From 722d94847de29310e8aa03fcbdb41fc92c521756 Mon Sep 17 00:00:00 2001

From: Jamie Hill-Daniel <jamie@hill-daniel.co.uk>

Date: Tue, 18 Jan 2022 08:06:04 +0100

Subject: [PATCH] vfs: fs_context: fix up param length parsing in

 legacy_parse_param

References: CVE-2022-0185 bsc#1194517

Patch-mainline: v5.17-rc1

Git-commit: 722d94847de29310e8aa03fcbdb41fc92c521756

The "PAGE_SIZE - 2 - size" calculation in legacy_parse_param() is an

unsigned type so a large value of "size" results in a high positive

value instead of a negative value as expected.  Fix this by getting rid

of the subtraction.

Signed-off-by: Jamie Hill-Daniel <jamie@hill-daniel.co.uk>

Signed-off-by: William Liu <willsroot@protonmail.com>

Tested-by: Salvatore Bonaccorso <carnil@debian.org>

Tested-by: Thadeu Lima de Souza Cascardo <cascardo@canonical.com>

Acked-by: Dan Carpenter <dan.carpenter@oracle.com>

Acked-by: Al Viro <viro@zeniv.linux.org.uk>

Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

Acked-by: David Disseldorp <ddiss@suse.de>

---

 fs/fs_context.c | 2 +-

 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/fs/fs_context.c b/fs/fs_context.c

index b7e43a780a62..24ce12f0db32 100644

--- a/fs/fs_context.c

+++ b/fs/fs_context.c

@@ -548,7 +548,7 @@ static int legacy_parse_param(struct fs_context *fc, struct fs_parameter *param)

 			      param->key);

 	}

-	if (len > PAGE_SIZE - 2 - size)

+	if (size + len + 2 > PAGE_SIZE)

 		return invalf(fc, "VFS: Legacy: Cumulative options too large");

 	if (strchr(param->key, ',') ||

 	    (param->type == fs_value_is_string &&

-- 

2.31.1