The sequence for timeout req may overflow, and it will lead to wrong
order of timeout req list. And we should consider two situation:
1. ctx->cached_sq_head + count - 1 may overflow;
2. cached_sq_head of now may overflow compare with before
cached_sq_head.
Fix the wrong logic by add record of count and use type long long to
record the overflow.
Signed-off-by: yangerkun <yangerkun@xxxxxxxxxx>
---
fs/io_uring.c | 31 +++++++++++++++++++++++++------
1 file changed, 25 insertions(+), 6 deletions(-)
diff --git a/fs/io_uring.c b/fs/io_uring.c
index 76fdbe84aff5..9cc96f68b370 100644
--- a/fs/io_uring.c
+++ b/fs/io_uring.c
@@ -288,6 +288,7 @@ struct io_poll_iocb {
struct io_timeout {
struct file *file;
struct hrtimer timer;
+ unsigned count;
};
/*
@@ -1884,7 +1885,7 @@ static enum hrtimer_restart io_timeout_fn(struct hrtimer *timer)
static int io_timeout(struct io_kiocb *req, const struct io_uring_sqe *sqe)
{
- unsigned count, req_dist, tail_index;
+ unsigned count;
struct io_ring_ctx *ctx = req->ctx;
struct list_head *entry;
struct timespec64 ts;
@@ -1907,21 +1908,39 @@ static int io_timeout(struct io_kiocb *req, const struct io_uring_sqe *sqe)
count = 1;
req->sequence = ctx->cached_sq_head + count - 1;
+ req->timeout.count = count;
req->flags |= REQ_F_TIMEOUT;
/*
* Insertion sort, ensuring the first entry in the list is always
* the one we need first.
*/
- tail_index = ctx->cached_cq_tail - ctx->rings->sq_dropped;
- req_dist = req->sequence - tail_index;
spin_lock_irq(&ctx->completion_lock);
list_for_each_prev(entry, &ctx->timeout_list) {
struct io_kiocb *nxt = list_entry(entry, struct io_kiocb, list);
- unsigned dist;
+ unsigned nxt_sq_head;
+ long long tmp, tmp_nxt;
- dist = nxt->sequence - tail_index;
- if (req_dist >= dist)
+ /* count bigger than before should break directly. */
+ if (count >= nxt->timeout.count)
+ break;
+
+ /*
+ * Since cached_sq_head + count - 1 can overflow, use type long
+ * long to store it.
+ */
+ tmp = (long long)ctx->cached_sq_head + count - 1;
+ nxt_sq_head = nxt->sequence - nxt->timeout.count + 1;
+ tmp_nxt = (long long)nxt_sq_head + nxt->timeout.count - 1;
+
+ /*
+ * cached_sq_head may overflow, and it will never overflow twice
+ * once there is some timeout req still be valid.
+ */
+ if (ctx->cached_sq_head < nxt_sq_head)
+ tmp_nxt += UINT_MAX;
+
+ if (tmp >= tmp_nxt)
break;
}
list_add(&req->list, entry);
--
2.17.2
