ext4: CVE-2018-10877

ext4: verify the depth of extent tree in ext4_find_extent()

Reference:
https://nvd.nist.gov/vuln/detail/CVE-2018-10877
https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?h=linux-4.14.y&id=d69a9df614fc68741efcb0fcc020f05caa99d668

Change-Id: Ib5d6b1a6167e46d985e01733eae2699696703b67
Signed-off-by: Andreas Wellving <andreas.wellving@enea.com>

1 files changed, 59 insertions, 0 deletions

diff --git a/patches/cve/CVE-2018-10877-ext4-verify-the-depth-of-extent-tree-in-ext4_find_ex.patch b/patches/cve/CVE-2018-10877-ext4-verify-the-depth-of-extent-tree-in-ext4_find_ex.patch
new file mode 100644
index 0000000..d0ce723
--- /dev/null
+++ b/patches/cve/CVE-2018-10877-ext4-verify-the-depth-of-extent-tree-in-ext4_find_ex.patch
@@ -0,0 +1,59 @@
+From d69a9df614fc68741efcb0fcc020f05caa99d668 Mon Sep 17 00:00:00 2001
+From: Theodore Ts'o <tytso@mit.edu>
+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
+
+CVE: CVE-2018-10877
+Upstream-Status: Backport [https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?h=linux-4.14.y&id=d69a9df614fc68741efcb0fcc020f05caa99d668]
+
+Signed-off-by: Theodore Ts'o <tytso@mit.edu>
+Cc: stable@kernel.org
+Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
+Signed-off-by: Andreas Wellving <andreas.wellving@enea.com>
+---
+ 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 8ecf84b8f5a1..a284fb28944b 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 883e89a903d1..5592b7726241 100644
+--- a/fs/ext4/extents.c
++++ b/fs/ext4/extents.c
+@@ -881,6 +881,12 @@ ext4_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 = -EFSCORRUPTED;
++               goto err;
++       }
+ 
+        if (path) {
+                ext4_ext_drop_refs(path);
+-- 
+2.20.1
+