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Date: Sun, 5 Nov 2017 08:47:14 -0700
From: Jens Axboe <axboe@...nel.dk>
To: Dmitry Vyukov <dvyukov@...gle.com>,
syzbot
<bot+f00b2fc1cf284703bf4107c0ea565aafd9b536d0@...kaller.appspotmail.com>,
Steven Rostedt <rostedt@...dmis.org>,
Mathieu Desnoyers <mathieu.desnoyers@...icios.com>
Cc: LKML <linux-kernel@...r.kernel.org>,
Ingo Molnar <mingo@...nel.org>, syzkaller-bugs@...glegroups.com
Subject: Re: WARNING in tracepoint_probe_unregister
On 11/05/2017 01:09 AM, Dmitry Vyukov wrote:
> On Sun, Nov 5, 2017 at 11:05 AM, syzbot
> <bot+f00b2fc1cf284703bf4107c0ea565aafd9b536d0@...kaller.appspotmail.com>
> wrote:
>> Hello,
>>
>> syzkaller hit the following crash on
>> 36ef71cae353f88fd6e095e2aaa3e5953af1685d
>> git://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git/master
>> compiler: gcc (GCC) 7.1.1 20170620
>> .config is attached
>> Raw console output is attached.
>> C reproducer is attached
>> syzkaller reproducer is attached. See https://goo.gl/kgGztJ
>> for information about syzkaller reproducers
>>
>>
>> WARNING: CPU: 1 PID: 2992 at kernel/tracepoint.c:243 tracepoint_remove_func
>> kernel/tracepoint.c:243 [inline]
>> WARNING: CPU: 1 PID: 2992 at kernel/tracepoint.c:243
>> tracepoint_probe_unregister+0x6b3/0x870 kernel/tracepoint.c:324
>> Kernel panic - not syncing: panic_on_warn set ...
>>
>> CPU: 1 PID: 2992 Comm: syzkaller812809 Not tainted 4.14.0-rc5-next-20171018+
>> #8
>> Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS Bochs 01/01/2011
>> Call Trace:
>> __dump_stack lib/dump_stack.c:16 [inline]
>> dump_stack+0x194/0x257 lib/dump_stack.c:52
>> panic+0x1e4/0x41c kernel/panic.c:183
>> __warn+0x1c4/0x1e0 kernel/panic.c:546
>> report_bug+0x211/0x2d0 lib/bug.c:183
>> fixup_bug+0x40/0x90 arch/x86/kernel/traps.c:177
>> do_trap_no_signal arch/x86/kernel/traps.c:211 [inline]
>> do_trap+0x260/0x390 arch/x86/kernel/traps.c:260
>> do_error_trap+0x120/0x390 arch/x86/kernel/traps.c:297
>> do_invalid_op+0x1b/0x20 arch/x86/kernel/traps.c:310
>> invalid_op+0x18/0x20 arch/x86/entry/entry_64.S:905
>> RIP: 0010:tracepoint_remove_func kernel/tracepoint.c:243 [inline]
>> RIP: 0010:tracepoint_probe_unregister+0x6b3/0x870 kernel/tracepoint.c:324
>> RSP: 0018:ffff8800397df890 EFLAGS: 00010293
>> RAX: ffff88003982e8c0 RBX: 00000000fffffffe RCX: ffffffff81710233
>> RDX: 0000000000000000 RSI: ffffffff85b679c0 RDI: 0000000000000282
>> RBP: ffff8800397df9a8 R08: 0000000000000001 R09: 1ffff100072fbe6e
>> R10: ffff8800397df880 R11: 0000000000000001 R12: ffffffff8175b5e0
>> R13: dffffc0000000000 R14: 0000000000000000 R15: ffff8800397df980
>> unregister_trace_block_rq_remap include/trace/events/block.h:602 [inline]
>> blk_unregister_tracepoints+0x1e/0x160 kernel/trace/blktrace.c:1079
>> blk_trace_cleanup+0x28/0x30 kernel/trace/blktrace.c:336
>> blk_trace_remove+0x55/0x80 kernel/trace/blktrace.c:348
>> sg_ioctl+0x5eb/0x2d90 drivers/scsi/sg.c:1098
>> vfs_ioctl fs/ioctl.c:45 [inline]
>> do_vfs_ioctl+0x1b1/0x1520 fs/ioctl.c:685
>> SYSC_ioctl fs/ioctl.c:700 [inline]
>> SyS_ioctl+0x8f/0xc0 fs/ioctl.c:691
>> entry_SYSCALL_64_fastpath+0x1f/0xbe
>> RIP: 0033:0x4396a9
>> RSP: 002b:00007ffd4d3facb8 EFLAGS: 00000206 ORIG_RAX: 0000000000000010
>> RAX: ffffffffffffffda RBX: 00000000006ccac0 RCX: 00000000004396a9
>> RDX: 000000002002d000 RSI: 4000000000001276 RDI: 0000000000000004
>> RBP: 0000000000000082 R08: 00000000000000fe R09: 0000000000000000
>> R10: 0000000000000000 R11: 0000000000000206 R12: 0000000000000038
>> R13: ffffffffffffffff R14: 0000000000401eb0 R15: 0000000000000000
>> Dumping ftrace buffer:
>> (ftrace buffer empty)
>> Kernel Offset: disabled
>> Rebooting in 86400 seconds..
