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* KASAN: use-after-free Read in addr_handler (2)
@ 2020-06-10 17:02 syzbot
       [not found] ` <20200614085321.8740-1-hdanton@sina.com>
  0 siblings, 1 reply; 8+ messages in thread
From: syzbot @ 2020-06-10 17:02 UTC (permalink / raw)
  To: chuck.lever, dledford, jgg, leon, linux-kernel, linux-rdma,
	parav, syzkaller-bugs

Hello,

syzbot found the following crash on:

HEAD commit:    7ae77150 Merge tag 'powerpc-5.8-1' of git://git.kernel.org..
git tree:       upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=16c0d3a6100000
kernel config:  https://syzkaller.appspot.com/x/.config?x=d195fe572fb15312
dashboard link: https://syzkaller.appspot.com/bug?extid=a929647172775e335941
compiler:       gcc (GCC) 9.0.0 20181231 (experimental)

Unfortunately, I don't have any reproducer for this crash yet.

IMPORTANT: if you fix the bug, please add the following tag to the commit:
Reported-by: syzbot+a929647172775e335941@syzkaller.appspotmail.com

==================================================================
BUG: KASAN: use-after-free in __mutex_lock_common kernel/locking/mutex.c:938 [inline]
BUG: KASAN: use-after-free in __mutex_lock+0x1033/0x13c0 kernel/locking/mutex.c:1103
Read of size 8 at addr ffff888088ec33b0 by task kworker/u4:5/14014

CPU: 1 PID: 14014 Comm: kworker/u4:5 Not tainted 5.7.0-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
Workqueue: ib_addr process_one_req
Call Trace:
 __dump_stack lib/dump_stack.c:77 [inline]
 dump_stack+0x188/0x20d lib/dump_stack.c:118
 print_address_description.constprop.0.cold+0xd3/0x413 mm/kasan/report.c:383
 __kasan_report mm/kasan/report.c:513 [inline]
 kasan_report.cold+0x1f/0x37 mm/kasan/report.c:530
 __mutex_lock_common kernel/locking/mutex.c:938 [inline]
 __mutex_lock+0x1033/0x13c0 kernel/locking/mutex.c:1103
 addr_handler+0xa0/0x340 drivers/infiniband/core/cma.c:3100
 process_one_req+0xfa/0x680 drivers/infiniband/core/addr.c:643
 process_one_work+0x965/0x16a0 kernel/workqueue.c:2268
 worker_thread+0x96/0xe20 kernel/workqueue.c:2414
 kthread+0x388/0x470 kernel/kthread.c:268
 ret_from_fork+0x24/0x30 arch/x86/entry/entry_64.S:351

Allocated by task 31499:
 save_stack+0x1b/0x40 mm/kasan/common.c:48
 set_track mm/kasan/common.c:56 [inline]
 __kasan_kmalloc mm/kasan/common.c:494 [inline]
 __kasan_kmalloc.constprop.0+0xbf/0xd0 mm/kasan/common.c:467
 kmem_cache_alloc_trace+0x153/0x7d0 mm/slab.c:3551
 kmalloc include/linux/slab.h:555 [inline]
 kzalloc include/linux/slab.h:669 [inline]
 __rdma_create_id+0x5b/0x850 drivers/infiniband/core/cma.c:861
 ucma_create_id+0x1d1/0x590 drivers/infiniband/core/ucma.c:503
 ucma_write+0x285/0x350 drivers/infiniband/core/ucma.c:1729
 __vfs_write+0x76/0x100 fs/read_write.c:495
 vfs_write+0x268/0x5d0 fs/read_write.c:559
 ksys_write+0x1ee/0x250 fs/read_write.c:612
 do_syscall_64+0xf6/0x7d0 arch/x86/entry/common.c:295
 entry_SYSCALL_64_after_hwframe+0x49/0xb3

Freed by task 31496:
 save_stack+0x1b/0x40 mm/kasan/common.c:48
 set_track mm/kasan/common.c:56 [inline]
 kasan_set_free_info mm/kasan/common.c:316 [inline]
 __kasan_slab_free+0xf7/0x140 mm/kasan/common.c:455
 __cache_free mm/slab.c:3426 [inline]
 kfree+0x109/0x2b0 mm/slab.c:3757
 ucma_close+0x111/0x300 drivers/infiniband/core/ucma.c:1807
 __fput+0x33e/0x880 fs/file_table.c:281
 task_work_run+0xf4/0x1b0 kernel/task_work.c:123
 tracehook_notify_resume include/linux/tracehook.h:188 [inline]
 exit_to_usermode_loop+0x2fa/0x360 arch/x86/entry/common.c:165
 prepare_exit_to_usermode arch/x86/entry/common.c:196 [inline]
 syscall_return_slowpath arch/x86/entry/common.c:279 [inline]
 do_syscall_64+0x6b1/0x7d0 arch/x86/entry/common.c:305
 entry_SYSCALL_64_after_hwframe+0x49/0xb3

The buggy address belongs to the object at ffff888088ec3000
 which belongs to the cache kmalloc-2k of size 2048
The buggy address is located 944 bytes inside of
 2048-byte region [ffff888088ec3000, ffff888088ec3800)
The buggy address belongs to the page:
page:ffffea000223b0c0 refcount:1 mapcount:0 mapping:0000000000000000 index:0x0
flags: 0xfffe0000000200(slab)
raw: 00fffe0000000200 ffffea000299f588 ffffea000263d0c8 ffff8880aa000e00
raw: 0000000000000000 ffff888088ec3000 0000000100000001 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
 ffff888088ec3280: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff888088ec3300: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>ffff888088ec3380: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
                                     ^
 ffff888088ec3400: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff888088ec3480: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
==================================================================


---
This bug is generated by a bot. It may contain errors.
See https://goo.gl/tpsmEJ for more information about syzbot.
syzbot engineers can be reached at syzkaller@googlegroups.com.

syzbot will keep track of this bug report. See:
https://goo.gl/tpsmEJ#status for how to communicate with syzbot.

