Commit 3d1c1055 authored by Konstantin Ovsepian's avatar Konstantin Ovsepian Committed by Zheng Qixing
Browse files

blk_iocost: fix more out of bound shifts 

stable inclusion
from stable-v5.10.227
commit 1f61d509257d6a05763d05bf37943b35306522b1
category: bugfix
bugzilla: https://gitee.com/src-openeuler/kernel/issues/IAYRCW
CVE: CVE-2024-49933

Reference: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=1f61d509257d6a05763d05bf37943b35306522b1



--------------------------------

[ Upstream commit 9bce8005ec0dcb23a58300e8522fe4a31da606fa ]

Recently running UBSAN caught few out of bound shifts in the
ioc_forgive_debts() function:

UBSAN: shift-out-of-bounds in block/blk-iocost.c:2142:38
shift exponent 80 is too large for 64-bit type 'u64' (aka 'unsigned long
long')
...
UBSAN: shift-out-of-bounds in block/blk-iocost.c:2144:30
shift exponent 80 is too large for 64-bit type 'u64' (aka 'unsigned long
long')
...
Call Trace:
<IRQ>
dump_stack_lvl+0xca/0x130
__ubsan_handle_shift_out_of_bounds+0x22c/0x280
? __lock_acquire+0x6441/0x7c10
ioc_timer_fn+0x6cec/0x7750
? blk_iocost_init+0x720/0x720
? call_timer_fn+0x5d/0x470
call_timer_fn+0xfa/0x470
? blk_iocost_init+0x720/0x720
__run_timer_base+0x519/0x700
...

Actual impact of this issue was not identified but I propose to fix the
undefined behaviour.
The proposed fix to prevent those out of bound shifts consist of
precalculating exponent before using it the shift operations by taking
min value from the actual exponent and maximum possible number of bits.

Reported-by: default avatarBreno Leitao <leitao@debian.org>
Signed-off-by: default avatarKonstantin Ovsepian <ovs@ovs.to>
Acked-by: default avatarTejun Heo <tj@kernel.org>
Link: https://lore.kernel.org/r/20240822154137.2627818-1-ovs@ovs.to


Signed-off-by: default avatarJens Axboe <axboe@kernel.dk>
Signed-off-by: default avatarSasha Levin <sashal@kernel.org>
Signed-off-by: default avatarZheng Qixing <zhengqixing@huawei.com>
parent 8dcdd5a4

block/blk-iocost.c

+5 −3
Original line number Diff line number Diff line
@@ -2047,7 +2047,7 @@ static void ioc_forgive_debts(struct ioc *ioc, u64 usage_us_sum, int nr_debtors, 
			      struct ioc_now *now)

{

	struct ioc_gq *iocg;

	u64 dur, usage_pct, nr_cycles;

	u64 dur, usage_pct, nr_cycles, nr_cycles_shift;



	/* if no debtor, reset the cycle */

	if (!nr_debtors) {
@@ -2109,10 +2109,12 @@ static void ioc_forgive_debts(struct ioc *ioc, u64 usage_us_sum, int nr_debtors, 
		old_debt = iocg->abs_vdebt;

		old_delay = iocg->delay;



		nr_cycles_shift = min_t(u64, nr_cycles, BITS_PER_LONG - 1);

		if (iocg->abs_vdebt)

			iocg->abs_vdebt = iocg->abs_vdebt >> nr_cycles ?: 1;

			iocg->abs_vdebt = iocg->abs_vdebt >> nr_cycles_shift ?: 1;



		if (iocg->delay)

			iocg->delay = iocg->delay >> nr_cycles ?: 1;

			iocg->delay = iocg->delay >> nr_cycles_shift ?: 1;



		iocg_kick_waitq(iocg, true, now);