ext4: check for NUL characters in extended attribute's name

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 <[email protected]> Signed-off-by: Theodore Ts'o <[email protected]> Cc: [email protected] Signed-off-by: Greg Kroah-Hartman <[email protected]>
klaby · Sep 5, 2018 · 9c2860f · 9c2860f
1 parent 1ad4098
commit 9c2860f
Showing 1 changed file with 2 additions and 0 deletions.
diff --git a/fs/ext4/xattr.c b/fs/ext4/xattr.c
@@ -184,6 +184,8 @@ ext4_xattr_check_names(struct ext4_xattr_entry *entry, void *end,
 		struct ext4_xattr_entry *next = EXT4_XATTR_NEXT(e);
 		if ((void *)next >= end)
 			return -EFSCORRUPTED;
+		if (strnlen(e->e_name, e->e_name_len) != e->e_name_len)
+			return -EFSCORRUPTED;
 		e = next;
 	}