linux-kernel - [PATCH 3.16 090/328] ext4: check for NUL characters in extended attribute's name

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Message-ID: <lsq.1544392233.838614446@decadent.org.uk>
Date:   Sun, 09 Dec 2018 21:50:33 +0000
From:   Ben Hutchings <ben@...adent.org.uk>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
CC:     akpm@...ux-foundation.org, "Wen Xu" <wen.xu@...ech.edu>,
        "Theodore Ts'o" <tytso@....edu>
Subject: [PATCH 3.16 090/328] ext4: check for NUL characters in extended
 attribute's name

3.16.62-rc1 review patch.  If anyone has any objections, please let me know.

------------------

From: Theodore Ts'o <tytso@....edu>

commit 7d95178c77014dbd8dce36ee40bbbc5e6c121ff5 upstream.

Extended attribute names are defined to be NUL-terminated, so the name
must not contain a NUL character.  This is important because there are
places when remove extended attribute, the code uses strlen to
determine the length of the entry.  That should probably be fixed at
some point, but code is currently really messy, so the simplest fix
for now is to simply validate that the extended attributes are sane.

https://bugzilla.kernel.org/show_bug.cgi?id=200401

Reported-by: Wen Xu <wen.xu@...ech.edu>
Signed-off-by: Theodore Ts'o <tytso@....edu>
[bwh: Backported to 3.16: return -EIO instead of -EFSCORRUPTED]
Signed-off-by: Ben Hutchings <ben@...adent.org.uk>
---
 fs/ext4/xattr.c | 2 ++
 1 file changed, 2 insertions(+)

--- a/fs/ext4/xattr.c
+++ b/fs/ext4/xattr.c
@@ -193,6 +193,8 @@ ext4_xattr_check_names(struct ext4_xattr
 		struct ext4_xattr_entry *next = EXT4_XATTR_NEXT(e);
 		if ((void *)next >= end)
 			return -EIO;
+		if (strnlen(e->e_name, e->e_name_len) != e->e_name_len)
+			return -EIO;
 		e = next;
 	}