^ permalink raw reply	[flat|nested] 8+ messages in thread

* Re: KASAN: use-after-free Read in addr_handler (2)
       [not found] ` <20200614085321.8740-1-hdanton@sina.com>
@ 2020-06-27  0:45   ` Jason Gunthorpe
  2020-06-27  2:38     ` [PATCH] RDMA/cma: Execute rdma_cm destruction from a handler properly kernel test robot
       [not found]   ` <20200627130205.16900-1-hdanton@sina.com>
  1 sibling, 1 reply; 8+ messages in thread
From: Jason Gunthorpe @ 2020-06-27  0:45 UTC (permalink / raw)
  To: Hillf Danton
  Cc: syzbot, chuck.lever, dledford, leon, linux-kernel, linux-rdma,
	parav, Markus Elfring, syzkaller-bugs

On Sun, Jun 14, 2020 at 04:53:21PM +0800, Hillf Danton wrote:
> 
> Wed, 10 Jun 2020 10:02:11 -0700
> > syzbot found the following crash on:
> > 
> > HEAD commit:    7ae77150 Merge tag 'powerpc-5.8-1' of git://git.kernel.org..
> > git tree:       upstream
> > console output: https://syzkaller.appspot.com/x/log.txt?x=16c0d3a6100000
> > kernel config:  https://syzkaller.appspot.com/x/.config?x=d195fe572fb15312
> > dashboard link: https://syzkaller.appspot.com/bug?extid=a929647172775e335941
> > compiler:       gcc (GCC) 9.0.0 20181231 (experimental)
> > 
> > Unfortunately, I don't have any reproducer for this crash yet.
> > 
> > IMPORTANT: if you fix the bug, please add the following tag to the commit:
> > Reported-by: syzbot+a929647172775e335941@syzkaller.appspotmail.com
> > 
> > ==================================================================
> > BUG: KASAN: use-after-free in __mutex_lock_common kernel/locking/mutex.c:938 [inline]
> > BUG: KASAN: use-after-free in __mutex_lock+0x1033/0x13c0 kernel/locking/mutex.c:1103
> > Read of size 8 at addr ffff888088ec33b0 by task kworker/u4:5/14014
> > 
> > CPU: 1 PID: 14014 Comm: kworker/u4:5 Not tainted 5.7.0-syzkaller #0
> > Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
> > Workqueue: ib_addr process_one_req
> > Call Trace:
> >  __dump_stack lib/dump_stack.c:77 [inline]
> >  dump_stack+0x188/0x20d lib/dump_stack.c:118
> >  print_address_description.constprop.0.cold+0xd3/0x413 mm/kasan/report.c:383
> >  __kasan_report mm/kasan/report.c:513 [inline]
> >  kasan_report.cold+0x1f/0x37 mm/kasan/report.c:530
> >  __mutex_lock_common kernel/locking/mutex.c:938 [inline]
> >  __mutex_lock+0x1033/0x13c0 kernel/locking/mutex.c:1103
> >  addr_handler+0xa0/0x340 drivers/infiniband/core/cma.c:3100
> >  process_one_req+0xfa/0x680 drivers/infiniband/core/addr.c:643
> >  process_one_work+0x965/0x16a0 kernel/workqueue.c:2268
> >  worker_thread+0x96/0xe20 kernel/workqueue.c:2414
> >  kthread+0x388/0x470 kernel/kthread.c:268
> >  ret_from_fork+0x24/0x30 arch/x86/entry/entry_64.S:351
> > 
> > Allocated by task 31499:
> >  save_stack+0x1b/0x40 mm/kasan/common.c:48
> >  set_track mm/kasan/common.c:56 [inline]
> >  __kasan_kmalloc mm/kasan/common.c:494 [inline]
> >  __kasan_kmalloc.constprop.0+0xbf/0xd0 mm/kasan/common.c:467
> >  kmem_cache_alloc_trace+0x153/0x7d0 mm/slab.c:3551
> >  kmalloc include/linux/slab.h:555 [inline]
> >  kzalloc include/linux/slab.h:669 [inline]
> >  __rdma_create_id+0x5b/0x850 drivers/infiniband/core/cma.c:861
> >  ucma_create_id+0x1d1/0x590 drivers/infiniband/core/ucma.c:503
> >  ucma_write+0x285/0x350 drivers/infiniband/core/ucma.c:1729
> >  __vfs_write+0x76/0x100 fs/read_write.c:495
> >  vfs_write+0x268/0x5d0 fs/read_write.c:559
> >  ksys_write+0x1ee/0x250 fs/read_write.c:612
> >  do_syscall_64+0xf6/0x7d0 arch/x86/entry/common.c:295
> >  entry_SYSCALL_64_after_hwframe+0x49/0xb3
> > 
> > Freed by task 31496:
> >  save_stack+0x1b/0x40 mm/kasan/common.c:48
> >  set_track mm/kasan/common.c:56 [inline]
> >  kasan_set_free_info mm/kasan/common.c:316 [inline]
> >  __kasan_slab_free+0xf7/0x140 mm/kasan/common.c:455
> >  __cache_free mm/slab.c:3426 [inline]
> >  kfree+0x109/0x2b0 mm/slab.c:3757
> >  ucma_close+0x111/0x300 drivers/infiniband/core/ucma.c:1807
> >  __fput+0x33e/0x880 fs/file_table.c:281
> >  task_work_run+0xf4/0x1b0 kernel/task_work.c:123
> >  tracehook_notify_resume include/linux/tracehook.h:188 [inline]
> >  exit_to_usermode_loop+0x2fa/0x360 arch/x86/entry/common.c:165
> >  prepare_exit_to_usermode arch/x86/entry/common.c:196 [inline]
> >  syscall_return_slowpath arch/x86/entry/common.c:279 [inline]
> >  do_syscall_64+0x6b1/0x7d0 arch/x86/entry/common.c:305
> >  entry_SYSCALL_64_after_hwframe+0x49/0xb3
> > 
> > The buggy address belongs to the object at ffff888088ec3000
> >  which belongs to the cache kmalloc-2k of size 2048
> > The buggy address is located 944 bytes inside of
> >  2048-byte region [ffff888088ec3000, ffff888088ec3800)
> > The buggy address belongs to the page:
> > page:ffffea000223b0c0 refcount:1 mapcount:0 mapping:0000000000000000 index:0x0
> > flags: 0xfffe0000000200(slab)
> > raw: 00fffe0000000200 ffffea000299f588 ffffea000263d0c8 ffff8880aa000e00
> > raw: 0000000000000000 ffff888088ec3000 0000000100000001 0000000000000000
> > page dumped because: kasan: bad access detected
> > 
> > Memory state around the buggy address:
> >  ffff888088ec3280: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
> >  ffff888088ec3300: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
> > >ffff888088ec3380: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
> >                                      ^
> >  ffff888088ec3400: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
> >  ffff888088ec3480: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
> > ==================================================================
> 
> Add extra grab to id_priv to make addr_handler() safe.
> It may also fix what's
>   Reported-by: syzbot+08092148130652a6faae@syzkaller.appspotmail.com

In some way adding the refcounting is appealing, but it is not quite
right..

