From: Jens Axboe <axboe@kernel.dk>
Date: Sat, 26 Oct 2019 13:22:55 +0000 (-0600)
Subject: io_uring: protect fixed file indexing with array_index_nospec()
X-Git-Url: http://git.maquefel.me/?a=commitdiff_plain;h=b7620121dc04e44ce654297050f9eaf39d414a34;p=linux.git

io_uring: protect fixed file indexing with array_index_nospec()

We index the file tables with a user given value. After we check
it's within our limits, use array_index_nospec() to prevent any
spectre attacks here.

Suggested-by: Jann Horn <jannh@google.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
---

diff --git a/fs/io_uring.c b/fs/io_uring.c
index b668149c20b9a..7743b180a3e0a 100644
--- a/fs/io_uring.c
+++ b/fs/io_uring.c
@@ -2321,6 +2321,7 @@ static int io_req_set_file(struct io_ring_ctx *ctx, const struct sqe_submit *s,
 		if (unlikely(!ctx->user_files ||
 		    (unsigned) fd >= ctx->nr_user_files))
 			return -EBADF;
+		fd = array_index_nospec(fd, ctx->nr_user_files);
 		if (!ctx->user_files[fd])
 			return -EBADF;
 		req->file = ctx->user_files[fd];