[syzbot] [gfs2?] KASAN: null-ptr-deref Write in gfs2_trans_add_revoke

[syzbot] [gfs2?] KASAN: null-ptr-deref Write in gfs2_trans_add_revoke

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit:    260f6f4fda93 Merge tag 'drm-next-2025-07-30' of https://gi..
git tree:       upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=1436e9bc580000
kernel config:  https://syzkaller.appspot.com/x/.config?x=3e6923811cbcd88f
dashboard link: https://syzkaller.appspot.com/bug?extid=f2b9fe431c853e793948
compiler:       Debian clang version 20.1.7 (++20250616065708+6146a88f6049-1~exp1~20250616065826.132), Debian LLD 20.1.7
syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=10a93ca2580000
C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=12089ca2580000

Downloadable assets:
disk image (non-bootable): https://storage.googleapis.com/syzbot-assets/d900f083ada3/non_bootable_disk-260f6f4f.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/28b1dc006a89/vmlinux-260f6f4f.xz
kernel image: https://storage.googleapis.com/syzbot-assets/dcbc50612705/bzImage-260f6f4f.xz
mounted in repro #1: https://storage.googleapis.com/syzbot-assets/f2243f65af89/mount_0.gz
  fsck result: OK (log: https://syzkaller.appspot.com/x/fsck.log?x=10089ca2580000)
mounted in repro #2: https://storage.googleapis.com/syzbot-assets/c6557c77eded/mount_8.gz
  fsck result: OK (log: https://syzkaller.appspot.com/x/fsck.log?x=169dc834580000)

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+f2b9fe431c853e793948@syzkaller.appspotmail.com

gfs2: fsid=syz:syz.0: first mount done, others may mount
==================================================================
BUG: KASAN: null-ptr-deref in instrument_atomic_write include/linux/instrumented.h:82 [inline]
BUG: KASAN: null-ptr-deref in set_bit include/asm-generic/bitops/instrumented-atomic.h:28 [inline]
BUG: KASAN: null-ptr-deref in gfs2_trans_add_revoke+0x8c/0xe0 fs/gfs2/trans.c:321
Write of size 8 at addr 0000000000000018 by task syz.0.17/5566

CPU: 0 UID: 0 PID: 5566 Comm: syz.0.17 Not tainted 6.16.0-syzkaller-08685-g260f6f4fda93 #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
Call Trace:
 <TASK>
 dump_stack_lvl+0x189/0x250 lib/dump_stack.c:120
 kasan_report+0x118/0x150 mm/kasan/report.c:595
 check_region_inline mm/kasan/generic.c:-1 [inline]
 kasan_check_range+0x2b0/0x2c0 mm/kasan/generic.c:189
 instrument_atomic_write include/linux/instrumented.h:82 [inline]
 set_bit include/asm-generic/bitops/instrumented-atomic.h:28 [inline]
 gfs2_trans_add_revoke+0x8c/0xe0 fs/gfs2/trans.c:321
 gfs2_remove_from_journal+0x43e/0x6d0 fs/gfs2/meta_io.c:366
 gfs2_discard fs/gfs2/aops.c:597 [inline]
 gfs2_invalidate_folio+0x579/0x750 fs/gfs2/aops.c:631
 folio_invalidate mm/truncate.c:140 [inline]
 truncate_cleanup_folio+0x2d5/0x430 mm/truncate.c:160
 truncate_inode_pages_range+0x233/0xda0 mm/truncate.c:379
 do_gfs2_set_flags fs/gfs2/file.c:254 [inline]
 gfs2_fileattr_set+0x80a/0x9b0 fs/gfs2/file.c:311
 vfs_fileattr_set+0x92f/0xb90 fs/file_attr.c:298
 ioctl_setflags+0x17b/0x200 fs/file_attr.c:336
 do_vfs_ioctl+0x8ed/0x1430 fs/ioctl.c:561
 __do_sys_ioctl fs/ioctl.c:596 [inline]
 __se_sys_ioctl+0x82/0x170 fs/ioctl.c:584
 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: 0033:0x7f55c3b8eb69
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:00007ffea6c68328 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
RAX: ffffffffffffffda RBX: 00007f55c3db5fa0 RCX: 00007f55c3b8eb69
RDX: 0000200000000000 RSI: 0000000040086602 RDI: 0000000000000005
RBP: 00007f55c3c11df1 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f55c3db5fa0 R14: 00007f55c3db5fa0 R15: 0000000000000003
 </TASK>
==================================================================


