[syzbot] [gfs2?] WARNING in chown_common

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: 98906f9d850e Merge tag 'rtc-6.18' of git://git.kernel.org/..
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=10e10c58580000
kernel config: https://syzkaller.appspot.com/x/.config?x=c2d7b4143707d3a0
dashboard link: https://syzkaller.appspot.com/bug?extid=04c2672c56fbb9401640
compiler: Debian clang version 20.1.8 (++20250708063551+0c9f909b7976-1~exp1~20250708183702.136), Debian LLD 20.1.8
syz repro: https://syzkaller.appspot.com/x/repro.syz?x=11ab9b34580000
C reproducer: https://syzkaller.appspot.com/x/repro.c?x=14e10c58580000

Downloadable assets:
disk image (non-bootable): https://storage.googleapis.com/syzbot-assets/d900f083ada3/non_bootable_disk-98906f9d.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/d82186923244/vmlinux-98906f9d.xz
kernel image: https://storage.googleapis.com/syzbot-assets/a23e980d2d8e/bzImage-98906f9d.xz
mounted in repro #1: https://storage.googleapis.com/syzbot-assets/b2d6dc77aff3/mount_2.gz
fsck result: OK (log: https://syzkaller.appspot.com/x/fsck.log?x=13e03892580000)
mounted in repro #2: https://storage.googleapis.com/syzbot-assets/96cd0ec46a20/mount_8.gz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+04c267...@syzkaller.appspotmail.com

DEBUG_RWSEMS_WARN_ON((rwsem_owner(sem) != current) && !rwsem_test_oflags(sem, RWSEM_NONSPINNABLE)): count = 0x0, magic = 0xffff888036665058, owner = 0x0, curr 0xffff88803e332480, list empty
WARNING: CPU: 0 PID: 5699 at kernel/locking/rwsem.c:1381 __up_write kernel/locking/rwsem.c:1380 [inline]
WARNING: CPU: 0 PID: 5699 at kernel/locking/rwsem.c:1381 up_write+0x3a2/0x420 kernel/locking/rwsem.c:1643
Modules linked in:
CPU: 0 UID: 0 PID: 5699 Comm: syz.0.17 Not tainted syzkaller #0 PREEMPT(full)
Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.3-debian-1.16.3-2~bpo12+1 04/01/2014
RIP: 0010:__up_write kernel/locking/rwsem.c:1380 [inline]
RIP: 0010:up_write+0x3a2/0x420 kernel/locking/rwsem.c:1643
Code: d0 48 c7 c7 20 ff 6a 8b 48 c7 c6 40 01 6b 8b 48 8b 14 24 4c 89 f1 4d 89 e0 4c 8b 4c 24 08 41 52 e8 b3 36 e6 ff 48 83 c4 08 90 <0f> 0b 90 90 e9 6d fd ff ff 48 c7 c1 94 61 9e 8f 80 e1 07 80 c1 03
RSP: 0018:ffffc9000d4b7c30 EFLAGS: 00010296
RAX: e0ff97a6af656400 RBX: ffff888036665058 RCX: ffff88803e332480
RDX: 0000000000000000 RSI: 0000000000000001 RDI: 0000000000000002
RBP: dffffc0000000000 R08: 0000000000000003 R09: 0000000000000004
R10: dffffc0000000000 R11: fffffbfff1bfa650 R12: 0000000000000000
R13: ffff8880366650b0 R14: ffff888036665058 R15: 1ffff11006ccca0c
FS: 00007f2b1bd9b6c0(0000) GS:ffff88808d301000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007f63d120f000 CR3: 000000004fe06000 CR4: 0000000000352ef0
Call Trace:
<TASK>
inode_unlock include/linux/fs.h:990 [inline]
chown_common+0x418/0x5c0 fs/open.c:793
do_fchownat+0x161/0x270 fs/open.c:822
__do_sys_lchown fs/open.c:847 [inline]
__se_sys_lchown fs/open.c:845 [inline]
__x64_sys_lchown+0x85/0xa0 fs/open.c:845
do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
do_syscall_64+0xfa/0xfa0 arch/x86/entry/syscall_64.c:94
entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7f2b1c78eec9
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:00007f2b1bd9b038 EFLAGS: 00000246 ORIG_RAX: 000000000000005e
RAX: ffffffffffffffda RBX: 00007f2b1c9e6360 RCX: 00007f2b1c78eec9
RDX: 000000000000ee01 RSI: 0000000000000000 RDI: 00002000000006c0
RBP: 00007f2b1c811f91 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f2b1c9e63f8 R14: 00007f2b1c9e6360 R15: 00007ffe60c7e2c8
</TASK>


---
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If the report is already addressed, let syzbot know by replying with:
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If you want syzbot to run the reproducer, reply with:
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[syzbot]

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

***

Subject: [PATCH] fs: fix stale inode access in chown_common() retry path
Author: karti...@gmail.com

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

When chown_common() retries due to delegation, it reuses the inode
pointer fetched before the retry_deleg label. However, break_deleg_wait()
can cause the dentry to be updated, making path->dentry->d_inode point
to a different inode. The stale inode pointer leads to locking/unlocking
an invalid or freed inode, triggering a rwsem warning.

The issue manifests as:

WARNING: CPU: 0 PID: 5699 at kernel/locking/rwsem.c:1381 up_write+0x3a2/0x420

DEBUG_RWSEMS_WARN_ON((rwsem_owner(sem) != current) &&
!rwsem_test_oflags(sem, RWSEM_NONSPINNABLE)):

count = 0x0, owner = 0x0

Fix by refreshing both the inode pointer and its associated filesystem
user namespace on each retry iteration, ensuring operations are always
performed on the current, valid inode.

