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FAILED: patch "[PATCH] ext4: add corruption check in ext4_xattr_set_entry()" failed to apply to 4.9-stable tree

PATCH [email protected] 1 participant 1 message Jul 10, 2018

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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 <[email protected]>.

thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

Quoted 1 line

From 5369a762c882c0b6e9599e4ebbb3a9ba9eee7e2d Mon Sep 17 00:00:00 2001

From: Theodore Ts'o <[email protected]>
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 <[email protected]>
Reviewed-by Andreas Dilger <[email protected]>
Cc [email protected]
fs/ext4/xattr.c +8 -2
index fc4ced59c565..230ba79715f6 100644
@@ -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)