From c3cccec63f1ab88843ceaee5d54e74cbf858f77c Mon Sep 17 00:00:00 2001 From: Theodore Ts'o Date: Thu, 14 Jun 2018 12:55:10 -0400 Subject: [PATCH] ext4: verify the depth of extent tree in ext4_find_extent() 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 [bwh: Backported to 3.16: return -EIO instead of -EFSCORRUPTED] Signed-off-by: Ben Hutchings --- fs/ext4/ext4_extents.h | 1 + fs/ext4/extents.c | 6 ++++++ 2 files changed, 7 insertions(+) diff --git a/fs/ext4/ext4_extents.h b/fs/ext4/ext4_extents.h index 51bc821ade90..cda1e2ac94c3 100644 --- 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) + \ diff --git a/fs/ext4/extents.c b/fs/ext4/extents.c index b3dc990e9d18..7f6d65049842 100644 --- a/fs/ext4/extents.c +++ b/fs/ext4/extents.c @@ -795,6 +795,12 @@ ext4_ext_find_extent(struct inode *inode, ext4_lblk_t block, 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; + } /* account possible depth increase */ if (!path) {