[syzbot] [fs?] WARNING in minix_rename

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: 78f4e737a53e Merge tag 'for-6.16/dm-fixes' of git://git.ke..
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=10b29182580000
kernel config: https://syzkaller.appspot.com/x/.config?x=28cc6f051378bb16
dashboard link: https://syzkaller.appspot.com/bug?extid=a65e824272c5f741247d
compiler: Debian clang version 20.1.6 (++20250514063057+1e4d39e07757-1~exp1~20250514183223.118), Debian LLD 20.1.6
syz repro: https://syzkaller.appspot.com/x/repro.syz?x=1446370c580000

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/560a423a60ad/disk-78f4e737.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/9e97e18d85b9/vmlinux-78f4e737.xz
kernel image: https://storage.googleapis.com/syzbot-assets/a147a5a27c6e/bzImage-78f4e737.xz
mounted in repro: https://storage.googleapis.com/syzbot-assets/2c4c332ed1d0/mount_0.gz
fsck result: failed (log: https://syzkaller.appspot.com/x/fsck.log?x=12276b70580000)

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+a65e82...@syzkaller.appspotmail.com

------------[ cut here ]------------
WARNING: CPU: 0 PID: 6388 at fs/inode.c:417 drop_nlink+0xc5/0x110 fs/inode.c:417
Modules linked in:
CPU: 0 UID: 0 PID: 6388 Comm: syz.6.27 Not tainted 6.16.0-rc3-syzkaller-00042-g78f4e737a53e #0 PREEMPT(full)
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 05/07/2025
RIP: 0010:drop_nlink+0xc5/0x110 fs/inode.c:417
Code: 78 07 00 00 be 08 00 00 00 e8 c7 35 e8 ff f0 48 ff 83 78 07 00 00 5b 41 5c 41 5e 41 5f 5d e9 42 01 29 09 cc e8 fc da 86 ff 90 <0f> 0b 90 eb 81 44 89 f1 80 e1 07 80 c1 03 38 c1 0f 8c 5b ff ff ff
RSP: 0018:ffffc900030c7a30 EFLAGS: 00010293
RAX: ffffffff82397124 RBX: ffff888055405aa8 RCX: ffff88802da29e00
RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000000000
RBP: 0000000000000000 R08: ffffffff8f9fe1f7 R09: 1ffffffff1f3fc3e
R10: dffffc0000000000 R11: fffffbfff1f3fc3f R12: 1ffff1100aa80b5e
R13: 0000000000000000 R14: ffff888055405af0 R15: dffffc0000000000
FS: 00007fb57180a6c0(0000) GS:ffff888125c83000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007fb571809f98 CR3: 0000000032278000 CR4: 00000000003526f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
<TASK>
inode_dec_link_count include/linux/fs.h:2634 [inline]
minix_rename+0x3cf/0x700 fs/minix/namei.c:222
vfs_rename+0xb99/0xec0 fs/namei.c:5137
do_renameat2+0x878/0xc50 fs/namei.c:5286
__do_sys_rename fs/namei.c:5333 [inline]
__se_sys_rename fs/namei.c:5331 [inline]
__x64_sys_rename+0x82/0x90 fs/namei.c:5331
do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
do_syscall_64+0xfa/0x3b0 arch/x86/entry/syscall_64.c:94
entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7fb57098e929
Code: ff ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 40 00 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 c7 c1 a8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007fb57180a038 EFLAGS: 00000246 ORIG_RAX: 0000000000000052
RAX: ffffffffffffffda RBX: 00007fb570bb6080 RCX: 00007fb57098e929
RDX: 0000000000000000 RSI: 00002000000001c0 RDI: 0000200000001980
RBP: 00007fb570a10b39 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 0000000000000001 R14: 00007fb570bb6080 R15: 00007fffa5abc5a8
</TASK>


---
This report is generated by a bot. It may contain errors.
See https://goo.gl/tpsmEJ for more information about syzbot.
syzbot engineers can be reached at syzk...@googlegroups.com.

syzbot will keep track of this issue. See:
https://goo.gl/tpsmEJ#status for how to communicate with syzbot.

