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af_unix: Suppress false-positive lockdep splat for spin_lock() in __unix_gc().
jira LE-2015 Rebuild_History Non-Buildable kernel-5.14.0-427.42.1.el9_4 commit-author Kuniyuki Iwashima <kuniyu@amazon.com> commit 1971d13 Empty-Commit: Cherry-Pick Conflicts during history rebuild. Will be included in final tarball splat. Ref for failed cherry-pick at: ciq/ciq_backports/kernel-5.14.0-427.42.1.el9_4/1971d13f.failed syzbot reported a lockdep splat regarding unix_gc_lock and unix_state_lock(). One is called from recvmsg() for a connected socket, and another is called from GC for TCP_LISTEN socket. So, the splat is false-positive. Let's add a dedicated lock class for the latter to suppress the splat. Note that this change is not necessary for net-next.git as the issue is only applied to the old GC impl. [0]: WARNING: possible circular locking dependency detected 6.9.0-rc5-syzkaller-00007-g4d2008430ce8 #0 Not tainted ----------------------------------------------------- kworker/u8:1/11 is trying to acquire lock: ffff88807cea4e70 (&u->lock){+.+.}-{2:2}, at: spin_lock include/linux/spinlock.h:351 [inline] ffff88807cea4e70 (&u->lock){+.+.}-{2:2}, at: __unix_gc+0x40e/0xf70 net/unix/garbage.c:302 but task is already holding lock: ffffffff8f6ab638 (unix_gc_lock){+.+.}-{2:2}, at: spin_lock include/linux/spinlock.h:351 [inline] ffffffff8f6ab638 (unix_gc_lock){+.+.}-{2:2}, at: __unix_gc+0x117/0xf70 net/unix/garbage.c:261 which lock already depends on the new lock. the existing dependency chain (in reverse order) is: -> #1 (unix_gc_lock){+.+.}-{2:2}: lock_acquire+0x1ed/0x550 kernel/locking/lockdep.c:5754 __raw_spin_lock include/linux/spinlock_api_smp.h:133 [inline] _raw_spin_lock+0x2e/0x40 kernel/locking/spinlock.c:154 spin_lock include/linux/spinlock.h:351 [inline] unix_notinflight+0x13d/0x390 net/unix/garbage.c:140 unix_detach_fds net/unix/af_unix.c:1819 [inline] unix_destruct_scm+0x221/0x350 net/unix/af_unix.c:1876 skb_release_head_state+0x100/0x250 net/core/skbuff.c:1188 skb_release_all net/core/skbuff.c:1200 [inline] __kfree_skb net/core/skbuff.c:1216 [inline] kfree_skb_reason+0x16d/0x3b0 net/core/skbuff.c:1252 kfree_skb include/linux/skbuff.h:1262 [inline] manage_oob net/unix/af_unix.c:2672 [inline] unix_stream_read_generic+0x1125/0x2700 net/unix/af_unix.c:2749 unix_stream_splice_read+0x239/0x320 net/unix/af_unix.c:2981 do_splice_read fs/splice.c:985 [inline] splice_file_to_pipe+0x299/0x500 fs/splice.c:1295 do_splice+0xf2d/0x1880 fs/splice.c:1379 __do_splice fs/splice.c:1436 [inline] __do_sys_splice fs/splice.c:1652 [inline] __se_sys_splice+0x331/0x4a0 fs/splice.c:1634 do_syscall_x64 arch/x86/entry/common.c:52 [inline] do_syscall_64+0xf5/0x240 arch/x86/entry/common.c:83 entry_SYSCALL_64_after_hwframe+0x77/0x7f -> #0 (&u->lock){+.+.}-{2:2}: check_prev_add kernel/locking/lockdep.c:3134 [inline] check_prevs_add kernel/locking/lockdep.c:3253 [inline] validate_chain+0x18cb/0x58e0 kernel/locking/lockdep.c:3869 __lock_acquire+0x1346/0x1fd0 kernel/locking/lockdep.c:5137 lock_acquire+0x1ed/0x550 kernel/locking/lockdep.c:5754 __raw_spin_lock include/linux/spinlock_api_smp.h:133 [inline] _raw_spin_lock+0x2e/0x40 kernel/locking/spinlock.c:154 spin_lock include/linux/spinlock.h:351 [inline] __unix_gc+0x40e/0xf70 net/unix/garbage.c:302 process_one_work kernel/workqueue.c:3254 [inline] process_scheduled_works+0xa10/0x17c0 kernel/workqueue.c:3335 worker_thread+0x86d/0xd70 kernel/workqueue.c:3416 kthread+0x2f0/0x390 kernel/kthread.c:388 ret_from_fork+0x4b/0x80 arch/x86/kernel/process.c:147 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:244 other info that might help us debug this: Possible unsafe locking scenario: CPU0 CPU1 ---- ---- lock(unix_gc_lock); lock(&u->lock); lock(unix_gc_lock); lock(&u->lock); *** DEADLOCK *** 3 locks held by kworker/u8:1/11: #0: ffff888015089148 ((wq_completion)events_unbound){+.+.}-{0:0}, at: process_one_work kernel/workqueue.c:3229 [inline] #0: ffff888015089148 ((wq_completion)events_unbound){+.