[PATCH v2 1/2] ext4: Forcing subclasses to have same name pointer as their parent class

[PATCH v2 1/2] ext4: Forcing subclasses to have same name pointer as their parent class

[botta633]

From: Ahmed Ehab <bottaawesome633@gmail.com>

Preventing lockdep_set_subclass from creating a new instance of the 
string literal. Hence, we will always have the same class->name among
parent and subclasses. This prevents kernel panics when looking up a 
lock class while comparing class locks and class names.

Reported-by: <syzbot+7f4a6f7f7051474e40ad@syzkaller.appspotmail.com>
Fixes: fd5e3f5fe27
Cc: <stable@vger.kernel.org>
Signed-off-by: Ahmed Ehab <bottaawesome633@gmail.com>
---
 include/linux/lockdep.h | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/include/linux/lockdep.h b/include/linux/lockdep.h
index 08b0d1d9d78b..df8fa5929de7 100644
--- a/include/linux/lockdep.h
+++ b/include/linux/lockdep.h
@@ -173,7 +173,7 @@ static inline void lockdep_init_map(struct lockdep_map *lock, const char *name,
 			      (lock)->dep_map.lock_type)
 
 #define lockdep_set_subclass(lock, sub)					\
-	lockdep_init_map_type(&(lock)->dep_map, #lock, (lock)->dep_map.key, sub,\
+	lockdep_init_map_type(&(lock)->dep_map, (lock)->dep_map.name, (lock)->dep_map.key, sub,\
 			      (lock)->dep_map.wait_type_inner,		\
 			      (lock)->dep_map.wait_type_outer,		\
 			      (lock)->dep_map.lock_type)
-- 
2.45.2

[PATCH 2/2] ext4: Testing lock class and subclass got the same name pointer

[botta633]

Checking if the lockdep_map->name will change when setting the subclass.
It shouldn't change so that the lock class and subclass will have the same name


Reported-by: <syzbot+7f4a6f7f7051474e40ad@syzkaller.appspotmail.com>
Fixes: fd5e3f5fe27
Cc: <stable@vger.kernel.org>
Signed-off-by: botta633 <bottaawesome633@gmail.com>
---
 lib/locking-selftest.c | 16 ++++++++++++++++
 1 file changed, 16 insertions(+)

diff --git a/lib/locking-selftest.c b/lib/locking-selftest.c
index 6f6a5fc85b42..1d7885205f36 100644
--- a/lib/locking-selftest.c
+++ b/lib/locking-selftest.c
@@ -2710,12 +2710,24 @@ static void local_lock_3B(void)
 
 }
 
+static void class_subclass_X1_name(void)
+{
+	const char *name_before_subclass = rwsem_X1.dep_map.name;
+	const char *name_after_subclass;
+
+	WARN_ON(!rwsem_X1.dep_map.name);
+	lockdep_set_subclass(&rwsem_X1, 1);
+	WARN_ON(name_before_subclass != name_after_subclass);
+}
+
 static void local_lock_tests(void)
 {
 	printk("  --------------------------------------------------------------------------\n");
 	printk("  | local_lock tests |\n");
 	printk("  ---------------------\n");
 
+	init_class_X(&lock_X1, &rwlock_X1, &mutex_X1, &rwsem_X1);
+
 	print_testname("local_lock inversion  2");
 	dotest(local_lock_2, SUCCESS, LOCKTYPE_LL);
 	pr_cont("\n");
@@ -2727,6 +2739,10 @@ static void local_lock_tests(void)
 	print_testname("local_lock inversion 3B");
 	dotest(local_lock_3B, FAILURE, LOCKTYPE_LL);
 	pr_cont("\n");
+
+	print_testname("Class and subclass");
+	dotest(class_subclass_X1_name, SUCCESS, LOCKTYPE_RWSEM);
+	pr_cont("\n");
 }
 
 static void hardirq_deadlock_softirq_not_deadlock(void)
-- 
2.45.2

Re: [PATCH 2/2] ext4: Testing lock class and subclass got the same name pointer

[Boqun Feng]

On Sun, Jul 14, 2024 at 08:14:27AM +0300, botta633 wrote:

First, the subsystem tag also needs to be "locking/lockdep" or
"lockdep".