If the report is already addressed, let syzbot know by replying with:
#syz fix: exact-commit-title

If you want syzbot to run the reproducer, reply with:
#syz test: git://repo/address.git branch-or-commit-hash
If you attach or paste a git patch, syzbot will apply it before testing.

If you want to overwrite report's subsystems, reply with:
#syz set subsystems: new-subsystem
(See the list of subsystem names on the web dashboard)

If the report is a duplicate of another one, reply with:
#syz dup: exact-subject-of-another-report

If you want to undo deduplication, reply with:
#syz undup

[I Hsin Cheng]

#syz test: git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git 78f4e737a53e

Signed-off-by: I Hsin Cheng <richar...@gmail.com>
---
fs/minix/namei.c | 7 ++++++-
1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/fs/minix/namei.c b/fs/minix/namei.c
index 8938536d8d3c..4dfbbfd905d8 100644
--- a/fs/minix/namei.c
+++ b/fs/minix/namei.c
@@ -217,8 +217,13 @@ static int minix_rename(struct mnt_idmap *idmap,
if (err)
goto out_dir;
inode_set_ctime_current(new_inode);
- if (dir_de)
+ if (dir_de) {
drop_nlink(new_inode);
+ if (new_inode->i_nlink == 0) {
+ err = -ESTALE;
+ goto out_dir;
+ }
+ }
inode_dec_link_count(new_inode);
} else {
err = minix_add_link(new_dentry, old_inode);
--
2.43.0

[syzbot]

Hello,

syzbot has tested the proposed patch but the reproducer is still triggering an issue:
WARNING in minix_rename

------------[ cut here ]------------
WARNING: CPU: 1 PID: 6941 at fs/inode.c:417 drop_nlink+0xc5/0x110 fs/inode.c:417
Modules linked in:
CPU: 1 UID: 0 PID: 6941 Comm: syz.1.17 Not tainted 6.16.0-rc3-syzkaller-00042-g78f4e737a53e-dirty #0 PREEMPT(full)

Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 05/07/2025
RIP: 0010:drop_nlink+0xc5/0x110 fs/inode.c:417
Code: 78 07 00 00 be 08 00 00 00 e8 c7 35 e8 ff f0 48 ff 83 78 07 00 00 5b 41 5c 41 5e 41 5f 5d e9 42 01 29 09 cc e8 fc da 86 ff 90 <0f> 0b 90 eb 81 44 89 f1 80 e1 07 80 c1 03 38 c1 0f 8c 5b ff ff ff

RSP: 0018:ffffc900037afa30 EFLAGS: 00010293
RAX: ffffffff82397124 RBX: ffff888058536fc8 RCX: ffff88805e4e1e00

RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000000000
RBP: 0000000000000000 R08: ffffffff8f9fe1f7 R09: 1ffffffff1f3fc3e

R10: dffffc0000000000 R11: fffffbfff1f3fc3f R12: 1ffff1100b0a6e02
R13: ffff888058536fc8 R14: ffff888058537010 R15: dffffc0000000000
FS: 00007f6555c806c0(0000) GS:ffff888125d83000(0000) knlGS:0000000000000000

CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033

CR2: 00007fd2e9a57000 CR3: 0000000031f34000 CR4: 00000000003526f0

DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
<TASK>
inode_dec_link_count include/linux/fs.h:2634 [inline]

minix_rename+0x41d/0x780 fs/minix/namei.c:227

vfs_rename+0xb99/0xec0 fs/namei.c:5137
do_renameat2+0x878/0xc50 fs/namei.c:5286
__do_sys_rename fs/namei.c:5333 [inline]
__se_sys_rename fs/namei.c:5331 [inline]
__x64_sys_rename+0x82/0x90 fs/namei.c:5331
do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
do_syscall_64+0xfa/0x3b0 arch/x86/entry/syscall_64.c:94
entry_SYSCALL_64_after_hwframe+0x77/0x7f

RIP: 0033:0x7f6554d8e929

Code: ff ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 40 00 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 c7 c1 a8 ff ff ff f7 d8 64 89 01 48

