* [PATCH v2] locking/lockdep: Zap lock classes even with lock debugging disabled
@ 2019-04-03 23:35 Bart Van Assche
2019-04-04 9:36 ` Peter Zijlstra
2019-04-10 12:13 ` [tip:locking/urgent] " tip-bot for Bart Van Assche
0 siblings, 2 replies; 3+ messages in thread
From: Bart Van Assche @ 2019-04-03 23:35 UTC (permalink / raw)
To: Peter Zijlstra
Cc: Ingo Molnar, Thomas Gleixner, linux-kernel, Bart Van Assche,
Will Deacon, Waiman Long, shenghui
Commit a0b0fd53e1e6 ("locking/lockdep: Free lock classes that are no longer
in use") changed the behavior of lockdep_free_key_range() from
unconditionally zapping lock classes into only zapping lock classes if
debug_lock == true. Not zapping lock classes if debug_lock == false leaves
dangling pointers in several lockdep datastructures, e.g. lock_class::name
in the all_lock_classes list. The shell command "cat /proc/lockdep" causes
the kernel to iterate the all_lock_classes list. Hence the "unable to
handle kernel paging request" issue that Shenghui encountered by running
cat /proc/lockdep. Since the new behavior can cause cat /proc/lockdep to
crash, restore the pre-v5.1 behavior.
This patch avoids that cat /proc/lockdep triggers the following crash
with debug_lock == false:
BUG: unable to handle kernel paging request at fffffbfff40ca448
PGD 13bfde067 P4D 13bfde067 PUD 13bf7a067 PMD 1167d3067 PTE 0
Oops: 0000 [#1] PREEMPT SMP KASAN
CPU: 4 PID: 4529 Comm: cat Tainted: G B W O 5.1.0-rc1-dbg+ #4
Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.10.2-1 04/01/2014
RIP: 0010:__asan_load1+0x28/0x50
Call Trace:
string+0xac/0x180
vsnprintf+0x23e/0x820
seq_vprintf+0x82/0xc0
seq_printf+0x92/0xb0
print_name+0x34/0xb0
l_show+0x184/0x200
seq_read+0x59e/0x6c0
proc_reg_read+0x11f/0x170
__vfs_read+0x4d/0x90
vfs_read+0xc5/0x1f0
ksys_read+0xab/0x130
__x64_sys_read+0x43/0x50
do_syscall_64+0x71/0x210
entry_SYSCALL_64_after_hwframe+0x49/0xbe
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Will Deacon <will.deacon@arm.com>
Cc: Waiman Long <longman@redhat.com>
Cc: shenghui <shhuiw@foxmail.com>
Reported-by: shenghui <shhuiw@foxmail.com>
Fixes: a0b0fd53e1e6 ("locking/lockdep: Free lock classes that are no longer in use") # v5.1-rc1.
Signed-off-by: Bart Van Assche <bvanassche@acm.org>
---
Changes compared to v1:
- Restored lockdep recursion protection.
- Made patch description more detailed.