+.}-{0:0}, at: process_scheduled_works+0x8e0/0x17c0 kernel/workqueue.c:3335 #1: ffffc90000107d00 (unix_gc_work){+.+.}-{0:0}, at: process_one_work kernel/workqueue.c:3230 [inline] #1: ffffc90000107d00 (unix_gc_work){+.+.}-{0:0}, at: process_scheduled_works+0x91b/0x17c0 kernel/workqueue.c:3335 #2: ffffffff8f6ab638 (unix_gc_lock){+.+.}-{2:2}, at: spin_lock include/linux/spinlock.h:351 [inline] #2: ffffffff8f6ab638 (unix_gc_lock){+.+.}-{2:2}, at: __unix_gc+0x117/0xf70 net/unix/garbage.c:261 stack backtrace: CPU: 0 PID: 11 Comm: kworker/u8:1 Not tainted 6.9.0-rc5-syzkaller-00007-g4d2008430ce8 #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 03/27/2024 Workqueue: events_unbound __unix_gc Call Trace: <TASK> __dump_stack lib/dump_stack.c:88 [inline] dump_stack_lvl+0x241/0x360 lib/dump_stack.c:114 check_noncircular+0x36a/0x4a0 kernel/locking/lockdep.c:2187 check_prev_add kernel/locking/lockdep.c:3134 [inline] check_prevs_add kernel/locking/lockdep.c:3253 [inline] validate_chain+0x18cb/0x58e0 kernel/locking/lockdep.c:3869 __lock_acquire+0x1346/0x1fd0 kernel/locking/lockdep.c:5137 lock_acquire+0x1ed/0x550 kernel/locking/lockdep.c:5754 __raw_spin_lock include/linux/spinlock_api_smp.h:133 [inline] _raw_spin_lock+0x2e/0x40 kernel/locking/spinlock.c:154 spin_lock include/linux/spinlock.h:351 [inline] __unix_gc+0x40e/0xf70 net/unix/garbage.c:302 process_one_work kernel/workqueue.c:3254 [inline] process_scheduled_works+0xa10/0x17c0 kernel/workqueue.c:3335 worker_thread+0x86d/0xd70 kernel/workqueue.c:3416 kthread+0x2f0/0x390 kernel/kthread.c:388 ret_from_fork+0x4b/0x80 arch/x86/kernel/process.c:147 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:244 </TASK> Fixes: 47d8ac0 ("af_unix: Fix garbage collector racing against connect()") Reported-and-tested-by: syzbot+fa379358c28cc87cc307@syzkaller.appspotmail.com Closes: https://syzkaller.appspot.com/bug?extid=fa379358c28cc87cc307 Signed-off-by: Kuniyuki Iwashima <kuniyu@amazon.com> Link: https://lore.kernel.org/r/20240424170443.9832-1-kuniyu@amazon.com Signed-off-by: Jakub Kicinski <kuba@kernel.org> (cherry picked from commit 1971d13) Signed-off-by: Jonathan Maple <jmaple@ciq.com> # Conflicts: # net/unix/garbage.c
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‎ciq/ciq_backports/kernel-5.14.0-427.42.1.el9_4/1971d13f.failed‎

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af_unix: Suppress false-positive lockdep splat for spin_lock() in __unix_gc().
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jira LE-2015
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Rebuild_History Non-Buildable kernel-5.14.0-427.42.1.el9_4
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commit-author Kuniyuki Iwashima <kuniyu@amazon.com>
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commit 1971d13ffa84a551d29a81fdf5b5ec5be166ac83
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Empty-Commit: Cherry-Pick Conflicts during history rebuild.
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Will be included in final tarball splat. Ref for failed cherry-pick at:
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ciq/ciq_backports/kernel-5.14.0-427.42.1.el9_4/1971d13f.failed
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syzbot reported a lockdep splat regarding unix_gc_lock and
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unix_state_lock().
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One is called from recvmsg() for a connected socket, and another
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is called from GC for TCP_LISTEN socket.
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So, the splat is false-positive.
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Let's add a dedicated lock class for the latter to suppress the splat.
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Note that this change is not necessary for net-next.git as the issue
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is only applied to the old GC impl.