Once rdma_resolve_addr() is called the cm_id state is supposed to go
to RDMA_CM_ADDR_QUERY and stay there until the address is resolved.

The first thing rdma_destroy_id() does (which is what triggered the
kfree) is to call cma_cancel_operation(), which does a
cancel_delayed_work_sync().

So, to hit this syzkaller one of these must have happened:
 1) rdma_addr_cancel() didn't work and the process_one_work() is still
    runnable/running
 2) The state changed away from RDMA_CM_ADDR_QUERY without doing
    rdma_addr_cancel()
 3) rdma_resolve_addr() ran concurrently with rdma_destroy_id()

I think #1 and #3 are not likely as I've already fixed those in the
past, but maybe you can see something?

So, this is probably #2. Actually it looks like there are many cases
where #2 is possible, so lets start there.

Something sort of like this should help:

From 036b462378a376725d81072c47754a89a51e4774 Mon Sep 17 00:00:00 2001
From: Jason Gunthorpe <jgg@nvidia.com>
Date: Fri, 26 Jun 2020 16:54:30 -0300
Subject: [PATCH] RDMA/cma: Execute rdma_cm destruction from a handler properly

When a rdma_cm_id needs to be destroyed after a handler callback fails,
part of the destruction pattern is open coded into each call site.

Unfortunately the blind assignment to state discards important information
needed to do cma_cancel_operation(). This results in active operations
being left running after rdma_destroy_id() completes, and the
use-after-free bugs from KASAN.

Consolidate this entire pattern into destroy_id_handler_unlock() and
manage the locking correctly. The state should be set to
RDMA_CM_DESTROYING under the handler_lock to atomically ensure no futher
handlers are called.

Reported-by: syzbot+a929647172775e335941@syzkaller.appspotmail.com
Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>
---
 drivers/infiniband/core/cma.c | 212 ++++++++++++++++------------------
 1 file changed, 101 insertions(+), 111 deletions(-)

diff --git a/drivers/infiniband/core/cma.c b/drivers/infiniband/core/cma.c
index 3d7cc9f0f3d40c..a599a628e45dc7 100644
--- a/drivers/infiniband/core/cma.c
+++ b/drivers/infiniband/core/cma.c
@@ -1825,23 +1825,11 @@ static void cma_leave_mc_groups(struct rdma_id_private *id_priv)
 	}
 }
 
-void rdma_destroy_id(struct rdma_cm_id *id)
+static void _destroy_id(struct rdma_id_private *id_priv,
+			enum rdma_cm_state state)
 {
-	struct rdma_id_private *id_priv;
-	enum rdma_cm_state state;
-
-	id_priv = container_of(id, struct rdma_id_private, id);
-	trace_cm_id_destroy(id_priv);
-	state = cma_exch(id_priv, RDMA_CM_DESTROYING);
 	cma_cancel_operation(id_priv, state);
 
-	/*
-	 * Wait for any active callback to finish.  New callbacks will find
-	 * the id_priv state set to destroying and abort.
-	 */
-	mutex_lock(&id_priv->handler_mutex);
-	mutex_unlock(&id_priv->handler_mutex);
-
 	rdma_restrack_del(&id_priv->res);
 	if (id_priv->cma_dev) {
 		if (rdma_cap_ib_cm(id_priv->id.device, 1)) {
@@ -1870,6 +1858,38 @@ void rdma_destroy_id(struct rdma_cm_id *id)
 	put_net(id_priv->id.route.addr.dev_addr.net);
 	kfree(id_priv);
 }
+
+/*
+ * destroy an ID from within the handler_mutex. This ensures that no other
+ * handlers can start running concurrently.
+ */
+static void destroy_id_handler_unlock(struct rdma_id_private *id_priv)
+	__releases(&idprv->handler_mutex)
+{
+	enum rdma_cm_state state;
+
+	trace_cm_id_destroy(id_priv);
+
+	/*
+	 * Setting the state to destroyed under the handler mutex provides a
+	 * fence against calling handler callbacks. If this is invoked due to
+	 * the failure of a handler callback then it guarentees that no future
+	 * handlers will be called.
+	 */
+	lockdep_assert_held(&id_priv->handler_mutex);
+	state = cma_exch(id_priv, RDMA_CM_DESTROYING);
+	mutex_unlock(&id_priv->handler_mutex);
+	_destroy_id(id_priv, state);
+}
+
+void rdma_destroy_id(struct rdma_cm_id *id)
+{
+	struct rdma_id_private *id_priv =
+		container_of(id, struct rdma_id_private, id);
+
+	mutex_lock(&id_priv->handler_mutex);
+	destroy_id_handler_unlock(id_priv);
+}
 EXPORT_SYMBOL(rdma_destroy_id);
 
 static int cma_rep_recv(struct rdma_id_private *id_priv)
@@ -2001,9 +2021,7 @@ static int cma_ib_handler(struct ib_cm_id *cm_id,
 	if (ret) {
 		/* Destroy the CM ID by returning a non-zero value. */
 		id_priv->cm_id.ib = NULL;
-		cma_exch(id_priv, RDMA_CM_DESTROYING);
-		mutex_unlock(&id_priv->handler_mutex);
-		rdma_destroy_id(&id_priv->id);
+		destroy_id_handler_unlock(id_priv);
 		return ret;
 	}
 out:
@@ -2170,7 +2188,7 @@ static int cma_ib_req_handler(struct ib_cm_id *cm_id,
 	mutex_lock(&listen_id->handler_mutex);
 	if (listen_id->state != RDMA_CM_LISTEN) {
 		ret = -ECONNABORTED;
-		goto err1;
+		goto err_unlock;
 	}
 
 	offset = cma_user_data_offset(listen_id);
@@ -2187,55 +2205,38 @@ static int cma_ib_req_handler(struct ib_cm_id *cm_id,
 	}
 	if (!conn_id) {
 		ret = -ENOMEM;
-		goto err1;
+		goto err_unlock;
 	}
 
 	mutex_lock_nested(&conn_id->handler_mutex, SINGLE_DEPTH_NESTING);
 	ret = cma_ib_acquire_dev(conn_id, listen_id, &req);
-	if (ret)
-		goto err2;
+	if (ret) {
+		destroy_id_handler_unlock(conn_id);
+		goto err_unlock;
+	}
 
 	conn_id->cm_id.ib = cm_id;
 	cm_id->context = conn_id;
 	cm_id->cm_handler = cma_ib_handler;
 
