[syzbot] [fs?] WARNING in minix_rename

[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+a65e824272c5f741247d@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>


---
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Forwarded: Re: [syzbot] [fs?] WARNING in minix_rename

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Subject: Re: [syzbot] [fs?] WARNING in minix_rename
Author: richard120310@gmail.com

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

Signed-off-by: I Hsin Cheng <richard120310@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

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Subject: 
Author: jkoolstra@xs4all.nl

#syz test

---
fs/minix/namei.c | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)
diff --git a/fs/minix/namei.c b/fs/minix/namei.c
index 8938536d8d3c..86779a6ec1a7 100644
--- a/fs/minix/namei.c
+++ b/fs/minix/namei.c
@@ -224,7 +224,7 @@ static int minix_rename(struct mnt_idmap *idmap,
err = minix_add_link(new_dentry, old_inode);
if (err)
goto out_dir;
- if (dir_de)
+ if (dir_de && old_dir != new_dir)
inode_inc_link_count(new_dir);
}
@@ -236,7 +236,7 @@ static int minix_rename(struct mnt_idmap *idmap,
if (dir_de) {
err = minix_set_link(dir_de, dir_folio, new_dir);
- if (!err)
+ if (!err && (new_inode || old_dir != new_dir))
inode_dec_link_count(old_dir);
}
out_dir:
-- 
2.51.0

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Subject: 
Author: jkoolstra@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

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Subject: 
Author: jkoolstra@xs4all.nl

#syz test

---

diff --git a/fs/minix/namei.c b/fs/minix/namei.c
index a8d5a7e22b7b..8648d860ef0c 100644
--- a/fs/minix/namei.c
+++ b/fs/minix/namei.c
@@ -218,6 +218,13 @@ static int minix_rename(struct mnt_idmap *idmap,
                if (dir_de && !minix_empty_dir(new_inode))
                        goto out_dir;
 
+               err = -EFSCORRUPTED;
+               if (dir_de && new_inode->i_nlink != 2) {
+                       printk(KERN_CRIT "minix-fs error: directory inode has "
+                              "corrupted nlink");
+                       goto out_dir;
+               }
+
                err = -ENOENT;
                new_de = minix_find_entry(new_dentry, &new_folio);
                if (!new_de)

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Subject: 
Author: jkoolstra@xs4all.nl

#syz test

---
diff --git a/fs/minix/minix.h b/fs/minix/minix.h
index d54273c3c9ff..ce62cb61186d 100644
--- a/fs/minix/minix.h
+++ b/fs/minix/minix.h
@@ -168,4 +168,6 @@ static inline int minix_test_bit(int nr, const void *vaddr)
 
 #endif
 
+#define EFSCORRUPTED   EUCLEAN         /* Filesystem is corrupted */
+
 #endif /* FS_MINIX_H */

diff --git a/fs/minix/namei.c b/fs/minix/namei.c
index a8d5a7e22b7b..8648d860ef0c 100644
--- a/fs/minix/namei.c
+++ b/fs/minix/namei.c
@@ -218,6 +218,13 @@ static int minix_rename(struct mnt_idmap *idmap,
                if (dir_de && !minix_empty_dir(new_inode))
                        goto out_dir;
 
+               err = -EFSCORRUPTED;
+               if (dir_de && new_inode->i_nlink != 2) {
+                       printk(KERN_CRIT "minix-fs error: directory inode has "
+                              "corrupted nlink");
+                       goto out_dir;
+               }
+
                err = -ENOENT;
                new_de = minix_find_entry(new_dentry, &new_folio);
                if (!new_de)

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Subject: 
Author: jkoolstra@xs4all.nl

#syz test

---

diff --git a/fs/minix/minix.h b/fs/minix/minix.h
index d54273c3c9ff..ce62cb61186d 100644
--- a/fs/minix/minix.h
+++ b/fs/minix/minix.h
@@ -168,4 +168,6 @@ static inline int minix_test_bit(int nr, const void *vaddr)
 
 #endif
 
+#define EFSCORRUPTED   EUCLEAN         /* Filesystem is corrupted */
+
 #endif /* FS_MINIX_H */
diff --git a/fs/minix/namei.c b/fs/minix/namei.c
index 8938536d8d3c..493a75eff2c9 100644
--- a/fs/minix/namei.c
+++ b/fs/minix/namei.c
@@ -208,6 +218,13 @@ static int minix_rename(struct mnt_idmap *idmap,
                if (dir_de && !minix_empty_dir(new_inode))
                        goto out_dir;
 
+               err = -EFSCORRUPTED;
+               if (new_inode->i_nlink == 0 || (dir_de && new_inode->i_nlink != 2)) {
+                       printk(KERN_CRIT "minix-fs error: inode (ino: %ld) "
+                              "has corrupted nlink", new_inode->i_ino);
+                       goto out_dir;
+               }
+
                err = -ENOENT;
                new_de = minix_find_entry(new_dentry, &new_folio);
                if (!new_de)

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Subject: 
Author: jkoolstra@xs4all.nl

#syz test

---
diff --git a/fs/minix/minix.h b/fs/minix/minix.h
index d54273c3c9ff..ce62cb61186d 100644
--- a/fs/minix/minix.h
+++ b/fs/minix/minix.h
@@ -168,4 +168,6 @@ static inline int minix_test_bit(int nr, const void *vaddr)
 
 #endif
 
+#define EFSCORRUPTED   EUCLEAN         /* Filesystem is corrupted */
+
 #endif /* FS_MINIX_H */
diff --git a/fs/minix/namei.c b/fs/minix/namei.c
index a8d5a7e22b7b..f18f7474aca4 100644
--- a/fs/minix/namei.c
+++ b/fs/minix/namei.c
@@ -145,6 +145,12 @@ static int minix_unlink(struct inode * dir, struct dentry *dentry)
        struct minix_dir_entry * de;
        int err;
 
+       if (inode->i_nlink < 1) {
+               printk(KERN_CRIT "minix-fs error: inode (ino: %ld) "
+                      "has corrupted nlink", inode->i_ino);
+               return -EFSCORRUPTED;
+       }
+
        de = minix_find_entry(dentry, &folio);
        if (!de)
                return -ENOENT;
@@ -218,6 +224,13 @@ static int minix_rename(struct mnt_idmap *idmap,
                if (dir_de && !minix_empty_dir(new_inode))
                        goto out_dir;
 
+               err = -EFSCORRUPTED;
+               if (new_inode->i_nlink == 0 || (dir_de && new_inode->i_nlink != 2)) {
+                       printk(KERN_CRIT "minix-fs error: inode (ino: %ld) "
+                              "has corrupted nlink", new_inode->i_ino);
+                       goto out_dir;
+               }
+
                err = -ENOENT;
                new_de = minix_find_entry(new_dentry, &new_folio);
                if (!new_de)