kernel/locking/lockdep.c | 29 ++++++++++++-----------------
1 file changed, 12 insertions(+), 17 deletions(-)
diff --git a/kernel/locking/lockdep.c b/kernel/locking/lockdep.c
index 34cdcbedda49..e16766ff184b 100644
--- a/kernel/locking/lockdep.c
+++ b/kernel/locking/lockdep.c
@@ -4689,8 +4689,8 @@ static void free_zapped_rcu(struct rcu_head *ch)
return;
raw_local_irq_save(flags);
- if (!graph_lock())
- goto out_irq;
+ arch_spin_lock(&lockdep_lock);
+ current->lockdep_recursion = 1;
/* closed head */
pf = delayed_free.pf + (delayed_free.index ^ 1);
@@ -4702,8 +4702,8 @@ static void free_zapped_rcu(struct rcu_head *ch)
*/
call_rcu_zapped(delayed_free.pf + delayed_free.index);
- graph_unlock();
-out_irq:
+ current->lockdep_recursion = 0;
+ arch_spin_unlock(&lockdep_lock);
raw_local_irq_restore(flags);
}
@@ -4744,21 +4744,17 @@ static void lockdep_free_key_range_reg(void *start, unsigned long size)
{
struct pending_free *pf;
unsigned long flags;
- int locked;
init_data_structures_once();
raw_local_irq_save(flags);
- locked = graph_lock();
- if (!locked)
- goto out_irq;
-
+ arch_spin_lock(&lockdep_lock);
+ current->lockdep_recursion = 1;
pf = get_pending_free();
__lockdep_free_key_range(pf, start, size);
call_rcu_zapped(pf);
-
- graph_unlock();
-out_irq:
+ current->lockdep_recursion = 0;
+ arch_spin_unlock(&lockdep_lock);
raw_local_irq_restore(flags);
/*
@@ -4911,9 +4907,8 @@ void lockdep_unregister_key(struct lock_class_key *key)
return;
raw_local_irq_save(flags);
- if (!graph_lock())
- goto out_irq;
-
+ arch_spin_lock(&lockdep_lock);
+ current->lockdep_recursion = 1;
pf = get_pending_free();
hlist_for_each_entry_rcu(k, hash_head, hash_entry) {
if (k == key) {
@@ -4925,8 +4920,8 @@ void lockdep_unregister_key(struct lock_class_key *key)
WARN_ON_ONCE(!found);
__lockdep_free_key_range(pf, key, 1);
call_rcu_zapped(pf);
- graph_unlock();
-out_irq:
+ current->lockdep_recursion = 0;
+ arch_spin_unlock(&lockdep_lock);
raw_local_irq_restore(flags);
/* Wait until is_dynamic_key() has finished accessing k->hash_entry. */
--
2.21.0.196.g041f5ea1cf98
^ permalink raw reply related [flat|nested] 3+ messages in thread* Re: [PATCH v2] locking/lockdep: Zap lock classes even with lock debugging disabled
2019-04-03 23:35 [PATCH v2] locking/lockdep: Zap lock classes even with lock debugging disabled Bart Van Assche
@ 2019-04-04 9:36 ` Peter Zijlstra
2019-04-10 12:13 ` [tip:locking/urgent] " tip-bot for Bart Van Assche
1 sibling, 0 replies; 3+ messages in thread
From: Peter Zijlstra @ 2019-04-04 9:36 UTC (permalink / raw)
To: Bart Van Assche
Cc: Ingo Molnar, Thomas Gleixner, linux-kernel, Will Deacon,
Waiman Long, shenghui
On Wed, Apr 03, 2019 at 04:35:52PM -0700, Bart Van Assche wrote:
> Commit a0b0fd53e1e6 ("locking/lockdep: Free lock classes that are no longer
> in use") changed the behavior of lockdep_free_key_range() from
> unconditionally zapping lock classes into only zapping lock classes if
> debug_lock == true. Not zapping lock classes if debug_lock == false leaves
> dangling pointers in several lockdep datastructures, e.g. lock_class::name
> in the all_lock_classes list. The shell command "cat /proc/lockdep" causes
> the kernel to iterate the all_lock_classes list. Hence the "unable to
> handle kernel paging request" issue that Shenghui encountered by running
> cat /proc/lockdep. Since the new behavior can cause cat /proc/lockdep to
> crash, restore the pre-v5.1 behavior.
