The patch below does not apply to the 4.9-stable tree. If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to stable@vger.kernel.org.
thanks,
greg k-h
------------------ original commit in Linus's tree ------------------
From 5369a762c882c0b6e9599e4ebbb3a9ba9eee7e2d Mon Sep 17 00:00:00 2001
From: Theodore Ts'o tytso@mit.edu Date: Wed, 13 Jun 2018 00:23:11 -0400 Subject: [PATCH] ext4: add corruption check in ext4_xattr_set_entry()
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 Cc: stable@kernel.org
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)