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From: Theodore Ts'o <tytso@mit.edu>
Date: Wed, 13 Jun 2018 00:23:11 -0400
Subject: ext4: add corruption check in ext4_xattr_set_entry()
Origin: https://git.kernel.org/pub/scm/linux/kernel/git/tytso/ext4.git/commit?id=4fda60bbdbb61de76e3d3c48ed77c9e9b96b00d1
Bug-Debian-Security: https://security-tracker.debian.org/tracker/CVE-2018-10879
In theory this should have been caught earlier when the xattr list was
verified, but in case it got missed, it's simple enough to add check
to make sure we don't overrun the xattr buffer.
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>
---
fs/ext4/xattr.c | 10 ++++++++--
1 file changed, 8 insertions(+), 2 deletions(-)
diff --git a/fs/ext4/xattr.c b/fs/ext4/xattr.c
index fc4ced59c565..230ba79715f6 100644
--- a/fs/ext4/xattr.c
+++ b/fs/ext4/xattr.c
@@ -1560,7 +1560,7 @@ static int ext4_xattr_set_entry(struct ext4_xattr_info *i,
handle_t *handle, struct inode *inode,
bool is_block)
{
- struct ext4_xattr_entry *last;
+ struct ext4_xattr_entry *last, *next;
struct ext4_xattr_entry *here = s->here;
size_t min_offs = s->end - s->base, name_len = strlen(i->name);
int in_inode = i->in_inode;
@@ -1595,7 +1595,13 @@ static int ext4_xattr_set_entry(struct ext4_xattr_info *i,
/* Compute min_offs and last. */
last = s->first;
- for (; !IS_LAST_ENTRY(last); last = EXT4_XATTR_NEXT(last)) {
+ for (; !IS_LAST_ENTRY(last); last = next) {
+ next = EXT4_XATTR_NEXT(last);
+ if ((void *)next >= s->end) {
+ EXT4_ERROR_INODE(inode, "corrupted xattr entries");
+ ret = -EFSCORRUPTED;
+ goto out;
+ }
if (!last->e_value_inum && last->e_value_size) {
size_t offs = le16_to_cpu(last->e_value_offs);
if (offs < min_offs)
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