Subject: CVE-2021-46956: virtiofs: fix memory leak in virtio_fs_probe()

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

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

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

virtiofs: fix memory leak in virtio_fs_probe()

When accidentally passing twice the same tag to qemu, kmemleak ended up
reporting a memory leak in virtiofs.  Also, looking at the log I saw the
following error (that's when I realised the duplicated tag):

  virtiofs: probe of virtio5 failed with error -17

Here's the kmemleak log for reference:

unreferenced object 0xffff888103d47800 (size 1024):
  comm "systemd-udevd", pid 118, jiffies 4294893780 (age 18.340s)
  hex dump (first 32 bytes):
    00 00 00 00 ad 4e ad de ff ff ff ff 00 00 00 00  .....N..........
    ff ff ff ff ff ff ff ff 80 90 02 a0 ff ff ff ff  ................
  backtrace:
    [<000000000ebb87c1>] virtio_fs_probe+0x171/0x7ae [virtiofs]
    [<00000000f8aca419>] virtio_dev_probe+0x15f/0x210
    [<000000004d6baf3c>] really_probe+0xea/0x430
    [<00000000a6ceeac8>] device_driver_attach+0xa8/0xb0
    [<00000000196f47a7>] __driver_attach+0x98/0x140
    [<000000000b20601d>] bus_for_each_dev+0x7b/0xc0
    [<00000000399c7b7f>] bus_add_driver+0x11b/0x1f0
    [<0000000032b09ba7>] driver_register+0x8f/0xe0
    [<00000000cdd55998>] 0xffffffffa002c013
    [<000000000ea196a2>] do_one_initcall+0x64/0x2e0
    [<0000000008f727ce>] do_init_module+0x5c/0x260
    [<000000003cdedab6>] __do_sys_finit_module+0xb5/0x120
    [<00000000ad2f48c6>] do_syscall_64+0x33/0x40
    [<00000000809526b5>] entry_SYSCALL_64_after_hwframe+0x44/0xae

The Linux kernel CVE team has assigned CVE-2021-46956 to this issue.

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

	Issue introduced in 5.4 with commit a62a8ef9d97d and fixed in 5.4.118 with commit 310efc95c72c
	Issue introduced in 5.4 with commit a62a8ef9d97d and fixed in 5.10.36 with commit d19555ff225d
	Issue introduced in 5.4 with commit a62a8ef9d97d and fixed in 5.11.20 with commit 9b9d60c0eb8a
	Issue introduced in 5.4 with commit a62a8ef9d97d and fixed in 5.12.3 with commit 5116e79fc6e6
	Issue introduced in 5.4 with commit a62a8ef9d97d and fixed in 5.13 with commit c79c5e017892

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-2021-46956
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/fuse/virtio_fs.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/310efc95c72c13faf855c692d19cd4d054d827c8
	https://git.kernel.org/stable/c/d19555ff225d0896a33246a49279e6d578095f15
	https://git.kernel.org/stable/c/9b9d60c0eb8ada99cce2a9ab5c15dffc523b01ae
	https://git.kernel.org/stable/c/5116e79fc6e6725b8acdad8b7e928a83ab7b47e6
	https://git.kernel.org/stable/c/c79c5e0178922a9e092ec8fed026750f39dcaef4