>
> This patch avoids that cat /proc/lockdep triggers the following crash
> with debug_lock == false:
>
> BUG: unable to handle kernel paging request at fffffbfff40ca448
> PGD 13bfde067 P4D 13bfde067 PUD 13bf7a067 PMD 1167d3067 PTE 0
> Oops: 0000 [#1] PREEMPT SMP KASAN
> CPU: 4 PID: 4529 Comm: cat Tainted: G B W O 5.1.0-rc1-dbg+ #4
> Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.10.2-1 04/01/2014
> RIP: 0010:__asan_load1+0x28/0x50
> Call Trace:
> string+0xac/0x180
> vsnprintf+0x23e/0x820
> seq_vprintf+0x82/0xc0
> seq_printf+0x92/0xb0
> print_name+0x34/0xb0
> l_show+0x184/0x200
> seq_read+0x59e/0x6c0
> proc_reg_read+0x11f/0x170
> __vfs_read+0x4d/0x90
> vfs_read+0xc5/0x1f0
> ksys_read+0xab/0x130
> __x64_sys_read+0x43/0x50
> do_syscall_64+0x71/0x210
> entry_SYSCALL_64_after_hwframe+0x49/0xbe
>
> Cc: Thomas Gleixner <tglx@linutronix.de>
> Cc: Will Deacon <will.deacon@arm.com>
> Cc: Waiman Long <longman@redhat.com>
> Cc: shenghui <shhuiw@foxmail.com>
> Reported-by: shenghui <shhuiw@foxmail.com>
> Fixes: a0b0fd53e1e6 ("locking/lockdep: Free lock classes that are no longer in use") # v5.1-rc1.
> Signed-off-by: Bart Van Assche <bvanassche@acm.org>
Thanks!
^ permalink raw reply [flat|nested] 3+ messages in thread* [tip:locking/urgent] locking/lockdep: Zap lock classes even with lock debugging disabled
2019-04-03 23:35 [PATCH v2] locking/lockdep: Zap lock classes even with lock debugging disabled Bart Van Assche
2019-04-04 9:36 ` Peter Zijlstra
@ 2019-04-10 12:13 ` tip-bot for Bart Van Assche
1 sibling, 0 replies; 3+ messages in thread
From: tip-bot for Bart Van Assche @ 2019-04-10 12:13 UTC (permalink / raw)
To: linux-tip-commits
Cc: shhuiw, tglx, longman, mingo, hpa, bvanassche, peterz,
will.deacon, linux-kernel, torvalds
Commit-ID: 90c1cba2b3b3851c151229f61801919b2904d437
Gitweb: https://git.kernel.org/tip/90c1cba2b3b3851c151229f61801919b2904d437
Author: Bart Van Assche <bvanassche@acm.org>
AuthorDate: Wed, 3 Apr 2019 16:35:52 -0700
Committer: Ingo Molnar <mingo@kernel.org>
CommitDate: Wed, 10 Apr 2019 13:45:59 +0200
locking/lockdep: Zap lock classes even with lock debugging disabled
The following commit:
a0b0fd53e1e6 ("locking/lockdep: Free lock classes that are no longer in use")
changed the behavior of lockdep_free_key_range() from
unconditionally zapping lock classes into only zapping lock classes if
debug_lock == true. Not zapping lock classes if debug_lock == false leaves
dangling pointers in several lockdep datastructures, e.g. lock_class::name
in the all_lock_classes list.
The shell command "cat /proc/lockdep" causes the kernel to iterate the
all_lock_classes list. Hence the "unable to handle kernel paging request" cash
that Shenghui encountered by running cat /proc/lockdep.
Since the new behavior can cause cat /proc/lockdep to crash, restore the
pre-v5.1 behavior.
This patch avoids that cat /proc/lockdep triggers the following crash
with debug_lock == false:
BUG: unable to handle kernel paging request at fffffbfff40ca448
RIP: 0010:__asan_load1+0x28/0x50
Call Trace:
string+0xac/0x180
vsnprintf+0x23e/0x820
seq_vprintf+0x82/0xc0
seq_printf+0x92/0xb0
print_name+0x34/0xb0
l_show+0x184/0x200
seq_read+0x59e/0x6c0
proc_reg_read+0x11f/0x170
__vfs_read+0x4d/0x90
vfs_read+0xc5/0x1f0
ksys_read+0xab/0x130
__x64_sys_read+0x43/0x50
do_syscall_64+0x71/0x210
entry_SYSCALL_64_after_hwframe+0x49/0xbe
Reported-by: shenghui <shhuiw@foxmail.com>
Signed-off-by: Bart Van Assche <bvanassche@acm.org>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Waiman Long <longman@redhat.com>
Cc: Will Deacon <will.deacon@arm.com>
Fixes: a0b0fd53e1e6 ("locking/lockdep: Free lock classes that are no longer in use") # v5.1-rc1.