---
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Forwarded: Re: [syzbot] [gfs2?] KASAN: null-ptr-deref Write in gfs2_trans_add_revoke

[syzbot]

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

***

Subject: Re: [syzbot] [gfs2?] KASAN: null-ptr-deref Write in gfs2_trans_add_revoke
Author: lizhi.xu@windriver.com

#syz test

diff --git a/fs/gfs2/trans.c b/fs/gfs2/trans.c
index 075f7e9abe47..d1a34f928a18 100644
--- a/fs/gfs2/trans.c
+++ b/fs/gfs2/trans.c
@@ -314,7 +314,7 @@ void gfs2_trans_add_meta(struct gfs2_glock *gl, struct buffer_head *bh)
 
 void gfs2_trans_add_revoke(struct gfs2_sbd *sdp, struct gfs2_bufdata *bd)
 {
-	struct gfs2_trans *tr = current->journal_info;
+	struct gfs2_trans *tr = bd->bd_tr;
 
 	BUG_ON(!list_empty(&bd->bd_list));
 	gfs2_add_revoke(sdp, bd);

Re: [syzbot] [gfs2?] KASAN: null-ptr-deref Write in gfs2_trans_add_revoke

[syzbot]

Hello,

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

Reported-by: syzbot+f2b9fe431c853e793948@syzkaller.appspotmail.com
Tested-by: syzbot+f2b9fe431c853e793948@syzkaller.appspotmail.com

Tested on:

commit:         f2d282e1 Merge tag 'bitmap-for-6.17' of https://github..
git tree:       upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=171d82a2580000
kernel config:  https://syzkaller.appspot.com/x/.config?x=f288fd07ab21a0fb
dashboard link: https://syzkaller.appspot.com/bug?extid=f2b9fe431c853e793948
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=14b162a2580000

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

[PATCH] gfs2: Correct use of trans

[Lizhi Xu]

There are too many factors interfering with current->journal_info(for
example: dirty inode, write jdata batch, etc.). When trans begins, the
current->journal_info is set to a new value, but when trans ends, it is
set to NULL.

When revoking a trans, use the trans in bufdata directly.

Fixes: 75f2b879aeb3 ("GFS2: Merge revoke adding functions")
Reported-by: syzbot+f2b9fe431c853e793948@syzkaller.appspotmail.com
Closes: https://syzkaller.appspot.com/bug?extid=f2b9fe431c853e793948
Tested-by: syzbot+f2b9fe431c853e793948@syzkaller.appspotmail.com
Signed-off-by: Lizhi Xu <lizhi.xu@windriver.com>
---
 fs/gfs2/trans.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/fs/gfs2/trans.c b/fs/gfs2/trans.c
index 075f7e9abe47..d1a34f928a18 100644
--- a/fs/gfs2/trans.c
+++ b/fs/gfs2/trans.c
@@ -314,7 +314,7 @@ void gfs2_trans_add_meta(struct gfs2_glock *gl, struct buffer_head *bh)
 
 void gfs2_trans_add_revoke(struct gfs2_sbd *sdp, struct gfs2_bufdata *bd)
 {
-	struct gfs2_trans *tr = current->journal_info;
+	struct gfs2_trans *tr = bd->bd_tr;
 
 	BUG_ON(!list_empty(&bd->bd_list));
 	gfs2_add_revoke(sdp, bd);
-- 
2.43.0