On Fri, Apr 03, 2020 at 11:11:35AM +0200, Oleg Nesterov wrote: > On 04/02, syzbot wrote: > > > > lock_acquire+0x1f2/0x8f0 kernel/locking/lockdep.c:4923 > > __raw_spin_lock include/linux/spinlock_api_smp.h:142 [inline] > > _raw_spin_lock+0x2a/0x40 kernel/locking/spinlock.c:151 > > spin_lock include/linux/spinlock.h:353 [inline] > > proc_pid_make_inode+0x1f9/0x3c0 fs/proc/base.c:1880 > > Yes, spin_lock(wait_pidfd.lock) is not safe... > > Eric, at first glance the fix is simple. > > Oleg. > > > diff --git a/fs/proc/base.c b/fs/proc/base.c Um, when did this lock get added to proc/base.c in the first place and why has it been abused for this? People just recently complained loudly about this in the cred_guard_mutex thread that abusing locks for things they weren't intended for is a bad idea... > index 74f948a6b621..9ec8c114aa60 100644 > --- a/fs/proc/base.c > +++ b/fs/proc/base.c > @@ -1839,9 +1839,9 @@ void proc_pid_evict_inode(struct proc_inode *ei) > struct pid *pid = ei->pid; > > if (S_ISDIR(ei->vfs_inode.i_mode)) { > - spin_lock(&pid->wait_pidfd.lock); > + spin_lock_irq(&pid->wait_pidfd.lock); > hlist_del_init_rcu(&ei->sibling_inodes); > - spin_unlock(&pid->wait_pidfd.lock); > + spin_unlock_irq(&pid->wait_pidfd.lock); > } > > put_pid(pid); > @@ -1877,9 +1877,9 @@ struct inode *proc_pid_make_inode(struct super_block * sb, > /* Let the pid remember us for quick removal */ > ei->pid = pid; > if (S_ISDIR(mode)) { > - spin_lock(&pid->wait_pidfd.lock); > + spin_lock_irq(&pid->wait_pidfd.lock); > hlist_add_head_rcu(&ei->sibling_inodes, &pid->inodes); > - spin_unlock(&pid->wait_pidfd.lock); > + spin_unlock_irq(&pid->wait_pidfd.lock); > } > > task_dump_owner(task, 0, &inode->i_uid, &inode->i_gid); > diff --git a/fs/proc/inode.c b/fs/proc/inode.c > index 1e730ea1dcd6..6b7ee76e1b36 100644 > --- a/fs/proc/inode.c > +++ b/fs/proc/inode.c > @@ -123,9 +123,9 @@ void proc_invalidate_siblings_dcache(struct hlist_head *inodes, spinlock_t *lock > if (!node) > break; > ei = hlist_entry(node, struct proc_inode, sibling_inodes); > - spin_lock(lock); > + spin_lock_irq(lock); > hlist_del_init_rcu(&ei->sibling_inodes); > - spin_unlock(lock); > + spin_unlock_irq(lock); > > inode = &ei->vfs_inode; > sb = inode->i_sb; >