[syzbot] [fs?] WARNING in minix_rmdir

[syzbot] [fs?] WARNING in minix_rmdir

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit:    8155b4ef3466 Add linux-next specific files for 20241220
git tree:       linux-next
console+strace: https://syzkaller.appspot.com/x/log.txt?x=115656f8580000
kernel config:  https://syzkaller.appspot.com/x/.config?x=9c90bb7161a56c88
dashboard link: https://syzkaller.appspot.com/bug?extid=4e49728ec1cbaf3b91d2
compiler:       Debian clang version 15.0.6, GNU ld (GNU Binutils for Debian) 2.40
syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=16726edf980000
C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=17535418580000

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/98a974fc662d/disk-8155b4ef.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/2dea9b72f624/vmlinux-8155b4ef.xz
kernel image: https://storage.googleapis.com/syzbot-assets/593a42b9eb34/bzImage-8155b4ef.xz
mounted in repro: https://storage.googleapis.com/syzbot-assets/7d86236cea0c/mount_0.gz

Bisection is inconclusive: the issue happens on the oldest tested release.

bisection log:  https://syzkaller.appspot.com/x/bisect.txt?x=122c7418580000
final oops:     https://syzkaller.appspot.com/x/report.txt?x=112c7418580000
console output: https://syzkaller.appspot.com/x/log.txt?x=162c7418580000

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+4e49728ec1cbaf3b91d2@syzkaller.appspotmail.com

------------[ cut here ]------------
WARNING: CPU: 0 PID: 5830 at fs/inode.c:407 drop_nlink+0xc4/0x110 fs/inode.c:407
Modules linked in:
CPU: 0 UID: 0 PID: 5830 Comm: syz-executor235 Not tainted 6.13.0-rc3-next-20241220-syzkaller #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 87 15 e7 ff f0 48 ff 83 70 07 00 00 5b 41 5c 41 5e 41 5f 5d c3 cc cc cc cc e8 4d 97 80 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:ffffc90003ecfd30 EFLAGS: 00010293
RAX: ffffffff823e8cd3 RBX: 1ffff1100ef7ca0c RCX: ffff88803493bc00
RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000000000
RBP: 0000000000000000 R08: ffffffff823e8c53 R09: 1ffffffff203563e
R10: dffffc0000000000 R11: fffffbfff203563f R12: ffff888077be5060
R13: ffff8880792a5a70 R14: ffff888077be5018 R15: dffffc0000000000
FS:  0000555592c31380(0000) GS:ffff8880b8600000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007ffe52599f9c CR3: 0000000076e2e000 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:2567 [inline]
 minix_rmdir+0xa5/0xc0 fs/minix/namei.c:170
 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
RIP: 0033:0x7fb0206e3d47
Code: 73 01 c3 48 c7 c1 b8 ff ff ff f7 d8 64 89 01 48 83 c8 ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 44 00 00 b8 54 00 00 00 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 c7 c1 b8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007ffe52599f88 EFLAGS: 00000207 ORIG_RAX: 0000000000000054
RAX: ffffffffffffffda RBX: 0000000000000000 RCX: 00007fb0206e3d47
RDX: 0000000000008890 RSI: 0000000000000000 RDI: 00007ffe5259b130
RBP: 0000000000000065 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000100 R11: 0000000000000207 R12: 00007ffe5259b130
R13: 0000555592c42740 R14: 431bde82d7b634db R15: 00007ffe5259d2b0
 </TASK>


---
This report is generated by a bot. It may contain errors.
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syzbot engineers can be reached at syzkaller@googlegroups.com.

syzbot will keep track of this issue. See:
https://goo.gl/tpsmEJ#status for how to communicate with syzbot.
For information about bisection process see: https://goo.gl/tpsmEJ#bisection

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

Forwarded:

[syzbot]

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

***

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

Forwarded:

[syzbot]

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

***

Subject: 
Author: jkoolstra@xs4all.nl

#syz test

---
 fs/minix/minix.h |  2 ++
 fs/minix/namei.c | 26 ++++++++++++++++++--------
 2 files changed, 20 insertions(+), 8 deletions(-)

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..a8d5a7e22b7b 100644
--- a/fs/minix/namei.c
+++ b/fs/minix/namei.c
@@ -161,15 +161,25 @@ 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 = -EFSCORRUPTED;
+
+	if (dir->i_nlink <= 2) {
+		printk(KERN_CRIT "minix-fs error: directory inode has "
+		       "corrupted nlink");
+		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;
 }
 
-- 
2.51.1.dirty

Re: [syzbot] [fs?] WARNING in minix_rmdir

[syzbot]

Hello,

syzbot has tested the proposed patch and the reproducer did not trigger any issue:

Reported-by: syzbot+4e49728ec1cbaf3b91d2@syzkaller.appspotmail.com
Tested-by: syzbot+4e49728ec1cbaf3b91d2@syzkaller.appspotmail.com

Tested on:

commit:         691d401c Merge tag 'spi-fix-v6.18-rc3' of git://git.ke..
git tree:       upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=14f9a342580000
kernel config:  https://syzkaller.appspot.com/x/.config?x=4217fdec651c5f4e
dashboard link: https://syzkaller.appspot.com/bug?extid=4e49728ec1cbaf3b91d2
compiler:       Debian clang version 20.1.8 (++20250708063551+0c9f909b7976-1~exp1~20250708183702.136), Debian LLD 20.1.8
patch:          https://syzkaller.appspot.com/x/patch.diff?x=11376e14580000

Note: testing is done by a robot and is best-effort only.

Re: [syzbot] [fs?] WARNING in minix_rmdir

[syzbot]

Hello,

syzbot has tested the proposed patch and the reproducer did not trigger any issue:

Reported-by: syzbot+4e49728ec1cbaf3b91d2@syzkaller.appspotmail.com
Tested-by: syzbot+4e49728ec1cbaf3b91d2@syzkaller.appspotmail.com

Tested on:

commit:         3a866087 Linux 6.18-rc1
git tree:       upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=16c7e52f980000
kernel config:  https://syzkaller.appspot.com/x/.config?x=69c57c2b3206cecb
dashboard link: https://syzkaller.appspot.com/bug?extid=4e49728ec1cbaf3b91d2
compiler:       Debian clang version 20.1.8 (++20250708063551+0c9f909b7976-1~exp1~20250708183702.136), Debian LLD 20.1.8
patch:          https://syzkaller.appspot.com/x/patch.diff?x=145a5dcd980000

Note: testing is done by a robot and is best-effort only.