Re: [PATCH] selinux: no recursive read_lock of policy_rwlock in security_genfs_sid()

[Waiman Long]

On 06/20/2014 01:49 PM, Stephen Smalley wrote:
> On 06/20/2014 01:45 PM, Waiman Long wrote:
> > With introduction of fair queued rwlock, recursive read_lock() may hang
> > the offending process if there is a write_lock() somewhere in between.
> >
> > With recursive read_lock checking enabled, the following error was
> > reported:
> >
> > =============================================
> > [ INFO: possible recursive locking detected ]
> > 3.16.0-rc1 #2 Tainted: G            E
> > ---------------------------------------------
> > load_policy/708 is trying to acquire lock:
> >   (policy_rwlock){.+.+..}, at: [<ffffffff8125b32a>] security_genfs_sid+0x3a/0x170
> >
> > but task is already holding lock:
> >   (policy_rwlock){.+.+..}, at: [<ffffffff8125b48c>] security_fs_use+0x2c/0x110
> >
> > other info that might help us debug this:
> >   Possible unsafe locking scenario:
> >
> >         CPU0
> >         ----
> >    lock(policy_rwlock);
> >    lock(policy_rwlock);
> >
> > This patch fixes the occurrence of recursive read_lock() of
> > policy_rwlock in security_genfs_sid() by adding a 5th argument to
> > indicate if the rwlock has been taken.
> >
> > Signed-off-by: Waiman Long<Waiman.Long@xxxxxx>
> Thanks, but I'd prefer to instead create a static helper function in
> services.c that does not take the lock at all, use that function from
> security_fs_use, and leave the extern function unmodified.

On second thought, this is exactly what I want to change the patch. I 
will send out a new one later today.

-Longman
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