linux-kernel - [PATCH] block: Fix WARNING in _copy_from

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [thread-next>] [day] [month] [year] [list]

Message-Id: <20240121202634.275068-1-lk@c--e.de>
Date: Sun, 21 Jan 2024 21:26:34 +0100
From: "Christian A. Ehrhardt" <lk@...e.de>
To: linux-block@...r.kernel.org,
	linux-kernel@...r.kernel.org
Cc: "Christian A. Ehrhardt" <lk@...e.de>,
	syzbot+a532b03fdfee2c137666@...kaller.appspotmail.com,
	syzbot+63dec323ac56c28e644f@...kaller.appspotmail.com,
	Jens Axboe <axboe@...nel.dk>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Alexander Viro <viro@...iv.linux.org.uk>
Subject: [PATCH] block: Fix WARNING in _copy_from_iter

Syzkaller reports a warning in _copy_from_iter because an
iov_iter is supposedly used in the wrong direction. The reason
is that syzcaller managed to generate a request with
a transfer direction of SG_DXFER_TO_FROM_DEV. This instructs
the kernel to copy user buffers into the kernel, read into
the copied buffers and then copy the data back to user space.

Thus the iovec is used in both directions.

Detect this situation in the block layer and construct a new
iterator with the correct direction for the copy-in.

Reported-by: syzbot+a532b03fdfee2c137666@...kaller.appspotmail.com
Closes: https://lore.kernel.org/lkml/0000000000009b92c10604d7a5e9@google.com/t/
Reported-by: syzbot+63dec323ac56c28e644f@...kaller.appspotmail.com
Closes: https://lore.kernel.org/lkml/0000000000003faaa105f6e7c658@google.com/T/
Signed-off-by: Christian A. Ehrhardt <lk@...e.de>
---
 block/blk-map.c | 13 ++++++++++---
 1 file changed, 10 insertions(+), 3 deletions(-)

diff --git a/block/blk-map.c b/block/blk-map.c
index 8584babf3ea0..71210cdb3442 100644
--- a/block/blk-map.c
+++ b/block/blk-map.c
@@ -205,12 +205,19 @@ static int bio_copy_user_iov(struct request *rq, struct rq_map_data *map_data,
 	/*
 	 * success
 	 */
-	if ((iov_iter_rw(iter) == WRITE &&
-	     (!map_data || !map_data->null_mapped)) ||
-	    (map_data && map_data->from_user)) {
+	if (iov_iter_rw(iter) == WRITE &&
+	     (!map_data || !map_data->null_mapped)) {
 		ret = bio_copy_from_iter(bio, iter);
 		if (ret)
 			goto cleanup;
+	} else if (map_data && map_data->from_user) {
+		struct iov_iter iter2 = *iter;
+
+		/* This is the copy-in part of SG_DXFER_TO_FROM_DEV. */
+		iter2.data_source = ITER_SOURCE;
+		ret = bio_copy_from_iter(bio, &iter2);
+		if (ret)
+			goto cleanup;
 	} else {
 		if (bmd->is_our_pages)
 			zero_fill_bio(bio);
-- 
2.40.1