= IORING_OP_LAST)) {
req->opcode = 0;