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[0]:
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WARNING: possible circular locking dependency detected
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6.9.0-rc5-syzkaller-00007-g4d2008430ce8 #0 Not tainted
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-----------------------------------------------------
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kworker/u8:1/11 is trying to acquire lock:
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ffff88807cea4e70 (&u->lock){+.+.}-{2:2}, at: spin_lock include/linux/spinlock.h:351 [inline]
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ffff88807cea4e70 (&u->lock){+.+.}-{2:2}, at: __unix_gc+0x40e/0xf70 net/unix/garbage.c:302
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but task is already holding lock:
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ffffffff8f6ab638 (unix_gc_lock){+.+.}-{2:2}, at: spin_lock include/linux/spinlock.h:351 [inline]
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ffffffff8f6ab638 (unix_gc_lock){+.+.}-{2:2}, at: __unix_gc+0x117/0xf70 net/unix/garbage.c:261
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which lock already depends on the new lock.
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the existing dependency chain (in reverse order) is:
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-> #1 (unix_gc_lock){+.+.}-{2:2}:
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lock_acquire+0x1ed/0x550 kernel/locking/lockdep.c:5754
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__raw_spin_lock include/linux/spinlock_api_smp.h:133 [inline]
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_raw_spin_lock+0x2e/0x40 kernel/locking/spinlock.c:154
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spin_lock include/linux/spinlock.h:351 [inline]
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unix_notinflight+0x13d/0x390 net/unix/garbage.c:140
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unix_detach_fds net/unix/af_unix.c:1819 [inline]
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unix_destruct_scm+0x221/0x350 net/unix/af_unix.c:1876
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skb_release_head_state+0x100/0x250 net/core/skbuff.c:1188
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skb_release_all net/core/skbuff.c:1200 [inline]
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__kfree_skb net/core/skbuff.c:1216 [inline]
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kfree_skb_reason+0x16d/0x3b0 net/core/skbuff.c:1252
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kfree_skb include/linux/skbuff.h:1262 [inline]
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manage_oob net/unix/af_unix.c:2672 [inline]
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unix_stream_read_generic+0x1125/0x2700 net/unix/af_unix.c:2749
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unix_stream_splice_read+0x239/0x320 net/unix/af_unix.c:2981
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do_splice_read fs/splice.c:985 [inline]
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splice_file_to_pipe+0x299/0x500 fs/splice.c:1295
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do_splice+0xf2d/0x1880 fs/splice.c:1379
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__do_splice fs/splice.c:1436 [inline]
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__do_sys_splice fs/splice.c:1652 [inline]
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__se_sys_splice+0x331/0x4a0 fs/splice.c:1634
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do_syscall_x64 arch/x86/entry/common.c:52 [inline]
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do_syscall_64+0xf5/0x240 arch/x86/entry/common.c:83
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entry_SYSCALL_64_after_hwframe+0x77/0x7f
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-> #0 (&u->lock){+.+.}-{2:2}:
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check_prev_add kernel/locking/lockdep.c:3134 [inline]
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check_prevs_add kernel/locking/lockdep.c:3253 [inline]
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validate_chain+0x18cb/0x58e0 kernel/locking/lockdep.c:3869
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__lock_acquire+0x1346/0x1fd0 kernel/locking/lockdep.c:5137
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lock_acquire+0x1ed/0x550 kernel/locking/lockdep.c:5754
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__raw_spin_lock include/linux/spinlock_api_smp.h:133 [inline]
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_raw_spin_lock+0x2e/0x40 kernel/locking/spinlock.c:154
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spin_lock include/linux/spinlock.h:351 [inline]
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__unix_gc+0x40e/0xf70 net/unix/garbage.c:302
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process_one_work kernel/workqueue.c:3254 [inline]
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process_scheduled_works+0xa10/0x17c0 kernel/workqueue.c:3335
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worker_thread+0x86d/0xd70 kernel/workqueue.c:3416
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kthread+0x2f0/0x390 kernel/kthread.c:388
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ret_from_fork+0x4b/0x80 arch/x86/kernel/process.c:147
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ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:244
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other info that might help us debug this:
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Possible unsafe locking scenario:
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CPU0 CPU1
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---- ----
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lock(unix_gc_lock);
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lock(&u->lock);
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lock(unix_gc_lock);
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lock(&u->lock);
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*** DEADLOCK ***
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3 locks held by kworker/u8:1/11:
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#0: ffff888015089148 ((wq_completion)events_unbound){+.+.}-{0:0}, at: process_one_work kernel/workqueue.c:3229 [inline]
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#0: ffff888015089148 ((wq_completion)events_unbound){+.+.}-{0:0}, at: process_scheduled_works+0x8e0/0x17c0 kernel/workqueue.c:3335
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#1: ffffc90000107d00 (unix_gc_work){+.+.}-{0:0}, at: process_one_work kernel/workqueue.c:3230 [inline]
