This is a note to let you know that I've just added the patch titled
hpet: Fix division by zero in hpet_time_div()
to my char-misc git tree which can be found at
git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/char-misc.git
in the char-misc-linus branch.
The patch will show up in the next release of the linux-next tree
(usually sometime within the next 24 hours during the week.)
The patch will hopefully also be merged in Linus's tree for the
next -rc kernel release.
If you have any questions about this process, please let me know.
>From 0c7d37f4d9b8446956e97b7c5e61173cdb7c8522 Mon Sep 17 00:00:00 2001
From: Kefeng Wang <wangkefeng.wang@xxxxxxxxxx>
Date: Thu, 11 Jul 2019 21:27:57 +0800
Subject: hpet: Fix division by zero in hpet_time_div()
The base value in do_div() called by hpet_time_div() is truncated from
unsigned long to uint32_t, resulting in a divide-by-zero exception.
UBSAN: Undefined behaviour in ../drivers/char/hpet.c:572:2
division by zero
CPU: 1 PID: 23682 Comm: syz-executor.3 Not tainted 4.4.184.x86_64+ #4
Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS Ubuntu-1.8.2-1ubuntu1 04/01/2014
0000000000000000 b573382df1853d00 ffff8800a3287b98 ffffffff81ad7561
ffff8800a3287c00 ffffffff838b35b0 ffffffff838b3860 ffff8800a3287c20
0000000000000000 ffff8800a3287bb0 ffffffff81b8f25e ffffffff838b35a0
Call Trace:
[<ffffffff81ad7561>] __dump_stack lib/dump_stack.c:15 [inline]
[<ffffffff81ad7561>] dump_stack+0xc1/0x120 lib/dump_stack.c:51
[<ffffffff81b8f25e>] ubsan_epilogue+0x12/0x8d lib/ubsan.c:166
[<ffffffff81b900cb>] __ubsan_handle_divrem_overflow+0x282/0x2c8 lib/ubsan.c:262
[<ffffffff823560dd>] hpet_time_div drivers/char/hpet.c:572 [inline]
[<ffffffff823560dd>] hpet_ioctl_common drivers/char/hpet.c:663 [inline]
[<ffffffff823560dd>] hpet_ioctl_common.cold+0xa8/0xad drivers/char/hpet.c:577
[<ffffffff81e63d56>] hpet_ioctl+0xc6/0x180 drivers/char/hpet.c:676
[<ffffffff81711590>] vfs_ioctl fs/ioctl.c:43 [inline]
[<ffffffff81711590>] file_ioctl fs/ioctl.c:470 [inline]
[<ffffffff81711590>] do_vfs_ioctl+0x6e0/0xf70 fs/ioctl.c:605
[<ffffffff81711eb4>] SYSC_ioctl fs/ioctl.c:622 [inline]
[<ffffffff81711eb4>] SyS_ioctl+0x94/0xc0 fs/ioctl.c:613
[<ffffffff82846003>] tracesys_phase2+0x90/0x95
The main C reproducer autogenerated by syzkaller,
syscall(__NR_mmap, 0x20000000, 0x1000000, 3, 0x32, -1, 0);
memcpy((void*)0x20000100, "/dev/hpet\000", 10);
syscall(__NR_openat, 0xffffffffffffff9c, 0x20000100, 0, 0);
syscall(__NR_ioctl, r[0], 0x40086806, 0x40000000000000);
Fix it by using div64_ul().
Signed-off-by: Kefeng Wang <wangkefeng.wang@xxxxxxxxxx>
Signed-off-by: Zhang HongJun <zhanghongjun2@xxxxxxxxxx>
Cc: stable <stable@xxxxxxxxxxxxxxx>
Reviewed-by: Arnd Bergmann <arnd@xxxxxxxx>
Link: https://lore.kernel.org/r/20190711132757.130092-1-wangkefeng.wang@xxxxxxxxxx
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
drivers/char/hpet.c | 3 +--
1 file changed, 1 insertion(+), 2 deletions(-)
diff --git a/drivers/char/hpet.c b/drivers/char/hpet.c
index 5c39f20378b8..9ac6671bb514 100644
--- a/drivers/char/hpet.c
+++ b/drivers/char/hpet.c
@@ -567,8 +567,7 @@ static inline unsigned long hpet_time_div(struct hpets *hpets,
unsigned long long m;
m = hpets->hp_tick_freq + (dis >> 1);
- do_div(m, dis);
- return (unsigned long)m;
+ return div64_ul(m, dis);
}
static int
--
2.22.0
