[syzbot] [mm?] KASAN: use-after-free Read in copy_folio_from_iter_atomic (2)

[syzbot] [mm?] KASAN: use-after-free Read in copy_folio_from_iter_atomic (2)

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit:    24d479d26b25 Linux 6.19-rc6
git tree:       upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=15454e3a580000
kernel config:  https://syzkaller.appspot.com/x/.config?x=c33bf4a3a0c7a4f1
dashboard link: https://syzkaller.appspot.com/bug?extid=6cc93ec9a4035badb85f
compiler:       Debian clang version 21.1.8 (++20251221033036+2078da43e25a-1~exp1~20251221153213.50), Debian LLD 21.1.8

Unfortunately, I don't have any reproducer for this issue yet.

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/f0555f920605/disk-24d479d2.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/ae277d28fcd2/vmlinux-24d479d2.xz
kernel image: https://storage.googleapis.com/syzbot-assets/b4f8db4a51a6/bzImage-24d479d2.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+6cc93ec9a4035badb85f@syzkaller.appspotmail.com

==================================================================
BUG: KASAN: use-after-free in memcpy_from_iter lib/iov_iter.c:85 [inline]
BUG: KASAN: use-after-free in iterate_bvec include/linux/iov_iter.h:123 [inline]
BUG: KASAN: use-after-free in iterate_and_advance2 include/linux/iov_iter.h:306 [inline]
BUG: KASAN: use-after-free in iterate_and_advance include/linux/iov_iter.h:330 [inline]
BUG: KASAN: use-after-free in __copy_from_iter lib/iov_iter.c:261 [inline]
BUG: KASAN: use-after-free in copy_folio_from_iter_atomic+0xa6c/0x1950 lib/iov_iter.c:491
Read of size 4096 at addr ffff88803177d000 by task kworker/u8:9/1219

CPU: 0 UID: 0 PID: 1219 Comm: kworker/u8:9 Not tainted syzkaller #0 PREEMPT_{RT,(full)} 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/25/2025
Workqueue: loop1 loop_workfn
Call Trace:
 <TASK>
 dump_stack_lvl+0xe8/0x150 lib/dump_stack.c:120
 print_address_description mm/kasan/report.c:378 [inline]
 print_report+0xba/0x230 mm/kasan/report.c:482
 kasan_report+0x117/0x150 mm/kasan/report.c:595
 check_region_inline mm/kasan/generic.c:-1 [inline]
 kasan_check_range+0x264/0x2c0 mm/kasan/generic.c:200
 __asan_memcpy+0x29/0x70 mm/kasan/shadow.c:105
 memcpy_from_iter lib/iov_iter.c:85 [inline]
 iterate_bvec include/linux/iov_iter.h:123 [inline]
 iterate_and_advance2 include/linux/iov_iter.h:306 [inline]
 iterate_and_advance include/linux/iov_iter.h:330 [inline]
 __copy_from_iter lib/iov_iter.c:261 [inline]
 copy_folio_from_iter_atomic+0xa6c/0x1950 lib/iov_iter.c:491
 generic_perform_write+0x5b1/0x8b0 mm/filemap.c:4332
 shmem_file_write_iter+0xfb/0x120 mm/shmem.c:3490
 lo_rw_aio+0xc80/0xf00 include/linux/percpu-rwsem.h:-1
 do_req_filebacked drivers/block/loop.c:434 [inline]
 loop_handle_cmd drivers/block/loop.c:1947 [inline]
 loop_process_work+0x637/0x11b0 drivers/block/loop.c:1982
 process_one_work kernel/workqueue.c:3257 [inline]
 process_scheduled_works+0xaec/0x17a0 kernel/workqueue.c:3340
 worker_thread+0x89f/0xd90 kernel/workqueue.c:3421
 kthread+0x726/0x8b0 kernel/kthread.c:463
 ret_from_fork+0x51b/0xa40 arch/x86/kernel/process.c:158
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:246
 </TASK>