> Checking if the lockdep_map->name will change when setting the subclass.
> It shouldn't change so that the lock class and subclass will have the same name
> 

Could you make the commit log wrapped at 75 columns?

> 
> Reported-by: <syzbot+7f4a6f7f7051474e40ad@syzkaller.appspotmail.com>
> Fixes: fd5e3f5fe27
> Cc: <stable@vger.kernel.org>

Since this is only adding test for a bug fix, you don't need to put
these tags here.

> Signed-off-by: botta633 <bottaawesome633@gmail.com>

Again, could you please put your name here?

Also seems that you send two patch #2, one is with the proper version
number "v2", but not in-reply-to the patch #1, the other doesn't have
the correct version number but has the correct "in-reply-to" field.
Could you use the correct version number and "in-reply-to" next time?

> ---
>  lib/locking-selftest.c | 16 ++++++++++++++++
>  1 file changed, 16 insertions(+)
> 
> diff --git a/lib/locking-selftest.c b/lib/locking-selftest.c
> index 6f6a5fc85b42..1d7885205f36 100644
> --- a/lib/locking-selftest.c
> +++ b/lib/locking-selftest.c
> @@ -2710,12 +2710,24 @@ static void local_lock_3B(void)
>  
>  }
>  
> +static void class_subclass_X1_name(void)
> +{
> +	const char *name_before_subclass = rwsem_X1.dep_map.name;
> +	const char *name_after_subclass;
> +
> +	WARN_ON(!rwsem_X1.dep_map.name);
> +	lockdep_set_subclass(&rwsem_X1, 1);
> +	WARN_ON(name_before_subclass != name_after_subclass);

Could you add some comments here explaining your test? For example,
where name_after_subclass gets set?

> +}
> +
>  static void local_lock_tests(void)
>  {

Please don't add this test into another test, you could directly call
your class_subclass_X1_name() (maybe rename it to *_test()) in
lockding_selftest() function.

Besides, make sure you run the test with and without your modification
in patch #1, and confirm this is the test that could verify your fix.

Regards,
Boqun

>  	printk("  --------------------------------------------------------------------------\n");
>  	printk("  | local_lock tests |\n");
>  	printk("  ---------------------\n");
>  
> +	init_class_X(&lock_X1, &rwlock_X1, &mutex_X1, &rwsem_X1);
> +
>  	print_testname("local_lock inversion  2");
>  	dotest(local_lock_2, SUCCESS, LOCKTYPE_LL);
>  	pr_cont("\n");
> @@ -2727,6 +2739,10 @@ static void local_lock_tests(void)
>  	print_testname("local_lock inversion 3B");
>  	dotest(local_lock_3B, FAILURE, LOCKTYPE_LL);
>  	pr_cont("\n");
> +
> +	print_testname("Class and subclass");
> +	dotest(class_subclass_X1_name, SUCCESS, LOCKTYPE_RWSEM);
> +	pr_cont("\n");
>  }
>  
>  static void hardirq_deadlock_softirq_not_deadlock(void)
> -- 
> 2.45.2
> 

Re: [PATCH v2 1/2] ext4: Forcing subclasses to have same name pointer as their parent class

[Waiman Long]

