From: Jens Axboe <axboe@kernel.dk>
Date: Tue, 23 Aug 2022 13:26:08 +0000 (-0600)
Subject: io_uring: fix off-by-one in sync cancelation file check
X-Git-Url: http://git.maquefel.me/?a=commitdiff_plain;h=47abea041f897d64dbd5777f0cf7745148f85d75;p=linux.git

io_uring: fix off-by-one in sync cancelation file check

The passed in index should be validated against the number of registered
files we have, it needs to be smaller than the index value to avoid going
one beyond the end.

Fixes: 78a861b94959 ("io_uring: add sync cancelation API through io_uring_register()")
Reported-by: Luo Likang <luolikang@nsfocus.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
---

diff --git a/io_uring/cancel.c b/io_uring/cancel.c
index e4e1dc0325f0c..5fc5d3e80fcb3 100644
--- a/io_uring/cancel.c
+++ b/io_uring/cancel.c
@@ -218,7 +218,7 @@ static int __io_sync_cancel(struct io_uring_task *tctx,
 	    (cd->flags & IORING_ASYNC_CANCEL_FD_FIXED)) {
 		unsigned long file_ptr;
 
-		if (unlikely(fd > ctx->nr_user_files))
+		if (unlikely(fd >= ctx->nr_user_files))
 			return -EBADF;
 		fd = array_index_nospec(fd, ctx->nr_user_files);
 		file_ptr = io_fixed_file_slot(&ctx->file_table, fd)->file_ptr;