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#1: ffffc90000107d00 (unix_gc_work){+.+.}-{0:0}, at: process_scheduled_works+0x91b/0x17c0 kernel/workqueue.c:3335
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#2: ffffffff8f6ab638 (unix_gc_lock){+.+.}-{2:2}, at: spin_lock include/linux/spinlock.h:351 [inline]
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#2: ffffffff8f6ab638 (unix_gc_lock){+.+.}-{2:2}, at: __unix_gc+0x117/0xf70 net/unix/garbage.c:261
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stack backtrace:
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CPU: 0 PID: 11 Comm: kworker/u8:1 Not tainted 6.9.0-rc5-syzkaller-00007-g4d2008430ce8 #0
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Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 03/27/2024
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Workqueue: events_unbound __unix_gc
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Call Trace:
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<TASK>
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__dump_stack lib/dump_stack.c:88 [inline]
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dump_stack_lvl+0x241/0x360 lib/dump_stack.c:114
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check_noncircular+0x36a/0x4a0 kernel/locking/lockdep.c:2187
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check_prev_add kernel/locking/lockdep.c:3134 [inline]
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check_prevs_add kernel/locking/lockdep.c:3253 [inline]
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validate_chain+0x18cb/0x58e0 kernel/locking/lockdep.c:3869
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__lock_acquire+0x1346/0x1fd0 kernel/locking/lockdep.c:5137
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lock_acquire+0x1ed/0x550 kernel/locking/lockdep.c:5754
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__raw_spin_lock include/linux/spinlock_api_smp.h:133 [inline]
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_raw_spin_lock+0x2e/0x40 kernel/locking/spinlock.c:154
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spin_lock include/linux/spinlock.h:351 [inline]
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__unix_gc+0x40e/0xf70 net/unix/garbage.c:302
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process_one_work kernel/workqueue.c:3254 [inline]
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process_scheduled_works+0xa10/0x17c0 kernel/workqueue.c:3335
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worker_thread+0x86d/0xd70 kernel/workqueue.c:3416
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kthread+0x2f0/0x390 kernel/kthread.c:388
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ret_from_fork+0x4b/0x80 arch/x86/kernel/process.c:147
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ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:244
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</TASK>
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Fixes: 47d8ac011fe1 ("af_unix: Fix garbage collector racing against connect()")
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Reported-and-tested-by: syzbot+fa379358c28cc87cc307@syzkaller.appspotmail.com
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Closes: https://syzkaller.appspot.com/bug?extid=fa379358c28cc87cc307
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Signed-off-by: Kuniyuki Iwashima <kuniyu@amazon.com>
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Link: https://lore.kernel.org/r/20240424170443.9832-1-kuniyu@amazon.com
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Signed-off-by: Jakub Kicinski <kuba@kernel.org>
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(cherry picked from commit 1971d13ffa84a551d29a81fdf5b5ec5be166ac83)
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Signed-off-by: Jonathan Maple <jmaple@ciq.com>
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# Conflicts:
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# net/unix/garbage.c
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diff --cc net/unix/garbage.c
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index 2405f0f9af31,0104be9d4704..000000000000
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--- a/net/unix/garbage.c
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+++ b/net/unix/garbage.c
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@@@ -248,6 -297,11 +248,14 @@@ void unix_gc(void
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list_move_tail(&u->link, &gc_candidates);
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__set_bit(UNIX_GC_CANDIDATE, &u->gc_flags);
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__set_bit(UNIX_GC_MAYBE_CYCLE, &u->gc_flags);
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++<<<<<<< HEAD
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++=======
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+
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+ if (sk->sk_state == TCP_LISTEN) {
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+ unix_state_lock_nested(sk, U_LOCK_GC_LISTENER);
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+ unix_state_unlock(sk);
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+ }
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++>>>>>>> 1971d13ffa84 (af_unix: Suppress false-positive lockdep splat for spin_lock() in __unix_gc().)
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}
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}
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diff --git a/include/net/af_unix.h b/include/net/af_unix.h
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index 8b0dd4b52c1b..3697799f3b0c 100644
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--- a/include/net/af_unix.h
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+++ b/include/net/af_unix.h
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@@ -77,6 +77,9 @@ enum unix_socket_lock_class {
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U_LOCK_NORMAL,
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U_LOCK_SECOND, /* for double locking, see unix_state_double_lock(). */
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U_LOCK_DIAG, /* used while dumping icons, see sk_diag_dump_icons(). */
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+ U_LOCK_GC_LISTENER, /* used for listening socket while determining gc
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+ * candidates to close a small race window.
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+ */
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};
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static inline void unix_state_lock_nested(struct sock *sk,
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* Unmerged path net/unix/garbage.c

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