-	/*
-	 * Protect against the user destroying conn_id from another thread
-	 * until we're done accessing it.
-	 */
-	cma_id_get(conn_id);
 	ret = cma_cm_event_handler(conn_id, &event);
-	if (ret)
-		goto err3;
-	/*
-	 * Acquire mutex to prevent user executing rdma_destroy_id()
-	 * while we're accessing the cm_id.
-	 */
-	mutex_lock(&lock);
+	if (ret) {
+		/* Destroy the CM ID by returning a non-zero value. */
+		conn_id->cm_id.ib = NULL;
+		destroy_id_handler_unlock(conn_id);
+		goto err_unlock;
+	}
+
+	/* NOTE: Holding handler_mutex prevents concurrent destroy */
 	if (cma_comp(conn_id, RDMA_CM_CONNECT) &&
 	    (conn_id->id.qp_type != IB_QPT_UD)) {
 		trace_cm_send_mra(cm_id->context);
 		ib_send_cm_mra(cm_id, CMA_CM_MRA_SETTING, NULL, 0);
 	}
-	mutex_unlock(&lock);
 	mutex_unlock(&conn_id->handler_mutex);
-	mutex_unlock(&listen_id->handler_mutex);
-	cma_id_put(conn_id);
-	if (net_dev)
-		dev_put(net_dev);
-	return 0;
 
-err3:
-	cma_id_put(conn_id);
-	/* Destroy the CM ID by returning a non-zero value. */
-	conn_id->cm_id.ib = NULL;
-err2:
-	cma_exch(conn_id, RDMA_CM_DESTROYING);
-	mutex_unlock(&conn_id->handler_mutex);
-err1:
+err_unlock:
 	mutex_unlock(&listen_id->handler_mutex);
-	if (conn_id)
-		rdma_destroy_id(&conn_id->id);
 
 net_dev_put:
 	if (net_dev)
@@ -2335,9 +2336,7 @@ static int cma_iw_handler(struct iw_cm_id *iw_id, struct iw_cm_event *iw_event)
 	if (ret) {
 		/* Destroy the CM ID by returning a non-zero value. */
 		id_priv->cm_id.iw = NULL;
-		cma_exch(id_priv, RDMA_CM_DESTROYING);
-		mutex_unlock(&id_priv->handler_mutex);
-		rdma_destroy_id(&id_priv->id);
+		destroy_id_handler_unlock(id_priv);
 		return ret;
 	}
 
@@ -2384,15 +2383,13 @@ static int iw_conn_req_handler(struct iw_cm_id *cm_id,
 
 	ret = rdma_translate_ip(laddr, &conn_id->id.route.addr.dev_addr);
 	if (ret) {
-		mutex_unlock(&conn_id->handler_mutex);
-		rdma_destroy_id(new_cm_id);
+		destroy_id_handler_unlock(conn_id);
 		goto out;
 	}
 
 	ret = cma_iw_acquire_dev(conn_id, listen_id);
 	if (ret) {
-		mutex_unlock(&conn_id->handler_mutex);
-		rdma_destroy_id(new_cm_id);
+		destroy_id_handler_unlock(conn_id);
 		goto out;
 	}
 
@@ -2403,25 +2400,15 @@ static int iw_conn_req_handler(struct iw_cm_id *cm_id,
 	memcpy(cma_src_addr(conn_id), laddr, rdma_addr_size(laddr));
 	memcpy(cma_dst_addr(conn_id), raddr, rdma_addr_size(raddr));
 
-	/*
-	 * Protect against the user destroying conn_id from another thread
-	 * until we're done accessing it.
-	 */
-	cma_id_get(conn_id);
 	ret = cma_cm_event_handler(conn_id, &event);
 	if (ret) {
 		/* User wants to destroy the CM ID */
 		conn_id->cm_id.iw = NULL;
-		cma_exch(conn_id, RDMA_CM_DESTROYING);
-		mutex_unlock(&conn_id->handler_mutex);
-		mutex_unlock(&listen_id->handler_mutex);
-		cma_id_put(conn_id);
-		rdma_destroy_id(&conn_id->id);
-		return ret;
+		destroy_id_handler_unlock(conn_id);
+		goto out;
 	}
 
 	mutex_unlock(&conn_id->handler_mutex);
-	cma_id_put(conn_id);
 
 out:
 	mutex_unlock(&listen_id->handler_mutex);
@@ -2478,6 +2465,10 @@ static int cma_listen_handler(struct rdma_cm_id *id,
 {
 	struct rdma_id_private *id_priv = id->context;
 
+	/* Listening IDs are always destroyed on removal */
+	if (event->event == RDMA_CM_EVENT_DEVICE_REMOVAL)
+		return -1;
+
 	id->context = id_priv->id.context;
 	id->event_handler = id_priv->id.event_handler;
 	trace_cm_event_handler(id_priv, event);
@@ -2651,21 +2642,21 @@ static void cma_work_handler(struct work_struct *_work)
 {
 	struct cma_work *work = container_of(_work, struct cma_work, work);
 	struct rdma_id_private *id_priv = work->id;
-	int destroy = 0;
 
 	mutex_lock(&id_priv->handler_mutex);
 	if (!cma_comp_exch(id_priv, work->old_state, work->new_state))
-		goto out;
+		goto out_unlock;
 
 	if (cma_cm_event_handler(id_priv, &work->event)) {
-		cma_exch(id_priv, RDMA_CM_DESTROYING);
-		destroy = 1;
+		cma_id_put(id_priv);
+		destroy_id_handler_unlock(id_priv);
+		goto out_free;
 	}
-out:
+
+out_unlock:
 	mutex_unlock(&id_priv->handler_mutex);
 	cma_id_put(id_priv);
-	if (destroy)
-		rdma_destroy_id(&id_priv->id);
+out_free:
 	kfree(work);
 }
 
@@ -2673,23 +2664,22 @@ static void cma_ndev_work_handler(struct work_struct *_work)
 {
 	struct cma_ndev_work *work = container_of(_work, struct cma_ndev_work, work);
 	struct rdma_id_private *id_priv = work->id;
-	int destroy = 0;
 
 	mutex_lock(&id_priv->handler_mutex);
 	if (id_priv->state == RDMA_CM_DESTROYING ||
 	    id_priv->state == RDMA_CM_DEVICE_REMOVAL)
-		goto out;
+		goto out_unlock;
 
 	if (cma_cm_event_handler(id_priv, &work->event)) {
-		cma_exch(id_priv, RDMA_CM_DESTROYING);
-		destroy = 1;
+		cma_id_put(id_priv);
+		destroy_id_handler_unlock(id_priv);
+		goto out_free;
 	}
 
-out:
+out_unlock:
 	mutex_unlock(&id_priv->handler_mutex);
 	cma_id_put(id_priv);
-	if (destroy)
-		rdma_destroy_id(&id_priv->id);
+out_free:
 	kfree(work);
 }
 