Reported-by: syzbot+04c267...@syzkaller.appspotmail.com
Closes: https://syzkaller.appspot.com/bug?extid=04c2672c56fbb9401640
Signed-off-by: Deepanshu Kartikey <karti...@gmail.com>
---
fs/open.c | 5 +++--
1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/fs/open.c b/fs/open.c
index 3d64372ecc67..8672072fb4c1 100644
--- a/fs/open.c
+++ b/fs/open.c
@@ -755,7 +755,7 @@ int chown_common(const struct path *path, uid_t user, gid_t group)
{
struct mnt_idmap *idmap;
struct user_namespace *fs_userns;
- struct inode *inode = path->dentry->d_inode;
+ struct inode *inode;
struct inode *delegated_inode = NULL;
int error;
struct iattr newattrs;
@@ -766,9 +766,10 @@ int chown_common(const struct path *path, uid_t user, gid_t group)
gid = make_kgid(current_user_ns(), group);

idmap = mnt_idmap(path->mnt);
- fs_userns = i_user_ns(inode);

retry_deleg:
+ inode = path->dentry->d_inode;
+ fs_userns = i_user_ns(inode);
newattrs.ia_vfsuid = INVALID_VFSUID;
newattrs.ia_vfsgid = INVALID_VFSGID;
newattrs.ia_valid = ATTR_CTIME;
--
2.34.1

[syzbot]

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

***

Subject: [PATCH] fs: fix stale inode access in chown_common() retry path
Author: karti...@gmail.com

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

When chown_common() retries due to delegation, it reuses the inode
pointer fetched before the retry_deleg label. However, break_deleg_wait()
can cause the dentry to be updated, making path->dentry->d_inode point
to a different inode. The stale inode pointer leads to locking/unlocking
an invalid or freed inode, triggering a rwsem warning.

The issue manifests as:

WARNING: CPU: 0 PID: 5699 at kernel/locking/rwsem.c:1381 up_write+0x3a2/0x420

DEBUG_RWSEMS_WARN_ON((rwsem_owner(sem) != current) &&
!rwsem_test_oflags(sem, RWSEM_NONSPINNABLE)):

[syzbot]

Hello,

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

WARNING: CPU: 0 PID: 5970 at kernel/locking/rwsem.c:1381 __up_write kernel/locking/rwsem.c:1380 [inline]
WARNING: CPU: 0 PID: 5970 at kernel/locking/rwsem.c:1381 up_write+0x3a2/0x420 kernel/locking/rwsem.c:1643
Modules linked in:
CPU: 0 UID: 0 PID: 5970 Comm: syz.0.17 Not tainted syzkaller #0 PREEMPT(full)

Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.3-debian-1.16.3-2~bpo12+1 04/01/2014
RIP: 0010:__up_write kernel/locking/rwsem.c:1380 [inline]
RIP: 0010:up_write+0x3a2/0x420 kernel/locking/rwsem.c:1643

Code: d0 48 c7 c7 20 ff 6a 8b 48 c7 c6 40 01 6b 8b 48 8b 14 24 4c 89 f1 4d 89 e0 4c 8b 4c 24 08 41 52 e8 b3 36 e6 ff 48 83 c4 08 90 <0f> 0b 90 90 e9 6d fd ff ff 48 c7 c1 94 6e 9e 8f 80 e1 07 80 c1 03
RSP: 0018:ffffc9000d497c50 EFLAGS: 00010296
RAX: 29f4d5975a11a300 RBX: ffff888043da5058 RCX: ffff888034730000

RDX: 0000000000000000 RSI: 0000000000000001 RDI: 0000000000000002
RBP: dffffc0000000000 R08: 0000000000000003 R09: 0000000000000004
R10: dffffc0000000000 R11: fffffbfff1bfa650 R12: 0000000000000000

R13: ffff888043da50b0 R14: ffff888043da5058 R15: 1ffff110087b4a0c
FS: 00007f49f65fe6c0(0000) GS:ffff88808d300000(0000) knlGS:0000000000000000

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

CR2: 000000c005567000 CR3: 0000000058d8f000 CR4: 0000000000352ef0

Call Trace:
<TASK>
inode_unlock include/linux/fs.h:990 [inline]

chown_common+0x3fb/0x580 fs/open.c:794
do_fchownat+0x161/0x270 fs/open.c:823
__do_sys_lchown fs/open.c:848 [inline]
__se_sys_lchown fs/open.c:846 [inline]
__x64_sys_lchown+0x85/0xa0 fs/open.c:846

do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
do_syscall_64+0xfa/0xfa0 arch/x86/entry/syscall_64.c:94
entry_SYSCALL_64_after_hwframe+0x77/0x7f

RIP: 0033:0x7f49f6f8eec9

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:00007f49f65fe038 EFLAGS: 00000246 ORIG_RAX: 000000000000005e
RAX: ffffffffffffffda RBX: 00007f49f71e6270 RCX: 00007f49f6f8eec9

RDX: 000000000000ee01 RSI: 0000000000000000 RDI: 00002000000006c0

RBP: 00007f49f7011f91 R08: 0000000000000000 R09: 0000000000000000

R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000

R13: 00007f49f71e6308 R14: 00007f49f71e6270 R15: 00007fff9d14f498
</TASK>


Tested on:

commit: 98ac9cc4 Merge tag 'f2fs-fix-6.18-rc2' of git://git.ke..
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=171475e2580000

kernel config: https://syzkaller.appspot.com/x/.config?x=c2d7b4143707d3a0
dashboard link: https://syzkaller.appspot.com/bug?extid=04c2672c56fbb9401640
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=1448b67c580000