The buggy address belongs to the physical page:
page: refcount:0 mapcount:0 mapping:0000000000000000 index:0xffff88803177d000 pfn:0x3177d
flags: 0x80000000000000(node=0|zone=1)
raw: 0080000000000000 ffffea00016beb08 ffffea00009e42c8 0000000000000000
raw: ffff88803177d000 0000000000000000 00000000ffffffff 0000000000000000
page dumped because: kasan: bad access detected
page_owner tracks the page as freed
page last allocated via order 0, migratetype Unmovable, gfp_mask 0xdc0(GFP_KERNEL|__GFP_ZERO), pid 6876, tgid 6875 (syz.1.137), ts 163020649815, free_ts 163886382057
 set_page_owner include/linux/page_owner.h:32 [inline]
 post_alloc_hook+0x228/0x280 mm/page_alloc.c:1884
 prep_new_page mm/page_alloc.c:1892 [inline]
 get_page_from_freelist+0x28bb/0x2950 mm/page_alloc.c:3945
 __alloc_frozen_pages_noprof+0x18d/0x380 mm/page_alloc.c:5240
 alloc_pages_mpol+0xd1/0x380 mm/mempolicy.c:2486
 alloc_frozen_pages_noprof mm/mempolicy.c:2557 [inline]
 alloc_pages_noprof+0xce/0x1e0 mm/mempolicy.c:2577
 lbmLogInit fs/jfs/jfs_logmgr.c:1815 [inline]
 lmLogInit+0x357/0x1a00 fs/jfs/jfs_logmgr.c:1269
 open_inline_log fs/jfs/jfs_logmgr.c:1175 [inline]
 lmLogOpen+0x4e1/0xfa0 fs/jfs/jfs_logmgr.c:1069
 jfs_mount_rw+0xee/0x670 fs/jfs/jfs_mount.c:257
 jfs_fill_super+0x754/0xd80 fs/jfs/super.c:532
 get_tree_bdev_flags+0x431/0x4f0 fs/super.c:1691
 vfs_get_tree+0x92/0x2a0 fs/super.c:1751
 fc_mount fs/namespace.c:1199 [inline]
 do_new_mount_fc fs/namespace.c:3636 [inline]
 do_new_mount+0x329/0xa50 fs/namespace.c:3712
 do_mount fs/namespace.c:4035 [inline]
 __do_sys_mount fs/namespace.c:4224 [inline]
 __se_sys_mount+0x31d/0x420 fs/namespace.c:4201
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0xe2/0xf80 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
page last free pid 5804 tgid 5804 stack trace:
 reset_page_owner include/linux/page_owner.h:25 [inline]
 free_pages_prepare mm/page_alloc.c:1433 [inline]
 __free_frozen_pages+0xfc1/0x1130 mm/page_alloc.c:2973
 lbmLogShutdown fs/jfs/jfs_logmgr.c:1863 [inline]
 lmLogShutdown+0x44e/0x850 fs/jfs/jfs_logmgr.c:1683
 lmLogClose+0x28a/0x520 fs/jfs/jfs_logmgr.c:1459
 jfs_umount+0x2ef/0x3c0 fs/jfs/jfs_umount.c:114
 jfs_put_super+0x8c/0x190 fs/jfs/super.c:194
 generic_shutdown_super+0x135/0x2c0 fs/super.c:643
 kill_block_super+0x44/0x90 fs/super.c:1722
 deactivate_locked_super+0xbc/0x130 fs/super.c:474
 cleanup_mnt+0x437/0x4d0 fs/namespace.c:1318
 task_work_run+0x1d9/0x270 kernel/task_work.c:233
 resume_user_mode_work include/linux/resume_user_mode.h:50 [inline]
 __exit_to_user_mode_loop kernel/entry/common.c:44 [inline]
 exit_to_user_mode_loop+0xed/0x480 kernel/entry/common.c:75
 __exit_to_user_mode_prepare include/linux/irq-entry-common.h:226 [inline]
 syscall_exit_to_user_mode_prepare include/linux/irq-entry-common.h:256 [inline]
 syscall_exit_to_user_mode_work include/linux/entry-common.h:159 [inline]
 syscall_exit_to_user_mode include/linux/entry-common.h:194 [inline]
 do_syscall_64+0x2b7/0xf80 arch/x86/entry/syscall_64.c:100
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

