Subject: CVE-2021-47081: habanalabs/gaudi: Fix a potential use after free in gaudi_memset_device_memory

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

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

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

habanalabs/gaudi: Fix a potential use after free in gaudi_memset_device_memory

Our code analyzer reported a uaf.

In gaudi_memset_device_memory, cb is get via hl_cb_kernel_create()
with 2 refcount.
If hl_cs_allocate_job() failed, the execution runs into release_cb
branch. One ref of cb is dropped by hl_cb_put(cb) and could be freed
if other thread also drops one ref. Then cb is used by cb->id later,
which is a potential uaf.

My patch add a variable 'id' to accept the value of cb->id before the
hl_cb_put(cb) is called, to avoid the potential uaf.

The Linux kernel CVE team has assigned CVE-2021-47081 to this issue.

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

	Issue introduced in 5.12 with commit 423815bf02e2 and fixed in 5.12.7 with commit b49f5af30b0e
	Issue introduced in 5.12 with commit 423815bf02e2 and fixed in 5.13 with commit 115726c5d312

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-2021-47081
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/misc/habanalabs/gaudi/gaudi.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/b49f5af30b0e4064fbd91e83823a4bfcb2c7a3e7
	https://git.kernel.org/stable/c/115726c5d312b462c9d9931ea42becdfa838a076