Link: https://lkml.kernel.org/r/20190403233552.124673-1-bvanassche@acm.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
---
kernel/locking/lockdep.c | 29 ++++++++++++-----------------
1 file changed, 12 insertions(+), 17 deletions(-)
diff --git a/kernel/locking/lockdep.c b/kernel/locking/lockdep.c
index 34cdcbedda49..e16766ff184b 100644
--- a/kernel/locking/lockdep.c
+++ b/kernel/locking/lockdep.c
@@ -4689,8 +4689,8 @@ static void free_zapped_rcu(struct rcu_head *ch)
return;
raw_local_irq_save(flags);
- if (!graph_lock())
- goto out_irq;
+ arch_spin_lock(&lockdep_lock);
+ current->lockdep_recursion = 1;
/* closed head */
pf = delayed_free.pf + (delayed_free.index ^ 1);
@@ -4702,8 +4702,8 @@ static void free_zapped_rcu(struct rcu_head *ch)
*/
call_rcu_zapped(delayed_free.pf + delayed_free.index);
- graph_unlock();
-out_irq:
+ current->lockdep_recursion = 0;
+ arch_spin_unlock(&lockdep_lock);
raw_local_irq_restore(flags);
}
@@ -4744,21 +4744,17 @@ static void lockdep_free_key_range_reg(void *start, unsigned long size)
{
struct pending_free *pf;
unsigned long flags;
- int locked;
init_data_structures_once();
raw_local_irq_save(flags);
- locked = graph_lock();
- if (!locked)
- goto out_irq;
-
+ arch_spin_lock(&lockdep_lock);
+ current->lockdep_recursion = 1;
pf = get_pending_free();
__lockdep_free_key_range(pf, start, size);
call_rcu_zapped(pf);
-
- graph_unlock();
-out_irq:
+ current->lockdep_recursion = 0;
+ arch_spin_unlock(&lockdep_lock);
raw_local_irq_restore(flags);
/*
@@ -4911,9 +4907,8 @@ void lockdep_unregister_key(struct lock_class_key *key)
return;
raw_local_irq_save(flags);
- if (!graph_lock())
- goto out_irq;
-
+ arch_spin_lock(&lockdep_lock);
+ current->lockdep_recursion = 1;
pf = get_pending_free();
hlist_for_each_entry_rcu(k, hash_head, hash_entry) {
if (k == key) {
@@ -4925,8 +4920,8 @@ void lockdep_unregister_key(struct lock_class_key *key)
WARN_ON_ONCE(!found);
__lockdep_free_key_range(pf, key, 1);
call_rcu_zapped(pf);
- graph_unlock();
-out_irq:
+ current->lockdep_recursion = 0;
+ arch_spin_unlock(&lockdep_lock);
raw_local_irq_restore(flags);
/* Wait until is_dynamic_key() has finished accessing k->hash_entry. */
^ permalink raw reply related [flat|nested] 3+ messages in thread
end of thread, other threads:[~2019-04-10 12:13 UTC | newest]
Thread overview: 3+ messages (download: mbox.gz / follow: Atom feed)
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2019-04-03 23:35 [PATCH v2] locking/lockdep: Zap lock classes even with lock debugging disabled Bart Van Assche
2019-04-04 9:36 ` Peter Zijlstra
2019-04-10 12:13 ` [tip:locking/urgent] " tip-bot for Bart Van Assche
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