Memory state around the buggy address:
 ffff88803177cf00: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
 ffff88803177cf80: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
>ffff88803177d000: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
                   ^
 ffff88803177d080: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
 ffff88803177d100: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
==================================================================


---
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Re: [syzbot] [mm?] KASAN: use-after-free Read in copy_folio_from_iter_atomic (2)

[syzbot]

syzbot has found a reproducer for the following issue on:

HEAD commit:    e6efabc0afca Add linux-next specific files for 20260414
git tree:       linux-next
console output: https://syzkaller.appspot.com/x/log.txt?x=17908702580000
kernel config:  https://syzkaller.appspot.com/x/.config?x=56c2b36de3316f1b
dashboard link: https://syzkaller.appspot.com/bug?extid=6cc93ec9a4035badb85f
compiler:       Debian clang version 21.1.8 (++20251221033036+2078da43e25a-1~exp1~20251221153213.50), Debian LLD 21.1.8
syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=14c798ce580000
C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=1142c4ce580000

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/e7099cbf73e4/disk-e6efabc0.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/439c402df1b9/vmlinux-e6efabc0.xz
kernel image: https://storage.googleapis.com/syzbot-assets/fc0c0175fc76/bzImage-e6efabc0.xz
mounted in repro: https://storage.googleapis.com/syzbot-assets/94fa7bad6be9/mount_0.gz
  fsck result: failed (log: https://syzkaller.appspot.com/x/fsck.log?x=17017b16580000)

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+6cc93ec9a4035badb85f@syzkaller.appspotmail.com

==================================================================
BUG: KASAN: use-after-free in memcpy_from_iter lib/iov_iter.c:85 [inline]
BUG: KASAN: use-after-free in iterate_bvec include/linux/iov_iter.h:123 [inline]
BUG: KASAN: use-after-free in iterate_and_advance2 include/linux/iov_iter.h:306 [inline]
BUG: KASAN: use-after-free in iterate_and_advance include/linux/iov_iter.h:330 [inline]
BUG: KASAN: use-after-free in __copy_from_iter lib/iov_iter.c:261 [inline]
BUG: KASAN: use-after-free in copy_folio_from_iter_atomic+0xbb5/0x1ad0 lib/iov_iter.c:491
Read of size 4096 at addr ffff888037cb3000 by task kworker/u8:7/1020

CPU: 0 UID: 0 PID: 1020 Comm: kworker/u8:7 Not tainted syzkaller #0 PREEMPT_{RT,(full)} 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 03/18/2026
Workqueue: loop0 loop_workfn
Call Trace:
 <TASK>
 dump_stack_lvl+0xe8/0x150 lib/dump_stack.c:120
 print_address_description+0x55/0x1e0 mm/kasan/report.c:378
 print_report+0x58/0x70 mm/kasan/report.c:482
 kasan_report+0x117/0x150 mm/kasan/report.c:595
 check_region_inline mm/kasan/generic.c:-1 [inline]
 kasan_check_range+0x264/0x2c0 mm/kasan/generic.c:200
 __asan_memcpy+0x29/0x70 mm/kasan/shadow.c:105
 memcpy_from_iter lib/iov_iter.c:85 [inline]
 iterate_bvec include/linux/iov_iter.h:123 [inline]
 iterate_and_advance2 include/linux/iov_iter.h:306 [inline]
 iterate_and_advance include/linux/iov_iter.h:330 [inline]
 __copy_from_iter lib/iov_iter.c:261 [inline]
 copy_folio_from_iter_atomic+0xbb5/0x1ad0 lib/iov_iter.c:491
 generic_perform_write+0x5b1/0x8b0 mm/filemap.c:4342
 shmem_file_write_iter+0xfb/0x120 mm/shmem.c:3478
 lo_rw_aio+0xc80/0xf00 include/linux/percpu-rwsem.h:-1
 do_req_filebacked drivers/block/loop.c:433 [inline]
 loop_handle_cmd drivers/block/loop.c:1925 [inline]
 loop_process_work+0x637/0x11b0 drivers/block/loop.c:1960
 process_one_work kernel/workqueue.c:3308 [inline]
 process_scheduled_works+0xb68/0x1910 kernel/workqueue.c:3399
 worker_thread+0xa90/0x1040 kernel/workqueue.c:3485
 kthread+0x388/0x470 kernel/kthread.c:436
 ret_from_fork+0x514/0xb70 arch/x86/kernel/process.c:158
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245
 </TASK>