@@ -3165,9 +3155,7 @@ static void addr_handler(int status, struct sockaddr *src_addr,
 		event.event = RDMA_CM_EVENT_ADDR_RESOLVED;
 
 	if (cma_cm_event_handler(id_priv, &event)) {
-		cma_exch(id_priv, RDMA_CM_DESTROYING);
-		mutex_unlock(&id_priv->handler_mutex);
-		rdma_destroy_id(&id_priv->id);
+		destroy_id_handler_unlock(id_priv);
 		return;
 	}
 out:
@@ -3822,9 +3810,7 @@ static int cma_sidr_rep_handler(struct ib_cm_id *cm_id,
 	if (ret) {
 		/* Destroy the CM ID by returning a non-zero value. */
 		id_priv->cm_id.ib = NULL;
-		cma_exch(id_priv, RDMA_CM_DESTROYING);
-		mutex_unlock(&id_priv->handler_mutex);
-		rdma_destroy_id(&id_priv->id);
+		destroy_id_handler_unlock(id_priv);
 		return ret;
 	}
 out:
@@ -4354,9 +4340,7 @@ static int cma_ib_mc_handler(int status, struct ib_sa_multicast *multicast)
 
 	rdma_destroy_ah_attr(&event.param.ud.ah_attr);
 	if (ret) {
-		cma_exch(id_priv, RDMA_CM_DESTROYING);
-		mutex_unlock(&id_priv->handler_mutex);
-		rdma_destroy_id(&id_priv->id);
+		destroy_id_handler_unlock(id_priv);
 		return 0;
 	}
 
@@ -4771,29 +4755,38 @@ static int cma_add_one(struct ib_device *device)
 	return ret;
 }
 
-static int cma_remove_id_dev(struct rdma_id_private *id_priv)
+static void cma_send_device_removal_put(struct rdma_id_private *id_priv)
 {
-	struct rdma_cm_event event = {};
+	struct rdma_cm_event event = { .event = RDMA_CM_EVENT_DEVICE_REMOVAL };
 	enum rdma_cm_state state;
-	int ret = 0;
+	unsigned long flags;
 
 	/* Record that we want to remove the device */
-	state = cma_exch(id_priv, RDMA_CM_DEVICE_REMOVAL);
-	if (state == RDMA_CM_DESTROYING)
-		return 0;
-
-	cma_cancel_operation(id_priv, state);
 	mutex_lock(&id_priv->handler_mutex);
+	spin_lock_irqsave(&id_priv->lock, flags);
+	state = id_priv->state;
+	if (state == RDMA_CM_DESTROYING || state == RDMA_CM_DEVICE_REMOVAL) {
+		spin_unlock_irqsave(&id_priv->lock, flags);
+		mutex_unlock(&id_priv->handler_mutex);
+		cm_id_put(id_priv);
+		return;
+	}
+	id_priv->state = RDMA_CM_DEVICE_REMOVAL;
+	spin_unlock_irqsave(&id_priv->lock, flags);
 
-	/* Check for destruction from another callback. */
-	if (!cma_comp(id_priv, RDMA_CM_DEVICE_REMOVAL))
-		goto out;
-
-	event.event = RDMA_CM_EVENT_DEVICE_REMOVAL;
-	ret = cma_cm_event_handler(id_priv, &event);
-out:
+	if (cma_cm_event_handler(id_priv, &event)) {
+		mutex_unlock(&id_priv->handler_mutex);
+		cm_id_put(id_priv);
+		trace_cm_id_destroy(id_priv);
+		_destroy_id(id_priv, state);
+		return;
+	}
 	mutex_unlock(&id_priv->handler_mutex);
-	return ret;
+
+	/* The thread that assigns state does the cancel */
+	cma_cancel_operation(id_priv, state);
+
+	cm_id_put(id_priv);
 }
 
 static void cma_process_remove(struct cma_device *cma_dev)
@@ -4811,10 +4804,7 @@ static void cma_process_remove(struct cma_device *cma_dev)
 		cma_id_get(id_priv);
 		mutex_unlock(&lock);
 
-		ret = id_priv->internal_id ? 1 : cma_remove_id_dev(id_priv);
-		cma_id_put(id_priv);
-		if (ret)
-			rdma_destroy_id(&id_priv->id);
+		cma_send_device_removal_put(id_priv);
 
 		mutex_lock(&lock);
 	}
-- 
2.27.0


^ permalink raw reply	[flat|nested] 8+ messages in thread

* Re: [PATCH] RDMA/cma: Execute rdma_cm destruction from a handler properly
  2020-06-27  0:45   ` Jason Gunthorpe
@ 2020-06-27  2:38     ` kernel test robot
  0 siblings, 0 replies; 8+ messages in thread
From: kernel test robot @ 2020-06-27  2:38 UTC (permalink / raw)
  To: Jason Gunthorpe, Hillf Danton
  Cc: kbuild-all, syzbot, chuck.lever, dledford, leon, linux-kernel,
	linux-rdma, parav, Markus Elfring, syzkaller-bugs

[-- Attachment #1: Type: text/plain, Size: 3372 bytes --]

Hi Jason,

I love your patch! Yet something to improve:

[auto build test ERROR on linus/master]
[also build test ERROR on v5.8-rc2 next-20200626]
[If your patch is applied to the wrong git tree, kindly drop us a note.
And when submitting patch, we suggest to use  as documented in
https://git-scm.com/docs/git-format-patch]

url:    https://github.com/0day-ci/linux/commits/Jason-Gunthorpe/RDMA-cma-Execute-rdma_cm-destruction-from-a-handler-properly/20200627-084914
base:   https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git 1590a2e1c681b0991bd42c992cabfd380e0338f2
config: mips-allyesconfig (attached as .config)
compiler: mips-linux-gcc (GCC) 9.3.0
reproduce (this is a W=1 build):
        wget https://raw.githubusercontent.com/intel/lkp-tests/master/sbin/make.cross -O ~/bin/make.cross
        chmod +x ~/bin/make.cross
        # save the attached .config to linux build tree
        COMPILER_INSTALL_PATH=$HOME/0day COMPILER=gcc-9.3.0 make.cross ARCH=mips 

If you fix the issue, kindly add following tag as appropriate
Reported-by: kernel test robot <lkp@intel.com>

