linux-kernel - [PATCH 6.8 606/715] ovl: relax WARN_ON in ovl_verify

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Date: Sun, 24 Mar 2024 18:33:05 -0400
From: Sasha Levin <sashal@...nel.org>
To: linux-kernel@...r.kernel.org,
	stable@...r.kernel.org
Cc: Amir Goldstein <amir73il@...il.com>,
	syzbot+3abd99031b42acf367ef@...kaller.appspotmail.com,
	Sasha Levin <sashal@...nel.org>
Subject: [PATCH 6.8 606/715] ovl: relax WARN_ON in ovl_verify_area()

From: Amir Goldstein <amir73il@...il.com>

[ Upstream commit 77a28aa476873048024ad56daf8f4f17d58ee48e ]

syzbot hit an assertion in copy up data loop which looks like it is
the result of a lower file whose size is being changed underneath
overlayfs.

This type of use case is documented to cause undefined behavior, so
returning EIO error for the copy up makes sense, but it should not be
causing a WARN_ON assertion.

Reported-and-tested-by: syzbot+3abd99031b42acf367ef@...kaller.appspotmail.com
Fixes: ca7ab482401c ("ovl: add permission hooks outside of do_splice_direct()")
Signed-off-by: Amir Goldstein <amir73il@...il.com>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 fs/overlayfs/copy_up.c | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/fs/overlayfs/copy_up.c b/fs/overlayfs/copy_up.c
index 8586e2f5d2439..0762575a1e708 100644
--- a/fs/overlayfs/copy_up.c
+++ b/fs/overlayfs/copy_up.c
@@ -234,11 +234,11 @@ static int ovl_verify_area(loff_t pos, loff_t pos2, loff_t len, loff_t totlen)
 {
 	loff_t tmp;
 
-	if (WARN_ON_ONCE(pos != pos2))
+	if (pos != pos2)
 		return -EIO;
-	if (WARN_ON_ONCE(pos < 0 || len < 0 || totlen < 0))
+	if (pos < 0 || len < 0 || totlen < 0)
 		return -EIO;
-	if (WARN_ON_ONCE(check_add_overflow(pos, len, &tmp)))
+	if (check_add_overflow(pos, len, &tmp))
 		return -EIO;
 	return 0;
 }
-- 
2.43.0