The buggy address belongs to the physical page:
page: refcount:0 mapcount:0 mapping:0000000000000000 index:0x38 pfn:0x37cb3
flags: 0x80000000000000(node=0|zone=1)
raw: 0080000000000000 ffffea0000d17548 ffffea0001353448 0000000000000000
raw: 0000000000000038 0000000000000000 00000000ffffffff 0000000000000000
page dumped because: kasan: bad access detected
page_owner tracks the page as freed
page last allocated via order 0, migratetype Unmovable, gfp_mask 0xdc0(GFP_KERNEL|__GFP_ZERO), pid 6098, tgid 6098 (syz.0.91), ts 154383709391, free_ts 154428922615
 set_page_owner include/linux/page_owner.h:32 [inline]
 post_alloc_hook+0x231/0x280 mm/page_alloc.c:1858
 prep_new_page mm/page_alloc.c:1866 [inline]
 get_page_from_freelist+0x27d6/0x2850 mm/page_alloc.c:3946
 __alloc_frozen_pages_noprof+0x18d/0x380 mm/page_alloc.c:5226
 alloc_pages_mpol+0xd1/0x380 mm/mempolicy.c:2490
 alloc_frozen_pages_noprof mm/mempolicy.c:2561 [inline]
 alloc_pages_noprof+0xd2/0x2f0 mm/mempolicy.c:2581
 lbmLogInit fs/jfs/jfs_logmgr.c:1813 [inline]
 lmLogInit+0x357/0x1a00 fs/jfs/jfs_logmgr.c:1267
 open_inline_log fs/jfs/jfs_logmgr.c:1173 [inline]
 lmLogOpen+0x4e1/0xfa0 fs/jfs/jfs_logmgr.c:1067
 jfs_mount_rw+0xee/0x670 fs/jfs/jfs_mount.c:257
 jfs_fill_super+0x754/0xd80 fs/jfs/super.c:532
 get_tree_bdev_flags+0x431/0x4f0 fs/super.c:1694
 vfs_get_tree+0x92/0x2a0 fs/super.c:1754
 fc_mount fs/namespace.c:1193 [inline]
 do_new_mount_fc fs/namespace.c:3758 [inline]
 do_new_mount+0x341/0xd30 fs/namespace.c:3834
 do_mount fs/namespace.c:4167 [inline]
 __do_sys_mount fs/namespace.c:4399 [inline]
 __se_sys_mount+0x31d/0x420 fs/namespace.c:4376
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0x15f/0xf80 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
page last free pid 5945 tgid 5945 stack trace:
 reset_page_owner include/linux/page_owner.h:25 [inline]
 __free_pages_prepare mm/page_alloc.c:1402 [inline]
 __free_frozen_pages+0xf9b/0x10f0 mm/page_alloc.c:2943
 lbmLogShutdown fs/jfs/jfs_logmgr.c:1861 [inline]
 lmLogShutdown+0x44e/0x850 fs/jfs/jfs_logmgr.c:1681
 lmLogClose+0x28a/0x520 fs/jfs/jfs_logmgr.c:1457
 jfs_umount+0x2fb/0x3d0 fs/jfs/jfs_umount.c:124
 jfs_put_super+0x8c/0x190 fs/jfs/super.c:194
 generic_shutdown_super+0x13d/0x2d0 fs/super.c:646
 kill_block_super+0x44/0x90 fs/super.c:1725
 deactivate_locked_super+0xbc/0x130 fs/super.c:476
 cleanup_mnt+0x437/0x4d0 fs/namespace.c:1312
 task_work_run+0x1d9/0x270 kernel/task_work.c:233
 resume_user_mode_work include/linux/resume_user_mode.h:50 [inline]
 __exit_to_user_mode_loop kernel/entry/common.c:67 [inline]
 exit_to_user_mode_loop+0xed/0x480 kernel/entry/common.c:98
 __exit_to_user_mode_prepare include/linux/irq-entry-common.h:207 [inline]
 syscall_exit_to_user_mode_prepare include/linux/irq-entry-common.h:238 [inline]
 syscall_exit_to_user_mode include/linux/entry-common.h:328 [inline]
 do_syscall_64+0x33e/0xf80 arch/x86/entry/syscall_64.c:100
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