>
>
> Jens, this has the same root cause as "WARNING in
> tracepoint_probe_register_prio":
> https://groups.google.com/forum/#!msg/syzkaller-bugs/9IolqTA_NUk/LgLFZ6hQAQAJ
> right?
Yep, it is - can/did you check the patch I sent out yesterday for this?
Here it is again.
diff --git a/kernel/trace/blktrace.c b/kernel/trace/blktrace.c
index 45a3928544ce..206e0e2ace53 100644
--- a/kernel/trace/blktrace.c
+++ b/kernel/trace/blktrace.c
@@ -66,7 +66,8 @@ static struct tracer_flags blk_tracer_flags = {
};
/* Global reference count of probes */
-static atomic_t blk_probes_ref = ATOMIC_INIT(0);
+static DEFINE_MUTEX(blk_probe_mutex);
+static int blk_probes_ref;
static void blk_register_tracepoints(void);
static void blk_unregister_tracepoints(void);
@@ -329,14 +330,29 @@ static void blk_trace_free(struct blk_trace *bt)
kfree(bt);
}
+static void get_probe_ref(void)
+{
+ mutex_lock(&blk_probe_mutex);
+ if (++blk_probes_ref == 1)
+ blk_register_tracepoints();
+ mutex_unlock(&blk_probe_mutex);
+}
+
+static void put_probe_ref(void)
+{
+ mutex_lock(&blk_probe_mutex);
+ if (!--blk_probes_ref)
+ blk_unregister_tracepoints();
+ mutex_unlock(&blk_probe_mutex);
+}
+
static void blk_trace_cleanup(struct blk_trace *bt)
{
blk_trace_free(bt);
- if (atomic_dec_and_test(&blk_probes_ref))
- blk_unregister_tracepoints();
+ put_probe_ref();
}
-int blk_trace_remove(struct request_queue *q)
+static int __blk_trace_remove(struct request_queue *q)
{
struct blk_trace *bt;
@@ -349,6 +365,17 @@ int blk_trace_remove(struct request_queue *q)
return 0;
}
+
+int blk_trace_remove(struct request_queue *q)
+{
+ int ret;
+
+ mutex_lock(&q->blk_trace_mutex);
+ ret = __blk_trace_remove(q);
+ mutex_unlock(&q->blk_trace_mutex);
+
+ return ret;
+}
EXPORT_SYMBOL_GPL(blk_trace_remove);
static ssize_t blk_dropped_read(struct file *filp, char __user *buffer,
@@ -538,8 +565,7 @@ static int do_blk_trace_setup(struct request_queue *q, char *name, dev_t dev,
if (cmpxchg(&q->blk_trace, NULL, bt))
goto err;
- if (atomic_inc_return(&blk_probes_ref) == 1)
- blk_register_tracepoints();
+ get_probe_ref();
ret = 0;
err:
@@ -550,9 +576,8 @@ static int do_blk_trace_setup(struct request_queue *q, char *name, dev_t dev,
return ret;
}
-int blk_trace_setup(struct request_queue *q, char *name, dev_t dev,
- struct block_device *bdev,
- char __user *arg)
+static int __blk_trace_setup(struct request_queue *q, char *name, dev_t dev,
+ struct block_device *bdev, char __user *arg)
{
struct blk_user_trace_setup buts;
int ret;
@@ -571,6 +596,19 @@ int blk_trace_setup(struct request_queue *q, char *name, dev_t dev,
}
return 0;
}
+