On 7/14/24 01:14, botta633 wrote:
> From: Ahmed Ehab <bottaawesome633@gmail.com>
>
> Preventing lockdep_set_subclass from creating a new instance of the
> string literal. Hence, we will always have the same class->name among
> parent and subclasses. This prevents kernel panics when looking up a
> lock class while comparing class locks and class names.
>
> Reported-by: <syzbot+7f4a6f7f7051474e40ad@syzkaller.appspotmail.com>
> Fixes: fd5e3f5fe27
> Cc: <stable@vger.kernel.org>
> Signed-off-by: Ahmed Ehab <bottaawesome633@gmail.com>
> ---
>   include/linux/lockdep.h | 2 +-
>   1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/include/linux/lockdep.h b/include/linux/lockdep.h
> index 08b0d1d9d78b..df8fa5929de7 100644
> --- a/include/linux/lockdep.h
> +++ b/include/linux/lockdep.h
> @@ -173,7 +173,7 @@ static inline void lockdep_init_map(struct lockdep_map *lock, const char *name,
>   			      (lock)->dep_map.lock_type)
>   
>   #define lockdep_set_subclass(lock, sub)					\
> -	lockdep_init_map_type(&(lock)->dep_map, #lock, (lock)->dep_map.key, sub,\
> +	lockdep_init_map_type(&(lock)->dep_map, (lock)->dep_map.name, (lock)->dep_map.key, sub,\
>   			      (lock)->dep_map.wait_type_inner,		\
>   			      (lock)->dep_map.wait_type_outer,		\
>   			      (lock)->dep_map.lock_type)

ext4 is a filesystem. It has nothing to do with locking/lockdep. Could 
you resend the patches with the proper prefix of "lockdep:" or 
"locking/lockdep:"?

Thanks,
Longman

Re: [PATCH v2 1/2] ext4: Forcing subclasses to have same name pointer as their parent class

[Boqun Feng]

On Mon, Jul 15, 2024 at 12:39:45AM +0300, ahmed Ehab wrote:
> Ok, I will.
> I just put ext4 because the syzkaller bug was mentioned in the ext4
> subsystem.
> Thanks,
> Ahmed
> 

Please avoid top-posting. And 

> On Mon, Jul 15, 2024 at 12:22 AM Waiman Long <longman@redhat.com> wrote:
> 
> > On 7/14/24 01:14, botta633 wrote:
> > > From: Ahmed Ehab <bottaawesome633@gmail.com>
> > >
> > > Preventing lockdep_set_subclass from creating a new instance of the
> > > string literal. Hence, we will always have the same class->name among
> > > parent and subclasses. This prevents kernel panics when looking up a
> > > lock class while comparing class locks and class names.
> > >
> > > Reported-by: <syzbot+7f4a6f7f7051474e40ad@syzkaller.appspotmail.com>
> > > Fixes: fd5e3f5fe27

please add the title of the commit here as well, e.g.

Fixes: <sha1> ("<title>")

see

	https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=f7ce5eb2cb7993e4417642ac28713a063123461f	

for example.

Regards,
Boqun

> > > Cc: <stable@vger.kernel.org>
> > > Signed-off-by: Ahmed Ehab <bottaawesome633@gmail.com>
> > > ---
> > >   include/linux/lockdep.h | 2 +-
> > >   1 file changed, 1 insertion(+), 1 deletion(-)
> > >
> > > diff --git a/include/linux/lockdep.h b/include/linux/lockdep.h
> > > index 08b0d1d9d78b..df8fa5929de7 100644
> > > --- a/include/linux/lockdep.h
> > > +++ b/include/linux/lockdep.h
> > > @@ -173,7 +173,7 @@ static inline void lockdep_init_map(struct
> > lockdep_map *lock, const char *name,
> > >                             (lock)->dep_map.lock_type)
> > >
> > >   #define lockdep_set_subclass(lock, sub)
> >      \
> > > -     lockdep_init_map_type(&(lock)->dep_map, #lock,
> > (lock)->dep_map.key, sub,\
> > > +     lockdep_init_map_type(&(lock)->dep_map, (lock)->dep_map.name,
> > (lock)->dep_map.key, sub,\
> > >                             (lock)->dep_map.wait_type_inner,          \
> > >                             (lock)->dep_map.wait_type_outer,          \
> > >                             (lock)->dep_map.lock_type)
> >
> > ext4 is a filesystem. It has nothing to do with locking/lockdep. Could
> > you resend the patches with the proper prefix of "lockdep:" or
> > "locking/lockdep:"?
> >
> > Thanks,
> > Longman
> >
> >