Memory state around the buggy address:
 ffff888037cb2f00: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
 ffff888037cb2f80: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
>ffff888037cb3000: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
                   ^
 ffff888037cb3080: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
 ffff888037cb3100: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
==================================================================


---
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.

Forwarded: Re: [syzbot] [mm?] KASAN: use-after-free Read in copy_folio_from_iter_atomic (2)

[syzbot]

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

***

Subject: Re: [syzbot] [mm?] KASAN: use-after-free Read in copy_folio_from_iter_atomic (2)
Author: suresh.k.chandrappa@gmail.com

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

diff --git a/fs/jfs/jfs_logmgr.c b/fs/jfs/jfs_logmgr.c
index 306165e61438..e8ae90be089b 100644
--- a/fs/jfs/jfs_logmgr.c
+++ b/fs/jfs/jfs_logmgr.c
@@ -1804,6 +1804,7 @@ static int lbmLogInit(struct jfs_log * log)
     * avoid deadlock here.
     */
    init_waitqueue_head(&log->free_wait);
+   init_waitqueue_head(&log->io_waitq);

    log->lbuf_free = NULL;

@@ -1855,6 +1856,8 @@ static void lbmLogShutdown(struct jfs_log * log)

    jfs_info("lbmLogShutdown: log:0x%p", log);

+   wait_event(log->io_waitq, !atomic_read(&log->io_inflight));
+
    lbuf = log->lbuf_free;
    while (lbuf) {
        struct lbuf *next = lbuf->l_freelist;
@@ -1976,6 +1979,8 @@ static int lbmRead(struct jfs_log * log, int pn,
struct lbuf ** bpp)

    bio->bi_end_io = lbmIODone;
    bio->bi_private = bp;
+
+   atomic_inc(&log->io_inflight);
    /*check if journaling to disk has been disabled*/
    if (log->no_integrity) {
        bio->bi_iter.bi_size = 0;
@@ -2123,6 +2128,7 @@ static void lbmStartIO(struct lbuf * bp)
    bio->bi_end_io = lbmIODone;
    bio->bi_private = bp;

+   atomic_inc(&log->io_inflight);
    /* check if journaling to disk has been disabled */
    if (log->no_integrity) {
        bio->bi_iter.bi_size = 0;
@@ -2186,6 +2192,8 @@ static void lbmIODone(struct bio *bio)

    bio_put(bio);

+   log = bp->l_log;
+
    /*
     *  pagein completion
     */
@@ -2214,7 +2222,6 @@ static void lbmIODone(struct bio *bio)
    INCREMENT(lmStat.pagedone);

