3.18-stable review patch. If anyone has any objections, please let me know. ------------------ From: Theodore Ts'o <tytso@xxxxxxx> commit bc890a60247171294acc0bd67d211fa4b88d40ba upstream. If there is a corupted file system where the claimed depth of the extent tree is -1, this can cause a massive buffer overrun leading to sadness. This addresses CVE-2018-10877. https://bugzilla.kernel.org/show_bug.cgi?id=199417 Signed-off-by: Theodore Ts'o <tytso@xxxxxxx> [bwh: Backported to 3.16: return -EIO instead of -EFSCORRUPTED] Signed-off-by: Ben Hutchings <ben@xxxxxxxxxxxxxxx> Cc: Greg Hackmann <ghackmann@xxxxxxxxxx> Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx> --- fs/ext4/ext4_extents.h | 1 + fs/ext4/extents.c | 6 ++++++ 2 files changed, 7 insertions(+) --- a/fs/ext4/ext4_extents.h +++ b/fs/ext4/ext4_extents.h @@ -103,6 +103,7 @@ struct ext4_extent_header { }; #define EXT4_EXT_MAGIC cpu_to_le16(0xf30a) +#define EXT4_MAX_EXTENT_DEPTH 5 #define EXT4_EXTENT_TAIL_OFFSET(hdr) \ (sizeof(struct ext4_extent_header) + \ --- a/fs/ext4/extents.c +++ b/fs/ext4/extents.c @@ -870,6 +870,12 @@ ext4_find_extent(struct inode *inode, ex eh = ext_inode_hdr(inode); depth = ext_depth(inode); + if (depth < 0 || depth > EXT4_MAX_EXTENT_DEPTH) { + EXT4_ERROR_INODE(inode, "inode has invalid extent depth: %d", + depth); + ret = -EIO; + goto err; + } if (path) { ext4_ext_drop_refs(path);
