Subject: CVE-2021-47095: ipmi: ssif: initialize ssif_info->client early

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

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

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

ipmi: ssif: initialize ssif_info->client early

During probe ssif_info->client is dereferenced in error path. However,
it is set when some of the error checking has already been done. This
causes following kernel crash if an error path is taken:

[   30.645593][  T674] ipmi_ssif 0-000e: ipmi_ssif: Not probing, Interface already present
[   30.657616][  T674] Unable to handle kernel NULL pointer dereference at virtual address 0000000000000088
...
[   30.657723][  T674] pc : __dev_printk+0x28/0xa0
[   30.657732][  T674] lr : _dev_err+0x7c/0xa0
...
[   30.657772][  T674] Call trace:
[   30.657775][  T674]  __dev_printk+0x28/0xa0
[   30.657778][  T674]  _dev_err+0x7c/0xa0
[   30.657781][  T674]  ssif_probe+0x548/0x900 [ipmi_ssif 62ce4b08badc1458fd896206d9ef69a3c31f3d3e]
[   30.657791][  T674]  i2c_device_probe+0x37c/0x3c0
...

Initialize ssif_info->client before any error path can be taken. Clear
i2c_client data in the error path to prevent the dangling pointer from
leaking.

The Linux kernel CVE team has assigned CVE-2021-47095 to this issue.

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

	Issue introduced in 5.4 with commit c4436c9149c5 and fixed in 5.4.169 with commit 8efd6a3391f7
	Issue introduced in 5.4 with commit c4436c9149c5 and fixed in 5.10.89 with commit 1f6ab847461c
	Issue introduced in 5.4 with commit c4436c9149c5 and fixed in 5.15.12 with commit 77a7311ca167
	Issue introduced in 5.4 with commit c4436c9149c5 and fixed in 5.16 with commit 34f35f8f14bc

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-2021-47095
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:
	drivers/char/ipmi/ipmi_ssif.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/8efd6a3391f7b0b19fb0c38e50add06ca30c94af
	https://git.kernel.org/stable/c/1f6ab847461ce7dd89ae9db2dd4658c993355d7c
	https://git.kernel.org/stable/c/77a7311ca167aa5b7055c549a940a56e73ee5f29
	https://git.kernel.org/stable/c/34f35f8f14bc406efc06ee4ff73202c6fd245d15