    /* update committed lsn */
-   log = bp->l_log;
    log->clsn = (bp->l_pn << L2LOGPSIZE) + bp->l_ceor;

    if (bp->l_flag & lbmDIRECT) {
@@ -2299,6 +2306,9 @@ static void lbmIODone(struct bio *bio)
 out:
    bp->l_flag |= lbmDONE;
    LCACHE_UNLOCK(flags);
+
+   if (atomic_dec_and_test(&log->io_inflight))
+       wake_up(&log->io_waitq);
 }

 int jfsIOWait(void *arg)
diff --git a/fs/jfs/jfs_logmgr.h b/fs/jfs/jfs_logmgr.h
index 09e0ef6aecce..d8858448de6f 100644
--- a/fs/jfs/jfs_logmgr.h
+++ b/fs/jfs/jfs_logmgr.h
@@ -400,6 +400,9 @@ struct jfs_log {
    uuid_t uuid;        /* 16: 128-bit uuid of log device */

    int no_integrity;   /* 3: flag to disable journaling to disk */
+
+   atomic_t io_inflight;
+   wait_queue_head_t io_waitq;
 };

 /*
--
2.43.0

Forwarded: Re: [syzbot] [mm?] KASAN: use-after-free Read in copy_folio_from_iter_atomic (2)

[syzbot]

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

***

Subject: Re: [syzbot] [mm?] KASAN: use-after-free Read in copy_folio_from_iter_atomic (2)
Author: suresh.k.chandrappa@gmail.com

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

From 56a838ee6e3c6834a7e7705472144b1c84a4d8f8 Mon Sep 17 00:00:00 2001
From: Suresh K C <suresh.k.chandrappa@gmail.com>
Date: Sat, 18 Apr 2026 10:14:20 +0530
Subject: [PATCH] jfs: fix use-after-free in lbmIODone

Add an atomic io_inflight counter and a wait queue (io_waitq) to
struct jfs_log to track in-flight I/O operations. This ensures that
lbmLogShutdown() waits for all pending log I/O to complete before
freeing log buffers, preventing a use-after-free race condition where
the loop device workqueue could still be reading from log buffer pages
that have already been freed.

The io_inflight counter is incremented in lbmRead() and lbmStartIO()
before submitting bios, and decremented in lbmIODone() after I/O
completion processing is finished.

Reported-by: syzbot+6cc93ec9a4035badb85f@syzkaller.appspotmail.com
Signed-off-by: Suresh K C <suresh.k.chandrappa@gmail.com>
---
 fs/jfs/jfs_logmgr.c | 12 +++++++++++-
 fs/jfs/jfs_logmgr.h |  3 +++
 2 files changed, 14 insertions(+), 1 deletion(-)

diff --git a/fs/jfs/jfs_logmgr.c b/fs/jfs/jfs_logmgr.c
index 306165e61438..e8ae90be089b 100644
--- a/fs/jfs/jfs_logmgr.c
+++ b/fs/jfs/jfs_logmgr.c
@@ -1804,6 +1804,7 @@ static int lbmLogInit(struct jfs_log * log)
      * avoid deadlock here.
      */
     init_waitqueue_head(&log->free_wait);
+    init_waitqueue_head(&log->io_waitq);

     log->lbuf_free = NULL;

@@ -1855,6 +1856,8 @@ static void lbmLogShutdown(struct jfs_log * log)

     jfs_info("lbmLogShutdown: log:0x%p", log);

+    wait_event(log->io_waitq, !atomic_read(&log->io_inflight));
+
     lbuf = log->lbuf_free;
     while (lbuf) {
         struct lbuf *next = lbuf->l_freelist;
@@ -1976,6 +1979,8 @@ static int lbmRead(struct jfs_log * log, int pn,
struct lbuf ** bpp)

     bio->bi_end_io = lbmIODone;
     bio->bi_private = bp;
+
+    atomic_inc(&log->io_inflight);
     /*check if journaling to disk has been disabled*/
     if (log->no_integrity) {
         bio->bi_iter.bi_size = 0;
@@ -2123,6 +2128,7 @@ static void lbmStartIO(struct lbuf * bp)
     bio->bi_end_io = lbmIODone;
     bio->bi_private = bp;

+    atomic_inc(&log->io_inflight);
     /* check if journaling to disk has been disabled */
     if (log->no_integrity) {
         bio->bi_iter.bi_size = 0;
@@ -2186,6 +2192,8 @@ static void lbmIODone(struct bio *bio)

     bio_put(bio);

