linux-stable.git/kernel/locking/lockdep.c, branch v5.15.208

locking/lockdep: Decrease nr_unused_locks if lock unused in zap_class()

2025-05-02T05:44:03+00:00

commit 495f53d5cca0f939eaed9dca90b67e7e6fb0e30c upstream.

Currently, when a lock class is allocated, nr_unused_locks will be
increased by 1, until it gets used: nr_unused_locks will be decreased by
1 in mark_lock(). However, one scenario is missed: a lock class may be
zapped without even being used once. This could result into a situation
that nr_unused_locks != 0 but no unused lock class is active in the
system, and when `cat /proc/lockdep_stats`, a WARN_ON() will
be triggered in a CONFIG_DEBUG_LOCKDEP=y kernel:

  [...] DEBUG_LOCKS_WARN_ON(debug_atomic_read(nr_unused_locks) != nr_unused)
  [...] WARNING: CPU: 41 PID: 1121 at kernel/locking/lockdep_proc.c:283 lockdep_stats_show+0xba9/0xbd0

And as a result, lockdep will be disabled after this.

Therefore, nr_unused_locks needs to be accounted correctly at
zap_class() time.

Signed-off-by: Boqun Feng 
Signed-off-by: Ingo Molnar 
Reviewed-by: Waiman Long 
Cc: stable@vger.kernel.org
Link: https://lore.kernel.org/r/20250326180831.510348-1-boqun.feng@gmail.com
Signed-off-by: Greg Kroah-Hartman

lockdep: fix deadlock issue between lockdep and rcu

2024-10-17T13:11:18+00:00

commit a6f88ac32c6e63e69c595bfae220d8641704c9b7 upstream.

There is a deadlock scenario between lockdep and rcu when
rcu nocb feature is enabled, just as following call stack:

     rcuop/x
-000|queued_spin_lock_slowpath(lock = 0xFFFFFF817F2A8A80, val = ?)
-001|queued_spin_lock(inline) // try to hold nocb_gp_lock
-001|do_raw_spin_lock(lock = 0xFFFFFF817F2A8A80)
-002|__raw_spin_lock_irqsave(inline)
-002|_raw_spin_lock_irqsave(lock = 0xFFFFFF817F2A8A80)
-003|wake_nocb_gp_defer(inline)
-003|__call_rcu_nocb_wake(rdp = 0xFFFFFF817F30B680)
-004|__call_rcu_common(inline)
-004|call_rcu(head = 0xFFFFFFC082EECC28, func = ?)
-005|call_rcu_zapped(inline)
-005|free_zapped_rcu(ch = ?)// hold graph lock
-006|rcu_do_batch(rdp = 0xFFFFFF817F245680)
-007|nocb_cb_wait(inline)
-007|rcu_nocb_cb_kthread(arg = 0xFFFFFF817F245680)
-008|kthread(_create = 0xFFFFFF80803122C0)
-009|ret_from_fork(asm)

     rcuop/y
-000|queued_spin_lock_slowpath(lock = 0xFFFFFFC08291BBC8, val = 0)
-001|queued_spin_lock()
-001|lockdep_lock()
-001|graph_lock() // try to hold graph lock
-002|lookup_chain_cache_add()
-002|validate_chain()
-003|lock_acquire
-004|_raw_spin_lock_irqsave(lock = 0xFFFFFF817F211D80)
-005|lock_timer_base(inline)
-006|mod_timer(inline)
-006|wake_nocb_gp_defer(inline)// hold nocb_gp_lock
-006|__call_rcu_nocb_wake(rdp = 0xFFFFFF817F2A8680)
-007|__call_rcu_common(inline)
-007|call_rcu(head = 0xFFFFFFC0822E0B58, func = ?)
-008|call_rcu_hurry(inline)
-008|rcu_sync_call(inline)
-008|rcu_sync_func(rhp = 0xFFFFFFC0822E0B58)
-009|rcu_do_batch(rdp = 0xFFFFFF817F266680)
-010|nocb_cb_wait(inline)
-010|rcu_nocb_cb_kthread(arg = 0xFFFFFF817F266680)
-011|kthread(_create = 0xFFFFFF8080363740)
-012|ret_from_fork(asm)

rcuop/x and rcuop/y are rcu nocb threads with the same nocb gp thread.
This patch release the graph lock before lockdep call_rcu.

