Commit 3851d25c75ed0 ("io_uring: check for rollover of buffer ID when
providing buffers") introduced a check to prevent wrapping the BID
counter when sqe->off is provided, but it's off-by-one too
restrictive, rejecting the last possible BID (65534).
i.e., the following fails with -EINVAL.
io_uring_prep_provide_buffers(sqe, addr, size, 0xFFFF, 0, 0);
Fixes: 3851d25c75ed ("io_uring: check for rollover of buffer ID when providing buffers")
Signed-off-by: Gabriel Krisman Bertazi <krisman@xxxxxxx>
---
io_uring/kbuf.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/io_uring/kbuf.c b/io_uring/kbuf.c
index 556f4df25b0f..52dba81c3f50 100644
--- a/io_uring/kbuf.c
+++ b/io_uring/kbuf.c
@@ -352,7 +352,7 @@ int io_provide_buffers_prep(struct io_kiocb *req, const struct io_uring_sqe *sqe
tmp = READ_ONCE(sqe->off);
if (tmp > USHRT_MAX)
return -E2BIG;
- if (tmp + p->nbufs >= USHRT_MAX)
+ if (tmp + p->nbufs > USHRT_MAX)
return -EINVAL;
p->bid = tmp;
return 0;
--
2.42.0
