hulk inclusion category: bugfix bugzilla: https://gitee.com/openeuler/kernel/issues/IBW902 CVE: NA -------------------------------- Inside shrink_lock_dentry(), if we can't lock the parent, we unlock the dentry and wait for the parent lock. Once we get the parent lock, we lock the dentry again. After locking the dentry a second time, we only check d_lockref.count and don't see if d_inode changed. But during that lock gap, d_inode may be modified. If the inode changes, the inode in the dentry isn't locked. However, in dentry_unlink_inode(), we unlock the inode no matter what. Then, we will get the following Oops: ------------[ cut here ]------------ pvqspinlock: lock 0xff438c8e84836be0 has corrupted value 0x0! WARNING: CPU: 1 PID: 370 at kernel/locking/qspinlock_paravirt.h:498 CPU: 1 PID: 370 Comm: bash Not tainted 5.10.0 #2008 RIP: 0010:__pv_queued_spin_unlock_slowpath+0xbf/0xd0 Call Trace: __raw_callee_save___pv_queued_spin_unlock_slowpath+0x11/0x24 .slowpath+0x9/0x16 dentry_unlink_inode+0x91/0x120 __dentry_kill+0xf3/0x1c0 shrink_dentry_list+0x4b/0xe0 prune_dcache_sb+0x52/0x80 super_cache_scan+0x133/0x1f0 do_shrink_slab+0x14a/0x2f0 Here's how concurrency might trigger this issue: P1 | P2 --------------------------------------------- prune_dcache_sb shrink_dentry_list spin_lock(&dentry->d_lock) shrink_lock_dentry /* Negative dentry, therefore no inode to lock. ref 0 */ spin_trylock(&parent->d_lock) / try lock failed / spin_unlock(&dentry->d_lock) lookup_open __d_lookup spin_lock(&dentry->d_lock) dentry->d_lockref.count++ /* ref 1 */ spin_unlock(&dentry->d_lock) /* Negative dentry, just create the file */ xfs_generic_create d_instantiate spin_lock(&inode->i_lock) __d_instantiate spin_lock(&dentry->d_lock) __d_set_inode_and_type dentry->d_inode = inode spin_unlock(&dentry->d_lock) spin_unlock(&inode->i_lock) syscall_exit_to_user_mode /* Task exit. */ __fput dput fast_dput spin_lock(&dentry->d_lock) retain_dentry dentry->d_lockref.count-- /* ref 0 */ spin_unlock(&dentry->d_lock) spin_lock(&parent->d_lock) spin_lock_nested(&dentry->d_lock, DENTRY_D_LOCK_NESTED) /* d_inode has been changed but is not locked. */ __dentry_kill dentry_unlink_inode spin_unlock(&dentry->d_lock) spin_unlock(&inode->i_lock) /* Attempt to unlock an unlocked inode. */ /* WARNING: bad unlock balance in dentry_unlink_inode */ Therefore, add the missing d_inode check to avoid this issue. Fixes: 3b3f09f48ba7 ("get rid of trylock loop in locking dentries on shrink list") Signed-off-by: Baokun Li <libaokun1@huawei.com> --- fs/dcache.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/fs/dcache.c b/fs/dcache.c index 926df08eeb0c..35f82d69d2b9 100644 --- a/fs/dcache.c +++ b/fs/dcache.c @@ -1118,7 +1118,7 @@ static bool shrink_lock_dentry(struct dentry *dentry) goto out; } spin_lock_nested(&dentry->d_lock, DENTRY_D_LOCK_NESTED); - if (likely(!dentry->d_lockref.count)) + if (likely(!dentry->d_lockref.count && inode == dentry->d_inode)) return true; spin_unlock(&parent->d_lock); out: -- 2.46.1