[PATCH 1/3] ext4: forbid i_extra_isize not divisible by 4
flat view
STALE3597d
From: Eric Biggers <hidden>
Date: 2016-11-27 06:41:00
Subsystem:
ext4 file system, filesystems (vfs and infrastructure), the rest · Maintainers:
"Theodore Ts'o", Alexander Viro, Christian Brauner, Linus Torvalds
i_extra_isize not divisible by 4 is problematic for several reasons: - It causes the in-inode xattr space to be misaligned, but the xattr header and entries are not declared __packed to express this possibility. This may cause poor performance or incorrect code generation on some platforms. - When validating the xattr entries we can read past the end of the inode if the size available for xattrs is not a multiple of 4. - It allows the nonsensical i_extra_isize=1, which doesn't even leave enough room for i_extra_isize itself. Therefore, update ext4_iget() to consider i_extra_isize not divisible by 4 to be an error, like the case where i_extra_isize is too large. This also matches the rule recently added to e2fsck for determining whether an inode has valid i_extra_isize. This patch shouldn't have any noticeable effect on non-corrupted/non-malicious filesystems, since the size of ext4_inode has always been a multiple of 4. Signed-off-by: Eric Biggers <redacted> --- fs/ext4/inode.c | 11 +++++++---- 1 file changed, 7 insertions(+), 4 deletions(-)
diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c
index 861f848..bc99ebe 100644
--- a/fs/ext4/inode.c
+++ b/fs/ext4/inode.c@@ -4564,10 +4564,12 @@ struct inode *ext4_iget(struct super_block *sb, unsigned long ino) if (EXT4_INODE_SIZE(inode->i_sb) > EXT4_GOOD_OLD_INODE_SIZE) { ei->i_extra_isize = le16_to_cpu(raw_inode->i_extra_isize); if (EXT4_GOOD_OLD_INODE_SIZE + ei->i_extra_isize > - EXT4_INODE_SIZE(inode->i_sb)) { - EXT4_ERROR_INODE(inode, "bad extra_isize (%u != %u)", - EXT4_GOOD_OLD_INODE_SIZE + ei->i_extra_isize, - EXT4_INODE_SIZE(inode->i_sb)); + EXT4_INODE_SIZE(inode->i_sb) || + (ei->i_extra_isize & 3)) { + EXT4_ERROR_INODE(inode, + "bad extra_isize %u (inode size %u)", + ei->i_extra_isize, + EXT4_INODE_SIZE(inode->i_sb)); ret = -EFSCORRUPTED; goto bad_inode; }
@@ -4685,6 +4687,7 @@ struct inode *ext4_iget(struct super_block *sb, unsigned long ino) if (EXT4_INODE_SIZE(inode->i_sb) > EXT4_GOOD_OLD_INODE_SIZE) { if (ei->i_extra_isize == 0) { /* The extra space is currently unused. Use it. */ + BUILD_BUG_ON(sizeof(struct ext4_inode) & 3); ei->i_extra_isize = sizeof(struct ext4_inode) - EXT4_GOOD_OLD_INODE_SIZE; } else {
--
2.8.0.rc3.226.g39d4020