Subject: CVE-2024-36916: blk-iocost: avoid out of bounds shift

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

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

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

blk-iocost: avoid out of bounds shift

UBSAN catches undefined behavior in blk-iocost, where sometimes
iocg->delay is shifted right by a number that is too large,
resulting in undefined behavior on some architectures.

[  186.556576] ------------[ cut here ]------------
UBSAN: shift-out-of-bounds in block/blk-iocost.c:1366:23
shift exponent 64 is too large for 64-bit type 'u64' (aka 'unsigned long long')
CPU: 16 PID: 0 Comm: swapper/16 Tainted: G S          E    N 6.9.0-0_fbk700_debug_rc2_kbuilder_0_gc85af715cac0 #1
Hardware name: Quanta Twin Lakes MP/Twin Lakes Passive MP, BIOS F09_3A23 12/08/2020
Call Trace:
 <IRQ>
 dump_stack_lvl+0x8f/0xe0
 __ubsan_handle_shift_out_of_bounds+0x22c/0x280
 iocg_kick_delay+0x30b/0x310
 ioc_timer_fn+0x2fb/0x1f80
 __run_timer_base+0x1b6/0x250
...

Avoid that undefined behavior by simply taking the
"delay = 0" branch if the shift is too large.

I am not sure what the symptoms of an undefined value
delay will be, but I suspect it could be more than a
little annoying to debug.

The Linux kernel CVE team has assigned CVE-2024-36916 to this issue.

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

	Fixed in 5.10.217 with commit 62accf6c1d7b
	Fixed in 5.15.159 with commit 844fc023e9f1
	Fixed in 6.1.91 with commit f6add0a6f78d
	Fixed in 6.6.31 with commit ce0e99cae00e
	Fixed in 6.8.10 with commit 488dc6808cb8
	Fixed in 6.9 with commit beaa51b36012

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-2024-36916
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:
	block/blk-iocost.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/62accf6c1d7b433752cb3591bba8967b7a801ad5
	https://git.kernel.org/stable/c/844fc023e9f14a4fb1de5ae1eaefafd6d69c5fa1
	https://git.kernel.org/stable/c/f6add0a6f78dc6360b822ca4b6f9f2f14174c8ca
	https://git.kernel.org/stable/c/ce0e99cae00e3131872936713b7f55eefd53ab86
	https://git.kernel.org/stable/c/488dc6808cb8369685f18cee81e88e7052ac153b
	https://git.kernel.org/stable/c/beaa51b36012fad5a4d3c18b88a617aea7a9b96d