Fixes: a0b0fd53e1e6 ("locking/lockdep: Free lock classes that are no longer in use")
Cc: stable@vger.kernel.org
Cc: Boqun Feng 
Cc: Waiman Long 
Cc: Carlos Llamas 
Cc: Bart Van Assche 
Signed-off-by: Zhiguo Niu 
Signed-off-by: Xuewen Yan 
Reviewed-by: Waiman Long 
Reviewed-by: Carlos Llamas 
Reviewed-by: Bart Van Assche 
Signed-off-by: Carlos Llamas 
Acked-by: Paul E. McKenney 
Signed-off-by: Boqun Feng 
Link: https://lore.kernel.org/r/20240620225436.3127927-1-cmllamas@google.com
Signed-off-by: Greg Kroah-Hartman

lockdep: Fix block chain corruption

2023-12-03T06:31:23+00:00

[ Upstream commit bca4104b00fec60be330cd32818dd5c70db3d469 ]

Kent reported an occasional KASAN splat in lockdep. Mark then noted:

> I suspect the dodgy access is to chain_block_buckets[-1], which hits the last 4
> bytes of the redzone and gets (incorrectly/misleadingly) attributed to
> nr_large_chain_blocks.

That would mean @size == 0, at which point size_to_bucket() returns -1
and the above happens.

alloc_chain_hlocks() has 'size - req', for the first with the
precondition 'size >= rq', which allows the 0.

This code is trying to split a block, del_chain_block() takes what we
need, and add_chain_block() puts back the remainder, except in the
above case the remainder is 0 sized and things go sideways.

Fixes: 810507fe6fd5 ("locking/lockdep: Reuse freed chain_hlocks entries")
Reported-by: Kent Overstreet 
Signed-off-by: Peter Zijlstra (Intel) 
Tested-by: Kent Overstreet 
Link: https://lkml.kernel.org/r/20231121114126.GH8262@noisy.programming.kicks-ass.net
Signed-off-by: Sasha Levin

lockdep: Fix -Wunused-parameter for _THIS_IP_

2022-09-20T10:39:42+00:00

[ Upstream commit 8b023accc8df70e72f7704d29fead7ca914d6837 ]

While looking into a bug related to the compiler's handling of addresses
of labels, I noticed some uses of _THIS_IP_ seemed unused in lockdep.
Drive by cleanup.

-Wunused-parameter:
kernel/locking/lockdep.c:1383:22: warning: unused parameter 'ip'
kernel/locking/lockdep.c:4246:48: warning: unused parameter 'ip'
kernel/locking/lockdep.c:4844:19: warning: unused parameter 'ip'

Signed-off-by: Nick Desaulniers 
Signed-off-by: Peter Zijlstra (Intel) 
Acked-by: Waiman Long 
Link: https://lore.kernel.org/r/20220314221909.2027027-1-ndesaulniers@google.com
Stable-dep-of: 54c3931957f6 ("tracing: hold caller_addr to hardirq_{enable,disable}_ip")
Signed-off-by: Sasha Levin

locking/lockdep: Fix lockdep_init_map_*() confusion

2022-08-17T12:23:08+00:00

[ Upstream commit eae6d58d67d9739be5f7ae2dbead1d0ef6528243 ]

Commit dfd5e3f5fe27 ("locking/lockdep: Mark local_lock_t") added yet
another lockdep_init_map_*() variant, but forgot to update all the
existing users of the most complicated version.

This could lead to a loss of lock_type and hence an incorrect report.
Given the relative rarity of both local_lock and these annotations,
this is unlikely to happen in practise, still, best fix things.

Fixes: dfd5e3f5fe27 ("locking/lockdep: Mark local_lock_t")
Signed-off-by: Peter Zijlstra (Intel) 
Link: https://lkml.kernel.org/r/YqyEDtoan20K0CVD@worktop.programming.kicks-ass.net
Signed-off-by: Sasha Levin

locking/lockdep: Iterate lock_classes directly when reading lockdep files

2022-04-08T12:23:57+00:00

[ Upstream commit fb7275acd6fb988313dddd8d3d19efa70d9015ad ]

When dumping lock_classes information via /proc/lockdep, we can't take
the lockdep lock as the lock hold time is indeterminate. Iterating
over all_lock_classes without holding lock can be dangerous as there
is a slight chance that it may branch off to other lists leading to
infinite loop or even access invalid memory if changes are made to
all_lock_classes list in parallel.

To avoid this problem, iteration of lock classes is now done directly
on the lock_classes array itself. The lock_classes_in_use bitmap is
checked to see if the lock class is being used. To avoid iterating
the full array all the times, a new max_lock_class_idx value is added
to track the maximum lock_class index that is currently being used.

We can theoretically take the lockdep lock for iterating all_lock_classes
when other lockdep files (lockdep_stats and lock_stat) are accessed as
the lock hold time will be shorter for them. For consistency, they are
also modified to iterate the lock_classes array directly.

Signed-off-by: Waiman Long 
Signed-off-by: Peter Zijlstra (Intel) 
Link: https://lkml.kernel.org/r/20220211035526.1329503-2-longman@redhat.com
Signed-off-by: Sasha Levin

locking/lockdep: Avoid potential access of invalid memory in lock_class

2022-04-08T12:22:48+00:00

commit 61cc4534b6550997c97a03759ab46b29d44c0017 upstream.