+int blk_trace_setup(struct request_queue *q, char *name, dev_t dev,
+ struct block_device *bdev,
+ char __user *arg)
+{
+ int ret;
+
+ mutex_lock(&q->blk_trace_mutex);
+ ret = __blk_trace_setup(q, name, dev, bdev, arg);
+ mutex_unlock(&q->blk_trace_mutex);
+
+ return ret;
+}
EXPORT_SYMBOL_GPL(blk_trace_setup);
#if defined(CONFIG_COMPAT) && defined(CONFIG_X86_64)
@@ -607,7 +645,7 @@ static int compat_blk_trace_setup(struct request_queue *q, char *name,
}
#endif
-int blk_trace_startstop(struct request_queue *q, int start)
+static int __blk_trace_startstop(struct request_queue *q, int start)
{
int ret;
struct blk_trace *bt = q->blk_trace;
@@ -646,6 +684,17 @@ int blk_trace_startstop(struct request_queue *q, int start)
return ret;
}
+
+int blk_trace_startstop(struct request_queue *q, int start)
+{
+ int ret;
+
+ mutex_lock(&q->blk_trace_mutex);
+ ret = __blk_trace_startstop(q, start);
+ mutex_unlock(&q->blk_trace_mutex);
+
+ return ret;
+}
EXPORT_SYMBOL_GPL(blk_trace_startstop);
/*
@@ -676,7 +725,7 @@ int blk_trace_ioctl(struct block_device *bdev, unsigned cmd, char __user *arg)
switch (cmd) {
case BLKTRACESETUP:
bdevname(bdev, b);
- ret = blk_trace_setup(q, b, bdev->bd_dev, bdev, arg);
+ ret = __blk_trace_setup(q, b, bdev->bd_dev, bdev, arg);
break;
#if defined(CONFIG_COMPAT) && defined(CONFIG_X86_64)
case BLKTRACESETUP32:
@@ -687,10 +736,10 @@ int blk_trace_ioctl(struct block_device *bdev, unsigned cmd, char __user *arg)
case BLKTRACESTART:
start = 1;
case BLKTRACESTOP:
- ret = blk_trace_startstop(q, start);
+ ret = __blk_trace_startstop(q, start);
break;
case BLKTRACETEARDOWN:
- ret = blk_trace_remove(q);
+ ret = __blk_trace_remove(q);
break;
default:
ret = -ENOTTY;
@@ -708,10 +757,14 @@ int blk_trace_ioctl(struct block_device *bdev, unsigned cmd, char __user *arg)
**/
void blk_trace_shutdown(struct request_queue *q)
{
+ mutex_lock(&q->blk_trace_mutex);
+
if (q->blk_trace) {
- blk_trace_startstop(q, 0);
- blk_trace_remove(q);
+ __blk_trace_startstop(q, 0);
+ __blk_trace_remove(q);
}
+
+ mutex_unlock(&q->blk_trace_mutex);
}
#ifdef CONFIG_BLK_CGROUP
@@ -1558,9 +1611,7 @@ static int blk_trace_remove_queue(struct request_queue *q)
if (bt == NULL)
return -EINVAL;
- if (atomic_dec_and_test(&blk_probes_ref))
- blk_unregister_tracepoints();
-
+ put_probe_ref();
blk_trace_free(bt);
return 0;
}
@@ -1591,8 +1642,7 @@ static int blk_trace_setup_queue(struct request_queue *q,
if (cmpxchg(&q->blk_trace, NULL, bt))
goto free_bt;
- if (atomic_inc_return(&blk_probes_ref) == 1)
- blk_register_tracepoints();
+ get_probe_ref();
return 0;
free_bt:
--
Jens Axboe
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