Subject: CVE-2021-47585: btrfs: fix memory leak in __add_inode_ref()

From: Greg Kroah-Hartman <[email-masked]>

Description
===========

In the Linux kernel, the following vulnerability has been resolved:

btrfs: fix memory leak in __add_inode_ref()

Line 1169 (#3) allocates a memory chunk for victim_name by kmalloc(),
but  when the function returns in line 1184 (#4) victim_name allocated
by line 1169 (#3) is not freed, which will lead to a memory leak.
There is a similar snippet of code in this function as allocating a memory
chunk for victim_name in line 1104 (#1) as well as releasing the memory
in line 1116 (#2).

We should kfree() victim_name when the return value of backref_in_log()
is less than zero and before the function returns in line 1184 (#4).

1057 static inline int __add_inode_ref(struct btrfs_trans_handle *trans,
1058 				  struct btrfs_root *root,
1059 				  struct btrfs_path *path,
1060 				  struct btrfs_root *log_root,
1061 				  struct btrfs_inode *dir,
1062 				  struct btrfs_inode *inode,
1063 				  u64 inode_objectid, u64 parent_objectid,
1064 				  u64 ref_index, char *name, int namelen,
1065 				  int *search_done)
1066 {

1104 	victim_name = kmalloc(victim_name_len, GFP_NOFS);
	// #1: kmalloc (victim_name-1)
1105 	if (!victim_name)
1106 		return -ENOMEM;

1112	ret = backref_in_log(log_root, &search_key,
1113			parent_objectid, victim_name,
1114			victim_name_len);
1115	if (ret < 0) {
1116		kfree(victim_name); // #2: kfree (victim_name-1)
1117		return ret;
1118	} else if (!ret) {

1169 	victim_name = kmalloc(victim_name_len, GFP_NOFS);
	// #3: kmalloc (victim_name-2)
1170 	if (!victim_name)
1171 		return -ENOMEM;

1180 	ret = backref_in_log(log_root, &search_key,
1181 			parent_objectid, victim_name,
1182 			victim_name_len);
1183 	if (ret < 0) {
1184 		return ret; // #4: missing kfree (victim_name-2)
1185 	} else if (!ret) {

1241 	return 0;
1242 }

The Linux kernel CVE team has assigned CVE-2021-47585 to this issue.

Affected and fixed versions
===========================

	Issue introduced in 5.5 with commit d3316c8233bb and fixed in 5.10.88 with commit 005d9292b5b2
	Issue introduced in 5.5 with commit d3316c8233bb and fixed in 5.15.11 with commit 493ff661d434
	Issue introduced in 5.5 with commit d3316c8233bb and fixed in 5.16 with commit f35838a69302

Please see https://www.kernel.org for a full list of currently supported
kernel versions by the kernel community.

Unaffected versions might change over time as fixes are backported to
older supported kernel versions.  The official CVE entry at
	https://cve.org/CVERecord/?id=CVE-2021-47585
will be updated if fixes are backported, please check that for the most
up to date information about this issue.

Affected files
==============

The file(s) affected by this issue are:
	fs/btrfs/tree-log.c

Mitigation
==========

The Linux kernel CVE team recommends that you update to the latest
stable kernel version for this, and many other bugfixes.  Individual
changes are never tested alone, but rather are part of a larger kernel
release.  Cherry-picking individual commits is not recommended or
supported by the Linux kernel community at all.  If however, updating to
the latest release is impossible, the individual changes to resolve this
issue can be found at these commits:
	https://git.kernel.org/stable/c/005d9292b5b2e71a009f911bd85d755009b37242
	https://git.kernel.org/stable/c/493ff661d434d6bdf02e3a21adae04d7a0b4265d
	https://git.kernel.org/stable/c/f35838a6930296fc1988764cfa54cb3f705c0665