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authorTheodore Ts'o <tytso@mit.edu>2018-06-13 00:51:28 -0400
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>2018-07-11 16:31:29 +0200
commit11f6b0e426aa5d85df5e9cad74a55b407b5be007 (patch)
tree0e4d990539bbbe14bec0af5529e33553e703b574
parente4130b9612095a6db9bafb90634fbd579b77d893 (diff)
ext4: always verify the magic number in xattr blocks
commit 513f86d73855ce556ea9522b6bfd79f87356dc3a upstream. If there an inode points to a block which is also some other type of metadata block (such as a block allocation bitmap), the buffer_verified flag can be set when it was validated as that other metadata block type; however, it would make a really terrible external attribute block. The reason why we use the verified flag is to avoid constantly reverifying the block. However, it doesn't take much overhead to make sure the magic number of the xattr block is correct, and this will avoid potential crashes. This addresses CVE-2018-10879. https://bugzilla.kernel.org/show_bug.cgi?id=200001 Signed-off-by: Theodore Ts'o <tytso@mit.edu> Reviewed-by: Andreas Dilger <adilger@dilger.ca> Cc: stable@kernel.org Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
-rw-r--r--fs/ext4/xattr.c6
1 files changed, 3 insertions, 3 deletions
diff --git a/fs/ext4/xattr.c b/fs/ext4/xattr.c
index 230ba79715f6..0263692979ec 100644
--- a/fs/ext4/xattr.c
+++ b/fs/ext4/xattr.c
@@ -230,12 +230,12 @@ __ext4_xattr_check_block(struct inode *inode, struct buffer_head *bh,
{
int error = -EFSCORRUPTED;
- if (buffer_verified(bh))
- return 0;
-
if (BHDR(bh)->h_magic != cpu_to_le32(EXT4_XATTR_MAGIC) ||
BHDR(bh)->h_blocks != cpu_to_le32(1))
goto errout;
+ if (buffer_verified(bh))
+ return 0;
+
error = -EFSBADCRC;
if (!ext4_xattr_block_csum_verify(inode, bh))
goto errout;