It was found that reading /proc/lockdep after a lockdep splat may
potentially cause an access to freed memory if lockdep_unregister_key()
is called after the splat but before access to /proc/lockdep [1]. This
is due to the fact that graph_lock() call in lockdep_unregister_key()
fails after the clearing of debug_locks by the splat process.

After lockdep_unregister_key() is called, the lock_name may be freed
but the corresponding lock_class structure still have a reference to
it. That invalid memory pointer will then be accessed when /proc/lockdep
is read by a user and a use-after-free (UAF) error will be reported if
KASAN is enabled.

To fix this problem, lockdep_unregister_key() is now modified to always
search for a matching key irrespective of the debug_locks state and
zap the corresponding lock class if a matching one is found.

[1] https://lore.kernel.org/lkml/77f05c15-81b6-bddd-9650-80d5f23fe330@i-love.sakura.ne.jp/

Fixes: 8b39adbee805 ("locking/lockdep: Make lockdep_unregister_key() honor 'debug_locks' again")
Reported-by: Tetsuo Handa 
Signed-off-by: Waiman Long 
Signed-off-by: Peter Zijlstra (Intel) 
Reviewed-by: Bart Van Assche 
Cc: Cheng-Jui Wang 
Link: https://lkml.kernel.org/r/20220103023558.1377055-1-longman@redhat.com
Signed-off-by: Greg Kroah-Hartman

lockdep: Correct lock_classes index mapping

2022-02-23T11:03:22+00:00

commit 28df029d53a2fd80c1b8674d47895648ad26dcfb upstream.

A kernel exception was hit when trying to dump /proc/lockdep_chains after
lockdep report "BUG: MAX_LOCKDEP_CHAIN_HLOCKS too low!":

Unable to handle kernel paging request at virtual address 00054005450e05c3
...
00054005450e05c3] address between user and kernel address ranges
...
pc : [0xffffffece769b3a8] string+0x50/0x10c
lr : [0xffffffece769ac88] vsnprintf+0x468/0x69c
...
 Call trace:
  string+0x50/0x10c
  vsnprintf+0x468/0x69c
  seq_printf+0x8c/0xd8
  print_name+0x64/0xf4
  lc_show+0xb8/0x128
  seq_read_iter+0x3cc/0x5fc
  proc_reg_read_iter+0xdc/0x1d4

The cause of the problem is the function lock_chain_get_class() will
shift lock_classes index by 1, but the index don't need to be shifted
anymore since commit 01bb6f0af992 ("locking/lockdep: Change the range
of class_idx in held_lock struct") already change the index to start
from 0.

The lock_classes[-1] located at chain_hlocks array. When printing
lock_classes[-1] after the chain_hlocks entries are modified, the
exception happened.

The output of lockdep_chains are incorrect due to this problem too.

Fixes: f611e8cf98ec ("lockdep: Take read/write status in consideration when generate chainkey")
Signed-off-by: Cheng Jui Wang 
Signed-off-by: Peter Zijlstra (Intel) 
Reviewed-by: Boqun Feng 
Link: https://lore.kernel.org/r/20220210105011.21712-1-cheng-jui.wang@mediatek.com
Signed-off-by: Greg Kroah-Hartman

lockdep: Let lock_is_held_type() detect recursive read as read

2021-11-18T18:16:23+00:00

[ Upstream commit 2507003a1d10917c9158077bf6030719d02c941e ]

lock_is_held_type(, 1) detects acquired read locks. It only recognized
locks acquired with lock_acquire_shared(). Read locks acquired with
lock_acquire_shared_recursive() are not recognized because a `2' is
stored as the read value.

Rework the check to additionally recognise lock's read value one and two
as a read held lock.

Fixes: e918188611f07 ("locking: More accurate annotations for read_lock()")
Signed-off-by: Sebastian Andrzej Siewior 
Signed-off-by: Peter Zijlstra (Intel) 
Acked-by: Boqun Feng 
Acked-by: Waiman Long 
Link: https://lkml.kernel.org/r/20210903084001.lblecrvz4esl4mrr@linutronix.de
Signed-off-by: Sasha Levin

locking/lockdep: Avoid RCU-induced noinstr fail

2021-11-18T18:16:09+00:00

[ Upstream commit ce0b9c805dd66d5e49fd53ec5415ae398f4c56e6 ]

vmlinux.o: warning: objtool: look_up_lock_class()+0xc7: call to rcu_read_lock_any_held() leaves .noinstr.text section

Signed-off-by: Peter Zijlstra (Intel) 
Link: https://lore.kernel.org/r/20210624095148.311980536@infradead.org
Signed-off-by: Sasha Levin