From: Jiri Olsa <jolsa@kernel.org>
To: "Theodore Ts'o" <tytso@mit.edu>
Cc: "H. Peter Anvin" <hpa@zytor.com>, Greg Price <price@mit.edu>,
lkml <linux-kernel@vger.kernel.org>
Subject: [PATCH] random: Fix early crash in credit_entropy_bits
Date: Wed, 21 Sep 2016 17:07:11 +0200 [thread overview]
Message-ID: <1474470431-27532-1-git-send-email-jolsa@kernel.org> (raw)
From: Jiri Olsa <jolsa@redhat.com>
When printing out some early acpi messages I hit bug in
work queue code. The system_wq is not initialized at the
time acpi_early_init is called and causes irq storm that
makes credit_entropy_bits call schedule_work and crash:
BUG: unable to handle kernel NULL pointer dereference at 0000000000000102^M
IP: [<ffffffff810bc282>] __queue_work+0x32/0x450^M
PGD 0 ^M
Oops: 0000 [#1] SMP^M
...
Call Trace:^M
<IRQ> [ 286.521689] [<ffffffff817b5dc6>] ? _raw_write_unlock_irqrestore+0x16/0x20^M
[<ffffffff814f0f82>] ? add_interrupt_randomness+0x1c2/0x200^M
[<ffffffff810bcc47>] queue_work_on+0x27/0x40^M
[<ffffffff814f03a9>] credit_entropy_bits+0x219/0x280^M
[<ffffffff814ee4f6>] ? __mix_pool_bytes+0x36/0x90^M
[<ffffffff814f0f82>] add_interrupt_randomness+0x1c2/0x200^M
[<ffffffff810fe570>] handle_irq_event_percpu+0x40/0x80^M
[<ffffffff810fe5dc>] handle_irq_event+0x2c/0x50^M
[<ffffffff81101b93>] handle_level_irq+0x83/0x100^M
[<ffffffff8102fdb3>] handle_irq+0x73/0x120^M
[<ffffffff810a8fa1>] ? _local_bh_enable+0x21/0x50^M
[<ffffffff817b8d2b>] do_IRQ+0x4b/0xd0^M
[<ffffffff817b6bcc>] common_interrupt+0x8c/0x8c^M
<EOI> [ 286.521717] [<ffffffff81062216>] ? native_restore_fl+0x6/0x10^M
[<ffffffff810fbb4f>] console_unlock+0x3ef/0x5d0^M
[<ffffffff8100dade>] ? update_sample+0x6e/0xe0^M
[<ffffffff810fc55a>] vprintk_emit+0x2aa/0x520^M
[<ffffffff810fc96f>] vprintk_default+0x1f/0x30^M
[<ffffffff811a87b9>] printk+0x57/0x73^M
[<ffffffff81447dda>] acpi_os_vprintf+0x3f/0x41^M
[<ffffffff81447e2e>] acpi_os_printf+0x52/0x6e^M
...
[<ffffffff81dbfc56>] acpi_load_tables+0x6c/0xf4^M
[<ffffffff81dbe4a6>] acpi_early_init+0x7a/0xf0^M
[<ffffffff81d73f39>] start_kernel+0x3be/0x472^M
Preventing this by checking the system_wq has been initialized already.
Signed-off-by: Jiri Olsa <jolsa@kernel.org>
---
drivers/char/random.c | 3 ++-
1 file changed, 2 insertions(+), 1 deletion(-)
diff --git a/drivers/char/random.c b/drivers/char/random.c
index 3efb3bf0ab83..f4dec86c2e25 100644
--- a/drivers/char/random.c
+++ b/drivers/char/random.c
@@ -725,7 +725,8 @@ retry:
/* If the input pool is getting full, send some
* entropy to the blocking pool until it is 75% full.
*/
- if (entropy_bits > random_write_wakeup_bits &&
+ if (keventd_up() &&
+ entropy_bits > random_write_wakeup_bits &&
r->initialized &&
r->entropy_total >= 2*random_read_wakeup_bits) {
struct entropy_store *other = &blocking_pool;
--
2.7.4
next reply other threads:[~2016-09-21 15:07 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-09-21 15:07 Jiri Olsa [this message]
2016-10-05 19:07 ` [PATCH] random: Fix early crash in credit_entropy_bits Jiri Olsa
2016-10-05 20:27 ` Theodore Ts'o
2016-10-06 13:24 ` Jiri Olsa
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