From: Edward Adam Davis <eadavis@xxxxxx> syzbot reported a WARNING in nilfs_rmdir. [1] Because the inode bitmap is corrupted, an inode with an inode number that should exist as a ".nilfs" file was reassigned by nilfs_mkdir for "file0", causing an inode duplication during execution. And this causes an underflow of i_nlink in rmdir operations. The inode is used twice by the same task to unmount and remove directories ".nilfs" and "file0", it trigger warning in nilfs_rmdir. Avoid to this issue, check i_nlink in nilfs_iget(), if it is 0, it means that this inode has been deleted, and iput is executed to reclaim it. [1] WARNING: CPU: 1 PID: 5824 at fs/inode.c:407 drop_nlink+0xc4/0x110 fs/inode.c:407 ... Call Trace: <TASK> nilfs_rmdir+0x1b0/0x250 fs/nilfs2/namei.c:342 vfs_rmdir+0x3a3/0x510 fs/namei.c:4394 do_rmdir+0x3b5/0x580 fs/namei.c:4453 __do_sys_rmdir fs/namei.c:4472 [inline] __se_sys_rmdir fs/namei.c:4470 [inline] __x64_sys_rmdir+0x47/0x50 fs/namei.c:4470 do_syscall_x64 arch/x86/entry/common.c:52 [inline] do_syscall_64+0xf3/0x230 arch/x86/entry/common.c:83 entry_SYSCALL_64_after_hwframe+0x77/0x7f Reported-by: syzbot+9260555647a5132edd48@xxxxxxxxxxxxxxxxxxxxxxxxx Closes: https://syzkaller.appspot.com/bug?extid=9260555647a5132edd48 Tested-by: syzbot+9260555647a5132edd48@xxxxxxxxxxxxxxxxxxxxxxxxx Signed-off-by: Edward Adam Davis <eadavis@xxxxxx> Fixes: d25006523d0b ("nilfs2: pathname operations") Signed-off-by: Ryusuke Konishi <konishi.ryusuke@xxxxxxxxx> --- Hi Andrew, please apply this as a bug fix. This prevents the link count underflow that can occur when deleting directories in an inconsistent file system, which was recently reported by syzbot. Thanks, Ryusuke Konishi fs/nilfs2/inode.c | 8 +++++++- fs/nilfs2/namei.c | 5 +++++ 2 files changed, 12 insertions(+), 1 deletion(-) diff --git a/fs/nilfs2/inode.c b/fs/nilfs2/inode.c index cf9ba481ae37..b7d4105f37bf 100644 --- a/fs/nilfs2/inode.c +++ b/fs/nilfs2/inode.c @@ -544,8 +544,14 @@ struct inode *nilfs_iget(struct super_block *sb, struct nilfs_root *root, inode = nilfs_iget_locked(sb, root, ino); if (unlikely(!inode)) return ERR_PTR(-ENOMEM); - if (!(inode->i_state & I_NEW)) + + if (!(inode->i_state & I_NEW)) { + if (!inode->i_nlink) { + iput(inode); + return ERR_PTR(-ESTALE); + } return inode; + } err = __nilfs_read_inode(sb, root, ino, inode); if (unlikely(err)) { diff --git a/fs/nilfs2/namei.c b/fs/nilfs2/namei.c index 9b108052d9f7..1d836a5540f3 100644 --- a/fs/nilfs2/namei.c +++ b/fs/nilfs2/namei.c @@ -67,6 +67,11 @@ nilfs_lookup(struct inode *dir, struct dentry *dentry, unsigned int flags) inode = NULL; } else { inode = nilfs_iget(dir->i_sb, NILFS_I(dir)->i_root, ino); + if (inode == ERR_PTR(-ESTALE)) { + nilfs_error(dir->i_sb, + "deleted inode referenced: %lu", ino); + return ERR_PTR(-EIO); + } } return d_splice_alias(inode, dentry); -- 2.43.0