+    log = bp->l_log;
+
     /*
      *    pagein completion
      */
@@ -2214,7 +2222,6 @@ static void lbmIODone(struct bio *bio)
     INCREMENT(lmStat.pagedone);

     /* update committed lsn */
-    log = bp->l_log;
     log->clsn = (bp->l_pn << L2LOGPSIZE) + bp->l_ceor;

     if (bp->l_flag & lbmDIRECT) {
@@ -2299,6 +2306,9 @@ static void lbmIODone(struct bio *bio)
 out:
     bp->l_flag |= lbmDONE;
     LCACHE_UNLOCK(flags);
+
+    if (atomic_dec_and_test(&log->io_inflight))
+        wake_up(&log->io_waitq);
 }

 int jfsIOWait(void *arg)
diff --git a/fs/jfs/jfs_logmgr.h b/fs/jfs/jfs_logmgr.h
index 09e0ef6aecce..d8858448de6f 100644
--- a/fs/jfs/jfs_logmgr.h
+++ b/fs/jfs/jfs_logmgr.h
@@ -400,6 +400,9 @@ struct jfs_log {
     uuid_t uuid;        /* 16: 128-bit uuid of log device */

     int no_integrity;    /* 3: flag to disable journaling to disk */
+
+    atomic_t io_inflight;
+    wait_queue_head_t io_waitq;
 };

 /*
-- 
2.43.0

Forwarded: Re: [syzbot] [mm?] KASAN: use-after-free Read in copy_folio_from_iter_atomic (2)

[syzbot]

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

***

Subject: Re: [syzbot] [mm?] KASAN: use-after-free Read in copy_folio_from_iter_atomic (2)
Author: suresh.k.chandrappa@gmail.com

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

diff --git a/fs/jfs/jfs_logmgr.c b/fs/jfs/jfs_logmgr.c
index 306165e61438..e8ae90be089b 100644
--- a/fs/jfs/jfs_logmgr.c
+++ b/fs/jfs/jfs_logmgr.c
@@ -1804,6 +1804,7 @@ static int lbmLogInit(struct jfs_log * log)
      * avoid deadlock here.
      */
     init_waitqueue_head(&log->free_wait);
+    init_waitqueue_head(&log->io_waitq);

     log->lbuf_free = NULL;

@@ -1855,6 +1856,8 @@ static void lbmLogShutdown(struct jfs_log * log)

     jfs_info("lbmLogShutdown: log:0x%p", log);

+    wait_event(log->io_waitq, !atomic_read(&log->io_inflight));
+
     lbuf = log->lbuf_free;
     while (lbuf) {
         struct lbuf *next = lbuf->l_freelist;
@@ -1976,6 +1979,8 @@ static int lbmRead(struct jfs_log * log, int pn,
struct lbuf ** bpp)

     bio->bi_end_io = lbmIODone;
     bio->bi_private = bp;
+
+    atomic_inc(&log->io_inflight);
     /*check if journaling to disk has been disabled*/
     if (log->no_integrity) {
         bio->bi_iter.bi_size = 0;
@@ -2123,6 +2128,7 @@ static void lbmStartIO(struct lbuf * bp)
     bio->bi_end_io = lbmIODone;
     bio->bi_private = bp;

+    atomic_inc(&log->io_inflight);
     /* check if journaling to disk has been disabled */
     if (log->no_integrity) {
         bio->bi_iter.bi_size = 0;
@@ -2186,6 +2192,8 @@ static void lbmIODone(struct bio *bio)

     bio_put(bio);

+    log = bp->l_log;
+
     /*
      *    pagein completion
      */
@@ -2214,7 +2222,6 @@ static void lbmIODone(struct bio *bio)
     INCREMENT(lmStat.pagedone);