RSP: 002b:00007f6555c80038 EFLAGS: 00000246 ORIG_RAX: 0000000000000052
RAX: ffffffffffffffda RBX: 00007f6554fb6080 RCX: 00007f6554d8e929

RDX: 0000000000000000 RSI: 00002000000001c0 RDI: 0000200000001980

RBP: 00007f6554e10b39 R08: 0000000000000000 R09: 0000000000000000

R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000

R13: 0000000000000001 R14: 00007f6554fb6080 R15: 00007ffd76fa1978
</TASK>


Tested on:

commit: 78f4e737 Merge tag 'for-6.16/dm-fixes' of git://git.ke..
git tree: git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
console output: https://syzkaller.appspot.com/x/log.txt?x=1619b382580000
kernel config: https://syzkaller.appspot.com/x/.config?x=296f8ec27963edb9
dashboard link: https://syzkaller.appspot.com/bug?extid=a65e824272c5f741247d
compiler: Debian clang version 20.1.7 (++20250616065708+6146a88f6049-1~exp1~20250616065826.132), Debian LLD 20.1.7
patch: https://syzkaller.appspot.com/x/patch.diff?x=11f1b382580000

[syzbot]

For archival purposes, forwarding an incoming command email to
linux-...@vger.kernel.org, syzkall...@googlegroups.com.

***

Subject:
Author: jkoo...@xs4all.nl

#syz test

---
fs/minix/inode.c | 14 ++++++++++++++
fs/minix/namei.c | 22 ++++++++++++++--------
2 files changed, 28 insertions(+), 8 deletions(-)

diff --git a/fs/minix/inode.c b/fs/minix/inode.c
index f007e389d5d2..e27907fc9bf2 100644
--- a/fs/minix/inode.c
+++ b/fs/minix/inode.c
@@ -517,6 +517,13 @@ static struct inode *V1_minix_iget(struct inode *inode)
iget_failed(inode);
return ERR_PTR(-ESTALE);
}
+ if (S_ISDIR(raw_inode->i_mode) && raw_inode->i_nlinks == 1) {
+ printk("MINIX-fs: directory inode (%lu) has single i_nlink\n",
+ inode->i_ino);
+ brelse(bh);
+ iget_failed(inode);
+ return ERR_PTR(-EIO);
+ }
inode->i_mode = raw_inode->i_mode;
i_uid_write(inode, raw_inode->i_uid);
i_gid_write(inode, raw_inode->i_gid);
@@ -555,6 +562,13 @@ static struct inode *V2_minix_iget(struct inode *inode)
iget_failed(inode);
return ERR_PTR(-ESTALE);
}
+ if (S_ISDIR(raw_inode->i_mode) && raw_inode->i_nlinks == 1) {
+ printk("MINIX-fs: directory inode (%lu) has single i_nlink\n",
+ inode->i_ino);
+ brelse(bh);
+ iget_failed(inode);
+ return ERR_PTR(-EIO);
+ }
inode->i_mode = raw_inode->i_mode;
i_uid_write(inode, raw_inode->i_uid);
i_gid_write(inode, raw_inode->i_gid);
diff --git a/fs/minix/namei.c b/fs/minix/namei.c
index 8938536d8d3c..8297ee6651a1 100644
--- a/fs/minix/namei.c
+++ b/fs/minix/namei.c
@@ -161,15 +161,21 @@ static int minix_unlink(struct inode * dir, struct dentry *dentry)
static int minix_rmdir(struct inode * dir, struct dentry *dentry)
{
struct inode * inode = d_inode(dentry);
- int err = -ENOTEMPTY;
-
- if (minix_empty_dir(inode)) {
- err = minix_unlink(dir, dentry);
- if (!err) {
- inode_dec_link_count(dir);
- inode_dec_link_count(inode);
- }
+ int err = -EIO;
+
+ if (dir->i_nlink <= 2)
+ goto out;
+
+ err = -ENOTEMPTY;
+ if (!minix_empty_dir(inode))
+ goto out;
+
+ err = minix_unlink(dir, dentry);
+ if (!err) {
+ inode_dec_link_count(dir);
+ inode_dec_link_count(inode);
}
+out:
return err;
}

--
2.51.0