All errors (new ones prefixed by >>):

   drivers/infiniband/core/cma.c: In function 'cma_send_device_removal_put':
>> drivers/infiniband/core/cma.c:4787:3: error: implicit declaration of function 'spin_unlock_irqsave'; did you mean 'spin_lock_irqsave'? [-Werror=implicit-function-declaration]
    4787 |   spin_unlock_irqsave(&id_priv->lock, flags);
         |   ^~~~~~~~~~~~~~~~~~~
         |   spin_lock_irqsave
>> drivers/infiniband/core/cma.c:4789:3: error: implicit declaration of function 'cm_id_put'; did you mean 'cma_id_put'? [-Werror=implicit-function-declaration]
    4789 |   cm_id_put(id_priv);
         |   ^~~~~~~~~
         |   cma_id_put
   drivers/infiniband/core/cma.c: In function 'cma_process_remove':
   drivers/infiniband/core/cma.c:4813:6: warning: unused variable 'ret' [-Wunused-variable]
    4813 |  int ret;
         |      ^~~
   cc1: some warnings being treated as errors

vim +4787 drivers/infiniband/core/cma.c

  4775	
  4776	static void cma_send_device_removal_put(struct rdma_id_private *id_priv)
  4777	{
  4778		struct rdma_cm_event event = { .event = RDMA_CM_EVENT_DEVICE_REMOVAL };
  4779		enum rdma_cm_state state;
  4780		unsigned long flags;
  4781	
  4782		/* Record that we want to remove the device */
  4783		mutex_lock(&id_priv->handler_mutex);
  4784		spin_lock_irqsave(&id_priv->lock, flags);
  4785		state = id_priv->state;
  4786		if (state == RDMA_CM_DESTROYING || state == RDMA_CM_DEVICE_REMOVAL) {
> 4787			spin_unlock_irqsave(&id_priv->lock, flags);
  4788			mutex_unlock(&id_priv->handler_mutex);
> 4789			cm_id_put(id_priv);
  4790			return;
  4791		}
  4792		id_priv->state = RDMA_CM_DEVICE_REMOVAL;
  4793		spin_unlock_irqsave(&id_priv->lock, flags);
  4794	
  4795		if (cma_cm_event_handler(id_priv, &event)) {
  4796			mutex_unlock(&id_priv->handler_mutex);
  4797			cm_id_put(id_priv);
  4798			trace_cm_id_destroy(id_priv);
  4799			_destroy_id(id_priv, state);
  4800			return;
  4801		}
  4802		mutex_unlock(&id_priv->handler_mutex);
  4803	
  4804		/* The thread that assigns state does the cancel */
  4805		cma_cancel_operation(id_priv, state);
  4806	
  4807		cm_id_put(id_priv);
  4808	}
  4809	

---
0-DAY CI Kernel Test Service, Intel Corporation
https://lists.01.org/hyperkitty/list/kbuild-all@lists.01.org

[-- Attachment #2: .config.gz --]
[-- Type: application/gzip, Size: 67044 bytes --]

^ permalink raw reply	[flat|nested] 8+ messages in thread

* Re: KASAN: use-after-free Read in addr_handler (2)
       [not found]   ` <20200627130205.16900-1-hdanton@sina.com>
@ 2020-06-27 22:25     ` Jason Gunthorpe
  2020-06-29 14:42       ` Dmitry Vyukov
  0 siblings, 1 reply; 8+ messages in thread
From: Jason Gunthorpe @ 2020-06-27 22:25 UTC (permalink / raw)
  To: Hillf Danton
  Cc: syzbot, chuck.lever, dledford, leon, linux-kernel, linux-rdma,
	parav, Markus Elfring, syzkaller-bugs

On Sat, Jun 27, 2020 at 09:02:05PM +0800, Hillf Danton wrote:
> > So, to hit this syzkaller one of these must have happened:
> >  1) rdma_addr_cancel() didn't work and the process_one_work() is still
> >     runnable/running
> 
> What syzbot reported indicates that the kworker did survive not only
> canceling work but the handler_mutex, despite it's a sync cancel that
> waits for the work to complete.

The syzbot report doesn't confirm that the cancel work was actaully
called.

The most likely situation is that it was skipped because of the state
mangling the patch fixes..

> >  2) The state changed away from RDMA_CM_ADDR_QUERY without doing
> >     rdma_addr_cancel()
> 
> The cancel does cover the query state in the reported case, and have
> difficult time working out what's in the patch below preventing the
> work from going across the line the sync cancel draws. That's the
> question we can revisit once there is a reproducer available.

rdma-cm never seems to get reproducers from syzkaller

Jason

^ permalink raw reply	[flat|nested] 8+ messages in thread

* Re: KASAN: use-after-free Read in addr_handler (2)
  2020-06-27 22:25     ` KASAN: use-after-free Read in addr_handler (2) Jason Gunthorpe
@ 2020-06-29 14:42       ` Dmitry Vyukov
  2020-06-29 17:27         ` Dmitry Vyukov
  0 siblings, 1 reply; 8+ messages in thread
From: Dmitry Vyukov @ 2020-06-29 14:42 UTC (permalink / raw)
  To: Jason Gunthorpe, syzkaller
  Cc: Hillf Danton, syzbot, chuck.lever, Doug Ledford, Leon Romanovsky,
	LKML, RDMA mailing list, parav, Markus Elfring, syzkaller-bugs

On Sun, Jun 28, 2020 at 12:25 AM Jason Gunthorpe <jgg@ziepe.ca> wrote:
>
> On Sat, Jun 27, 2020 at 09:02:05PM +0800, Hillf Danton wrote:
> > > So, to hit this syzkaller one of these must have happened:
> > >  1) rdma_addr_cancel() didn't work and the process_one_work() is still
> > >     runnable/running
> >
> > What syzbot reported indicates that the kworker did survive not only
> > canceling work but the handler_mutex, despite it's a sync cancel that
> > waits for the work to complete.
>
> The syzbot report doesn't confirm that the cancel work was actaully
> called.
>
> The most likely situation is that it was skipped because of the state
> mangling the patch fixes..
>
> > >  2) The state changed away from RDMA_CM_ADDR_QUERY without doing
> > >     rdma_addr_cancel()
> >
> > The cancel does cover the query state in the reported case, and have
> > difficult time working out what's in the patch below preventing the
> > work from going across the line the sync cancel draws. That's the
> > question we can revisit once there is a reproducer available.
>
> rdma-cm never seems to get reproducers from syzkaller

+syzkaller mailing list

Hi Jason,

Wonder if there is some systematic issue. Let me double check.

