* Re: [PATCH] Forcing subclasses to have same name pointer as their parent class
[not found] ` <CA+6bSasi4W8zEXu+gqGnpvJpFg0EDeW7fwnFMCqYeFH0hcCGag@mail.gmail.com>
@ 2024-07-08 23:55 ` Boqun Feng
0 siblings, 0 replies; 2+ messages in thread
From: Boqun Feng @ 2024-07-08 23:55 UTC (permalink / raw)
To: ahmed Ehab
Cc: linux-kernel, Peter Zijlstra, Ingo Molnar, Will Deacon,
Waiman Long, linux-ext4, Theodore Ts'o, Andreas Dilger,
syzkaller, Paul E. McKenney
On Tue, Jul 09, 2024 at 02:26:05AM +0300, ahmed Ehab wrote:
> Hi,
> thanks for the great feedback.
>
>
>
>
> * Last but not the least, could you try to add a test case in
> lib/locking-selftest.c to ensure the issue you fixed won't happen
> again? This could be tricky, since you will need to fight against
> the compiler to generate two string literals with the same content.*
> I added a test case, but I am not sure how to run this test file as it
> doesn't seem to be part of the kselftests. I compiled it successfully by
> setting the lock debugging option but couldn't get it to run.
>
My usual approach is: set CONFIG_DEBUG_LOCKING_API_SELFTESTS=y, compile
a kernel, and boot it in qemu, the test result will show in serial log
of the VM. Hope that helps.
Regards,
Boqun
> Regards,
> Ahmed
>
> On Thu, Jul 4, 2024 at 1:46 AM Boqun Feng <boqun.feng@gmail.com> wrote:
>
> > Hi,
> >
> > On Thu, Jul 04, 2024 at 03:32:24AM +0300, botta633 wrote:
> > > Preventing Lockdep_set_subclass from creating a new instance of the
> > > string literal. Hence, we will always have the class->name. This
> > > prevents kernel panics when locking up a lock class while comparing
> > > class locks and class names.
> >
> > Good catch! Thanks.
> >
> > >
> > >
> >
> > Please remove the extra blank line here.
> >
> > > Signed-off-by: botta633 <bottaawesome633@gmail.com>
> >
> > Do you mind putting your real name here? Besides, IIUC, this is fixing:
> >
> > https://syzkaller.appspot.com/bug?extid=7f4a6f7f7051474e40ad
> >
> >
> > , right? If so, there are some more things:
> >
> > * Copy ext4 and syzkaller people, so that you could get more
> > tests.
> >
> > * Since this is a bug fix, could you please figure out which
> > commit introduces the issue, so that you can put a correct
> > "Fixes:" tag along with your signed-off-by?
> >
> > * Since the issue was reported by syzkaller, you should put their
> > "Reported-by" tag, they have an example in the website I paste
> > above.
> >
> > * Please also Cc stable mail list so that the fix can be
> > backported, you can find the information on "Cc: stable" tag at:
> >
> > https://docs.kernel.org/process/stable-kernel-rules.html
> >
> > * Last but not the least, could you try to add a test case in
> > lib/locking-selftest.c to ensure the issue you fixed won't
> > happen again? This could be tricky, since you will need to fight
> > against the compiler to generate two string literals with the
> > same content.
> >
> > [Cc ext4 and syzkaller]
> >
> > Regards,
> > Boqun
> >
> > > ---
> > > 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
> > >
> >
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