Subject: CVE-2021-47077: scsi: qedf: Add pointer checks in qedf_update_link_speed()

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

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

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

scsi: qedf: Add pointer checks in qedf_update_link_speed()

The following trace was observed:

 [   14.042059] Call Trace:
 [   14.042061]  <IRQ>
 [   14.042068]  qedf_link_update+0x144/0x1f0 [qedf]
 [   14.042117]  qed_link_update+0x5c/0x80 [qed]
 [   14.042135]  qed_mcp_handle_link_change+0x2d2/0x410 [qed]
 [   14.042155]  ? qed_set_ptt+0x70/0x80 [qed]
 [   14.042170]  ? qed_set_ptt+0x70/0x80 [qed]
 [   14.042186]  ? qed_rd+0x13/0x40 [qed]
 [   14.042205]  qed_mcp_handle_events+0x437/0x690 [qed]
 [   14.042221]  ? qed_set_ptt+0x70/0x80 [qed]
 [   14.042239]  qed_int_sp_dpc+0x3a6/0x3e0 [qed]
 [   14.042245]  tasklet_action_common.isra.14+0x5a/0x100
 [   14.042250]  __do_softirq+0xe4/0x2f8
 [   14.042253]  irq_exit+0xf7/0x100
 [   14.042255]  do_IRQ+0x7f/0xd0
 [   14.042257]  common_interrupt+0xf/0xf
 [   14.042259]  </IRQ>

API qedf_link_update() is getting called from QED but by that time
shost_data is not initialised. This results in a NULL pointer dereference
when we try to dereference shost_data while updating supported_speeds.

Add a NULL pointer check before dereferencing shost_data.

The Linux kernel CVE team has assigned CVE-2021-47077 to this issue.

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

	Issue introduced in 4.11 with commit 61d8658b4a43 and fixed in 5.10.40 with commit a6362a737572
	Issue introduced in 4.11 with commit 61d8658b4a43 and fixed in 5.12.7 with commit 11014efcec37
	Issue introduced in 4.11 with commit 61d8658b4a43 and fixed in 5.13 with commit 73578af92a0f

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-2021-47077
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/scsi/qedf/qedf_main.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/a6362a737572f66051deb7637f3f77ddf7a4402f
	https://git.kernel.org/stable/c/11014efcec378bb0050a6cf08eaf375e3693400a
	https://git.kernel.org/stable/c/73578af92a0fae6609b955fcc9113e50e413c80f