^ permalink raw reply	[flat|nested] 8+ messages in thread

* Re: KASAN: use-after-free Read in addr_handler (2)
  2020-06-29 14:42       ` Dmitry Vyukov
@ 2020-06-29 17:27         ` Dmitry Vyukov
  2020-06-29 19:22           ` Jason Gunthorpe
  0 siblings, 1 reply; 8+ messages in thread
From: Dmitry Vyukov @ 2020-06-29 17:27 UTC (permalink / raw)
  To: Jason Gunthorpe, syzkaller
  Cc: Hillf Danton, syzbot, chuck.lever, Doug Ledford, Leon Romanovsky,
	LKML, RDMA mailing list, parav, Markus Elfring, syzkaller-bugs

On Mon, Jun 29, 2020 at 4:42 PM Dmitry Vyukov <dvyukov@google.com> wrote:
>
> On Sun, Jun 28, 2020 at 12:25 AM Jason Gunthorpe <jgg@ziepe.ca> wrote:
> >
> > On Sat, Jun 27, 2020 at 09:02:05PM +0800, Hillf Danton wrote:
> > > > So, to hit this syzkaller one of these must have happened:
> > > >  1) rdma_addr_cancel() didn't work and the process_one_work() is still
> > > >     runnable/running
> > >
> > > What syzbot reported indicates that the kworker did survive not only
> > > canceling work but the handler_mutex, despite it's a sync cancel that
> > > waits for the work to complete.
> >
> > The syzbot report doesn't confirm that the cancel work was actaully
> > called.
> >
> > The most likely situation is that it was skipped because of the state
> > mangling the patch fixes..
> >
> > > >  2) The state changed away from RDMA_CM_ADDR_QUERY without doing
> > > >     rdma_addr_cancel()
> > >
> > > The cancel does cover the query state in the reported case, and have
> > > difficult time working out what's in the patch below preventing the
> > > work from going across the line the sync cancel draws. That's the
> > > question we can revisit once there is a reproducer available.
> >
> > rdma-cm never seems to get reproducers from syzkaller
>
> +syzkaller mailing list
>
> Hi Jason,
>
> Wonder if there is some systematic issue. Let me double check.

By scanning bugs at:
https://syzkaller.appspot.com/upstream
https://syzkaller.appspot.com/upstream/fixed

I found a significant number of bugs that I would qualify as "rdma-cm"
and that have reproducers. Here is an incomplete list (I did not get
to the end):

https://syzkaller.appspot.com/bug?id=b8febdb3c7c8c1f1b606fb903cee66b21b2fd02f
https://syzkaller.appspot.com/bug?id=d5222b3e1659e0aea19df562c79f216515740daa
https://syzkaller.appspot.com/bug?id=c600e111223ce0a20e5f2fb4e9a4ebdff54d7fa6
https://syzkaller.appspot.com/bug?id=a9796acbdecc1b2ba927578917755899c63c48af
https://syzkaller.appspot.com/bug?id=95f89b8fb9fdc42e28ad586e657fea074e4e719b
https://syzkaller.appspot.com/bug?id=8dc0bcd9dd6ec915ba10b3354740eb420884acaa
https://syzkaller.appspot.com/bug?id=805ad726feb6910e35088ae7bbe61f4125e573b7
https://syzkaller.appspot.com/bug?id=56b60fb3340c5995373fe5b8eae9e8722a012fc4
https://syzkaller.appspot.com/bug?id=38d36d1b26b4299bf964d50af4d79688d39ab960
https://syzkaller.appspot.com/bug?id=25e00dd59f31783f233185cb60064b0ab645310f
https://syzkaller.appspot.com/bug?id=2f38d7e5312fdd0acc979c5e26ef2ef8f3370996

Do you mean some specific subset of bugs by "rdma-cm"? If yes, what is
that subset?

^ permalink raw reply	[flat|nested] 8+ messages in thread

* Re: KASAN: use-after-free Read in addr_handler (2)
  2020-06-29 17:27         ` Dmitry Vyukov
@ 2020-06-29 19:22           ` Jason Gunthorpe
  2020-06-29 19:41             ` Dmitry Vyukov
  0 siblings, 1 reply; 8+ messages in thread
From: Jason Gunthorpe @ 2020-06-29 19:22 UTC (permalink / raw)
  To: Dmitry Vyukov
  Cc: syzkaller, Hillf Danton, syzbot, chuck.lever, Doug Ledford,
	Leon Romanovsky, LKML, RDMA mailing list, parav, Markus Elfring,
	syzkaller-bugs

On Mon, Jun 29, 2020 at 07:27:40PM +0200, Dmitry Vyukov wrote:
> On Mon, Jun 29, 2020 at 4:42 PM Dmitry Vyukov <dvyukov@google.com> wrote:
> >
> > On Sun, Jun 28, 2020 at 12:25 AM Jason Gunthorpe <jgg@ziepe.ca> wrote:
> > >
> > > On Sat, Jun 27, 2020 at 09:02:05PM +0800, Hillf Danton wrote:
> > > > > So, to hit this syzkaller one of these must have happened:
> > > > >  1) rdma_addr_cancel() didn't work and the process_one_work() is still
> > > > >     runnable/running
> > > >
> > > > What syzbot reported indicates that the kworker did survive not only
> > > > canceling work but the handler_mutex, despite it's a sync cancel that
> > > > waits for the work to complete.
> > >
> > > The syzbot report doesn't confirm that the cancel work was actaully
> > > called.
> > >
> > > The most likely situation is that it was skipped because of the state
> > > mangling the patch fixes..
> > >
> > > > >  2) The state changed away from RDMA_CM_ADDR_QUERY without doing
> > > > >     rdma_addr_cancel()
> > > >
> > > > The cancel does cover the query state in the reported case, and have
> > > > difficult time working out what's in the patch below preventing the
> > > > work from going across the line the sync cancel draws. That's the
> > > > question we can revisit once there is a reproducer available.
> > >
> > > rdma-cm never seems to get reproducers from syzkaller
> >
> > +syzkaller mailing list
> >
> > Hi Jason,
> >
> > Wonder if there is some systematic issue. Let me double check.
> 
> By scanning bugs at:
> https://syzkaller.appspot.com/upstream
> https://syzkaller.appspot.com/upstream/fixed
> 
> I found a significant number of bugs that I would qualify as "rdma-cm"
> and that have reproducers. Here is an incomplete list (I did not get
> to the end):
> 
> https://syzkaller.appspot.com/bug?id=b8febdb3c7c8c1f1b606fb903cee66b21b2fd02f
> https://syzkaller.appspot.com/bug?id=d5222b3e1659e0aea19df562c79f216515740daa
> https://syzkaller.appspot.com/bug?id=c600e111223ce0a20e5f2fb4e9a4ebdff54d7fa6
> https://syzkaller.appspot.com/bug?id=a9796acbdecc1b2ba927578917755899c63c48af
> https://syzkaller.appspot.com/bug?id=95f89b8fb9fdc42e28ad586e657fea074e4e719b
> https://syzkaller.appspot.com/bug?id=8dc0bcd9dd6ec915ba10b3354740eb420884acaa
> https://syzkaller.appspot.com/bug?id=805ad726feb6910e35088ae7bbe61f4125e573b7
> https://syzkaller.appspot.com/bug?id=56b60fb3340c5995373fe5b8eae9e8722a012fc4
> https://syzkaller.appspot.com/bug?id=38d36d1b26b4299bf964d50af4d79688d39ab960
> https://syzkaller.appspot.com/bug?id=25e00dd59f31783f233185cb60064b0ab645310f
> https://syzkaller.appspot.com/bug?id=2f38d7e5312fdd0acc979c5e26ef2ef8f3370996
> 
> Do you mean some specific subset of bugs by "rdma-cm"? If yes, what is
> that subset?

