On Sun, Dec 8, 2024 at 3:00 PM Edward Adam Davis wrote: > > 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 > Modules linked in: > CPU: 1 UID: 0 PID: 5824 Comm: syz-executor223 Not tainted 6.12.0-syzkaller-12113-gbcc8eda6d349 #0 > Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 09/13/2024 > RIP: 0010:drop_nlink+0xc4/0x110 fs/inode.c:407 > Code: bb 70 07 00 00 be 08 00 00 00 e8 57 0b e6 ff f0 48 ff 83 70 07 00 00 5b 41 5c 41 5e 41 5f 5d c3 cc cc cc cc e8 9d 4c 7e ff 90 <0f> 0b 90 eb 83 44 89 e1 80 e1 07 80 c1 03 38 c1 0f 8c 5c ff ff ff > RSP: 0018:ffffc900037f7c70 EFLAGS: 00010293 > RAX: ffffffff822124a3 RBX: 1ffff1100e7ae034 RCX: ffff88807cf53c00 > RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000000000 > RBP: 0000000000000000 R08: ffffffff82212423 R09: 1ffff1100f8ba8ee > R10: dffffc0000000000 R11: ffffed100f8ba8ef R12: ffff888073d701a0 > R13: 1ffff1100e79f5c4 R14: ffff888073d70158 R15: dffffc0000000000 > FS: 0000555558d1e480(0000) GS:ffff8880b8700000(0000) knlGS:0000000000000000 > CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 > CR2: 0000555558d37878 CR3: 000000007d920000 CR4: 00000000003526f0 > DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 > DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 > 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> > --- > V1 -> V2: Adjust the patch as suggested by Ryusuke Konishi > V2 -> V3: Modify the input parameters of nilfs_error and split Reported-and-tested_by > > fs/nilfs2/inode.c | 8 +++++++- > fs/nilfs2/namei.c | 5 +++++ > 2 files changed, 12 insertions(+), 1 deletion(-) Thank you for your help. I'll adopt this and send it upstream after running tests that include more than just the reproducer. Thanks, Ryusuke Konishi > > 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); > -- > 2.47.0 >
