This is a note to let you know that I've just added the patch titled
blktrace: fix unlocked registration of tracepoints
to the 4.4-stable tree which can be found at: http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git%3Ba=su...
The filename of the patch is: blktrace-fix-unlocked-registration-of-tracepoints.patch and it can be found in the queue-4.4 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree, please let stable@vger.kernel.org know about it.
From a6da0024ffc19e0d47712bb5ca4fd083f76b07df Mon Sep 17 00:00:00 2001
From: Jens Axboe axboe@kernel.dk Date: Sun, 5 Nov 2017 09:16:09 -0700 Subject: blktrace: fix unlocked registration of tracepoints
From: Jens Axboe axboe@kernel.dk
commit a6da0024ffc19e0d47712bb5ca4fd083f76b07df upstream.
We need to ensure that tracepoints are registered and unregistered with the users of them. The existing atomic count isn't enough for that. Add a lock around the tracepoints, so we serialize access to them.
This fixes cases where we have multiple users setting up and tearing down tracepoints, like this:
CPU: 0 PID: 2995 Comm: syzkaller857118 Not tainted 4.14.0-rc5-next-20171018+ #36 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 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_add_func kernel/tracepoint.c:210 [inline] RIP: 0010:tracepoint_probe_register_prio+0x397/0x9a0 kernel/tracepoint.c:283 RSP: 0018:ffff8801d1d1f6c0 EFLAGS: 00010293 RAX: ffff8801d22e8540 RBX: 00000000ffffffef RCX: ffffffff81710f07 RDX: 0000000000000000 RSI: ffffffff85b679c0 RDI: ffff8801d5f19818 RBP: ffff8801d1d1f7c8 R08: ffffffff81710c10 R09: 0000000000000004 R10: ffff8801d1d1f6b0 R11: 0000000000000003 R12: ffffffff817597f0 R13: 0000000000000000 R14: 00000000ffffffff R15: ffff8801d1d1f7a0 tracepoint_probe_register+0x2a/0x40 kernel/tracepoint.c:304 register_trace_block_rq_insert include/trace/events/block.h:191 [inline] blk_register_tracepoints+0x1e/0x2f0 kernel/trace/blktrace.c:1043 do_blk_trace_setup+0xa10/0xcf0 kernel/trace/blktrace.c:542 blk_trace_setup+0xbd/0x180 kernel/trace/blktrace.c:564 sg_ioctl+0xc71/0x2d90 drivers/scsi/sg.c:1089 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: 0033:0x444339 RSP: 002b:00007ffe05bb5b18 EFLAGS: 00000206 ORIG_RAX: 0000000000000010 RAX: ffffffffffffffda RBX: 00000000006d66c0 RCX: 0000000000444339 RDX: 000000002084cf90 RSI: 00000000c0481273 RDI: 0000000000000009 RBP: 0000000000000082 R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000206 R12: ffffffffffffffff R13: 00000000c0481273 R14: 0000000000000000 R15: 0000000000000000
since we can now run these in parallel. Ensure that the exported helpers for doing this are grabbing the queue trace mutex.
Reported-by: Steven Rostedt rostedt@goodmis.org Tested-by: Dmitry Vyukov dvyukov@google.com Signed-off-by: Jens Axboe axboe@kernel.dk Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org
--- kernel/trace/blktrace.c | 32 ++++++++++++++++++++++---------- 1 file changed, 22 insertions(+), 10 deletions(-)
--- a/kernel/trace/blktrace.c +++ b/kernel/trace/blktrace.c @@ -57,7 +57,8 @@ static struct tracer_flags blk_tracer_fl };
/* 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); @@ -300,11 +301,26 @@ static void blk_trace_free(struct blk_tr 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) @@ -522,8 +538,7 @@ int do_blk_trace_setup(struct request_qu if (cmpxchg(&q->blk_trace, NULL, bt)) goto err;
- if (atomic_inc_return(&blk_probes_ref) == 1) - blk_register_tracepoints(); + get_probe_ref();
return 0; err: @@ -1466,9 +1481,7 @@ static int blk_trace_remove_queue(struct 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; } @@ -1499,8 +1512,7 @@ static int blk_trace_setup_queue(struct 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:
Patches currently in stable-queue which might be from axboe@kernel.dk are
queue-4.4/blktrace-fix-unlocked-registration-of-tracepoints.patch