Subject: CVE-2021-4441: spi: spi-zynq-qspi: Fix a NULL pointer dereference in zynq_qspi_exec_mem_op()

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

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

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

spi: spi-zynq-qspi: Fix a NULL pointer dereference in zynq_qspi_exec_mem_op()

In zynq_qspi_exec_mem_op(), kzalloc() is directly used in memset(),
which could lead to a NULL pointer dereference on failure of
kzalloc().

Fix this bug by adding a check of tmpbuf.

This bug was found by a static analyzer. The analysis employs
differential checking to identify inconsistent security operations
(e.g., checks or kfrees) between two code paths and confirms that the
inconsistent operations are not recovered in the current function or
the callers, so they constitute bugs.

Note that, as a bug found by static analysis, it can be a false
positive or hard to trigger. Multiple researchers have cross-reviewed
the bug.

Builds with CONFIG_SPI_ZYNQ_QSPI=m show no new warnings,
and our static analyzer no longer warns about this code.

The Linux kernel CVE team has assigned CVE-2021-4441 to this issue.

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

	Issue introduced in 5.2 with commit 67dca5e580f1 and fixed in 5.4.182 with commit df14d2bed8e2
	Issue introduced in 5.2 with commit 67dca5e580f1 and fixed in 5.10.103 with commit 2efece1368ae
	Issue introduced in 5.2 with commit 67dca5e580f1 and fixed in 5.15.26 with commit 3c32405d6474
	Issue introduced in 5.2 with commit 67dca5e580f1 and fixed in 5.16.12 with commit b9dd08cbebe0
	Issue introduced in 5.2 with commit 67dca5e580f1 and fixed in 5.17 with commit ab3824427b84

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-2021-4441
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/spi/spi-zynq-qspi.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/df14d2bed8e2455878e046e67123d9ecb2e79056
	https://git.kernel.org/stable/c/2efece1368aeee2d2552c7ec36aeb676c4d4c95f
	https://git.kernel.org/stable/c/3c32405d6474a21f7d742828e73c13e326dcae82
	https://git.kernel.org/stable/c/b9dd08cbebe0c593c49bf86d2012a431494e54cb
	https://git.kernel.org/stable/c/ab3824427b848da10e9fe2727f035bbeecae6ff4