The race condition bugs never seem to get reproducers, I checked a few
of the above and these are much more deterministic things.

I think the recurrance rate for the races is probably too low?

Jason

^ permalink raw reply	[flat|nested] 8+ messages in thread

* Re: KASAN: use-after-free Read in addr_handler (2)
  2020-06-29 19:22           ` Jason Gunthorpe
@ 2020-06-29 19:41             ` Dmitry Vyukov
  0 siblings, 0 replies; 8+ messages in thread
From: Dmitry Vyukov @ 2020-06-29 19:41 UTC (permalink / raw)
  To: Jason Gunthorpe
  Cc: syzkaller, Hillf Danton, syzbot, chuck.lever, Doug Ledford,
	Leon Romanovsky, LKML, RDMA mailing list, parav, Markus Elfring,
	syzkaller-bugs

On Mon, Jun 29, 2020 at 9:22 PM Jason Gunthorpe <jgg@ziepe.ca> wrote:
> > > > On Sat, Jun 27, 2020 at 09:02:05PM +0800, Hillf Danton wrote:
> > > > > > So, to hit this syzkaller one of these must have happened:
> > > > > >  1) rdma_addr_cancel() didn't work and the process_one_work() is still
> > > > > >     runnable/running
> > > > >
> > > > > What syzbot reported indicates that the kworker did survive not only
> > > > > canceling work but the handler_mutex, despite it's a sync cancel that
> > > > > waits for the work to complete.
> > > >
> > > > The syzbot report doesn't confirm that the cancel work was actaully
> > > > called.
> > > >
> > > > The most likely situation is that it was skipped because of the state
> > > > mangling the patch fixes..
> > > >
> > > > > >  2) The state changed away from RDMA_CM_ADDR_QUERY without doing
> > > > > >     rdma_addr_cancel()
> > > > >
> > > > > The cancel does cover the query state in the reported case, and have
> > > > > difficult time working out what's in the patch below preventing the
> > > > > work from going across the line the sync cancel draws. That's the
> > > > > question we can revisit once there is a reproducer available.
> > > >
> > > > rdma-cm never seems to get reproducers from syzkaller
> > >
> > > +syzkaller mailing list
> > >
> > > Hi Jason,
> > >
> > > Wonder if there is some systematic issue. Let me double check.
> >
> > By scanning bugs at:
> > https://syzkaller.appspot.com/upstream
> > https://syzkaller.appspot.com/upstream/fixed
> >
> > I found a significant number of bugs that I would qualify as "rdma-cm"
> > and that have reproducers. Here is an incomplete list (I did not get
> > to the end):
> >
> > https://syzkaller.appspot.com/bug?id=b8febdb3c7c8c1f1b606fb903cee66b21b2fd02f
> > https://syzkaller.appspot.com/bug?id=d5222b3e1659e0aea19df562c79f216515740daa
> > https://syzkaller.appspot.com/bug?id=c600e111223ce0a20e5f2fb4e9a4ebdff54d7fa6
> > https://syzkaller.appspot.com/bug?id=a9796acbdecc1b2ba927578917755899c63c48af
> > https://syzkaller.appspot.com/bug?id=95f89b8fb9fdc42e28ad586e657fea074e4e719b
> > https://syzkaller.appspot.com/bug?id=8dc0bcd9dd6ec915ba10b3354740eb420884acaa
> > https://syzkaller.appspot.com/bug?id=805ad726feb6910e35088ae7bbe61f4125e573b7
> > https://syzkaller.appspot.com/bug?id=56b60fb3340c5995373fe5b8eae9e8722a012fc4
> > https://syzkaller.appspot.com/bug?id=38d36d1b26b4299bf964d50af4d79688d39ab960
> > https://syzkaller.appspot.com/bug?id=25e00dd59f31783f233185cb60064b0ab645310f
> > https://syzkaller.appspot.com/bug?id=2f38d7e5312fdd0acc979c5e26ef2ef8f3370996
> >
> > Do you mean some specific subset of bugs by "rdma-cm"? If yes, what is
> > that subset?
>
> The race condition bugs never seem to get reproducers, I checked a few
> of the above and these are much more deterministic things.
>
> I think the recurrance rate for the races is probably too low?

Yes, it definitely may depend on probability. There is usually a
significant correlation with the number of crashes. This bug happened
only once, that usually means either a very hard to trigger race
condition, or a previous induced memory corruption. For harder to
trigger race conditions, KCSAN (the data race detector) may help in
future. However, kernel has too many races to report them to mailing
lists:
https://syzkaller.appspot.com/upstream?manager=ci2-upstream-kcsan-gce
Though, some race conditions are manageable to trigger and I think we
have hundreds of race conditions with reproducers on the dashboard.

^ permalink raw reply	[flat|nested] 8+ messages in thread

end of thread, other threads:[~2020-06-29 19:42 UTC | newest]

Thread overview: 8+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2020-06-10 17:02 KASAN: use-after-free Read in addr_handler (2) syzbot
     [not found] ` <20200614085321.8740-1-hdanton@sina.com>
2020-06-27  0:45   ` Jason Gunthorpe
2020-06-27  2:38     ` [PATCH] RDMA/cma: Execute rdma_cm destruction from a handler properly kernel test robot
     [not found]   ` <20200627130205.16900-1-hdanton@sina.com>
2020-06-27 22:25     ` KASAN: use-after-free Read in addr_handler (2) Jason Gunthorpe
2020-06-29 14:42       ` Dmitry Vyukov
2020-06-29 17:27         ` Dmitry Vyukov
2020-06-29 19:22           ` Jason Gunthorpe
2020-06-29 19:41             ` Dmitry Vyukov

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