From: Jamie Hill-Daniel <jamie@hill-daniel.co.uk>
Date: Tue, 18 Jan 2022 07:06:04 +0000 (+0100)
Subject: vfs: fs_context: fix up param length parsing in legacy_parse_param
X-Git-Tag: archive/raspbian/5.15.15-2+rpi1~1^2~18
X-Git-Url: https://dgit.raspbian.org/?a=commitdiff_plain;h=faf68ffd2f76a3140ce4f1e4cd5a6fe249d41a30;p=linux.git

vfs: fs_context: fix up param length parsing in legacy_parse_param

Origin: https://git.kernel.org/linus/722d94847de29310e8aa03fcbdb41fc92c521756
Bug-Debian-Security: https://security-tracker.debian.org/tracker/CVE-2022-0185

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>

Gbp-Pq: Topic bugfix/all
Gbp-Pq: Name vfs-fs_context-fix-up-param-length-parsing-in-legacy.patch
---

diff --git a/fs/fs_context.c b/fs/fs_context.c
index b7e43a780a6..24ce12f0db3 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 &&