[PATCH 5.10 011/199] crypto: xor - Fix divide error in do_xor_speed()

Greg Kroah-Hartman
2021-01-26T09:13:34Z

From: Kirill Tkhai <ktkhai@virtuozzo.com>

commit 3c02e04fd4f57130e4fa75fab6f528f7a52db9b5 upstream.

crypto: Fix divide error in do_xor_speed()

From: Kirill Tkhai <ktkhai@virtuozzo.com>

Latest (but not only latest) linux-next panics with divide
error on my QEMU setup.

The patch at the bottom of this message fixes the problem.

xor: measuring software checksum speed
divide error: 0000 [#1] PREEMPT SMP KASAN
PREEMPT SMP KASAN
CPU: 3 PID: 1 Comm: swapper/0 Not tainted 5.10.0-next-20201223+ #2177
RIP: 0010:do_xor_speed+0xbb/0xf3
Code: 41 ff cc 75 b5 bf 01 00 00 00 e8 3d 23 8b fe 65 8b 05 f6 49 83 7d 85 c0 75 05 e8
84 70 81 fe b8 00 00 50 c3 31 d2 48 8d 7b 10 <f7> f5 41 89 c4 e8 58 07 a2 fe 44 89 63 10 48 8d 7b 08
e8 cb 07 a2
RSP: 0000:ffff888100137dc8 EFLAGS: 00010246
RAX: 00000000c3500000 RBX: ffffffff823f0160 RCX: 0000000000000000
RDX: 0000000000000000 RSI: 0000000000000808 RDI: ffffffff823f0170
RBP: 0000000000000000 R08: ffffffff8109c50f R09: ffffffff824bb6f7
R10: fffffbfff04976de R11: 0000000000000001 R12: 0000000000000000
R13: ffff888101997000 R14: ffff888101994000 R15: ffffffff823f0178
FS: 0000000000000000(0000) GS:ffff8881f7780000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000000000000000 CR3: 000000000220e000 CR4: 00000000000006a0
Call Trace:
calibrate_xor_blocks+0x13c/0x1c4
? do_xor_speed+0xf3/0xf3
do_one_initcall+0xc1/0x1b7
? start_kernel+0x373/0x373
? unpoison_range+0x3a/0x60
kernel_init_freeable+0x1dd/0x238
? rest_init+0xc6/0xc6
kernel_init+0x8/0x10a
ret_from_fork+0x1f/0x30
---[ end trace 5bd3c1d0b77772da ]---

Fixes: c055e3eae0f1 ("crypto: xor - use ktime for template benchmarking")
Cc: <stable@vger.kernel.org>
Signed-off-by: Kirill Tkhai <ktkhai@virtuozzo.com>
Acked-by: Ard Biesheuvel <ardb@kernel.org>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
crypto/xor.c | 2 ++
1 file changed, 2 insertions(+)

--- a/crypto/xor.c
+++ b/crypto/xor.c
@@ -107,6 +107,8 @@ do_xor_speed(struct xor_block_template *
preempt_enable();

// bytes/ns == GB/s, multiply by 1000 to get MB/s [not MiB/s]
+ if (!min)
+ min = 1;
speed = (1000 * REPS * BENCH_SIZE) / (unsigned int)ktime_to_ns(min);
tmpl->speed = speed;