     /* update committed lsn */
-    log = bp->l_log;
     log->clsn = (bp->l_pn << L2LOGPSIZE) + bp->l_ceor;

     if (bp->l_flag & lbmDIRECT) {
@@ -2299,6 +2306,9 @@ static void lbmIODone(struct bio *bio)
 out:
     bp->l_flag |= lbmDONE;
     LCACHE_UNLOCK(flags);
+
+    if (atomic_dec_and_test(&log->io_inflight))
+        wake_up(&log->io_waitq);
 }

 int jfsIOWait(void *arg)
diff --git a/fs/jfs/jfs_logmgr.h b/fs/jfs/jfs_logmgr.h
index 09e0ef6aecce..d8858448de6f 100644
--- a/fs/jfs/jfs_logmgr.h
+++ b/fs/jfs/jfs_logmgr.h
@@ -400,6 +400,9 @@ struct jfs_log {
     uuid_t uuid;        /* 16: 128-bit uuid of log device */

     int no_integrity;    /* 3: flag to disable journaling to disk */
+
+    atomic_t io_inflight;
+    wait_queue_head_t io_waitq;
 };

Forwarded: [PATCH 1/1] jfs: try syzbot fix

[syzbot]

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

***

Subject: [PATCH 1/1] jfs: try syzbot fix
Author: jakovnovak30@gmail.com

#syz test

---
 fs/jfs/jfs_logmgr.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/fs/jfs/jfs_logmgr.c b/fs/jfs/jfs_logmgr.c
index 306165e61438..b319a4f542d8 100644
--- a/fs/jfs/jfs_logmgr.c
+++ b/fs/jfs/jfs_logmgr.c
@@ -1855,6 +1855,8 @@ static void lbmLogShutdown(struct jfs_log * log)
 
 	jfs_info("lbmLogShutdown: log:0x%p", log);
 
+	LOG_LOCK(log);
+
 	lbuf = log->lbuf_free;
 	while (lbuf) {
 		struct lbuf *next = lbuf->l_freelist;
@@ -1862,6 +1864,8 @@ static void lbmLogShutdown(struct jfs_log * log)
 		kfree(lbuf);
 		lbuf = next;
 	}
+
+	LOG_UNLOCK(log);
 }
 
 
-- 
2.53.0

Forwarded: Re: [syzbot] [mm?] KASAN: use-after-free Read in copy_folio_from_iter_atomic (2)

[syzbot]

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

***

Subject: Re: [syzbot] [mm?] KASAN: use-after-free Read in copy_folio_from_iter_atomic (2)
Author: mashiro.chen@mailbox.org

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

From 14bc67ec17b9a209d97c08e9136eead0bd0c0914 Mon Sep 17 00:00:00 2001
From: Mashiro Chen <mashiro.chen@mailbox.org>
Date: Sat, 25 Apr 2026 01:56:00 +0800
Subject: [PATCH] jfs: fix use-after-free on log shutdown

During JFS log shutdown, log buffer pages can be freed while lower-layer
loop workers are still copying from them, triggering a use-after-free
reported by syzbot in copy_folio_from_iter_atomic().

Track in-flight log I/O in struct jfs_log and wait for completion before
freeing log buffers. Add io_inflight/io_waitq, increment io_inflight
before submitting BIOs in lbmRead() and lbmStartIO(), and decrement it
from lbmIODone() on all completion paths, including READ and DIRECT
early-return paths.

This closes the teardown race between buffer page free and late I/O
completion.

Reported-by: syzbot+6cc93ec9a4035badb85f@syzkaller.appspotmail.com
Closes: https://syzkaller.appspot.com/bug?extid=6cc93ec9a4035badb85f
Signed-off-by: Mashiro Chen <mashiro.chen@mailbox.org>
---
 fs/jfs/jfs_logmgr.c | 17 +++++++++++++++--
 fs/jfs/jfs_logmgr.h |  2 ++
 2 files changed, 17 insertions(+), 2 deletions(-)

diff --git a/fs/jfs/jfs_logmgr.c b/fs/jfs/jfs_logmgr.c
index ada00d5bc214..a45c8e2559e4 100644
--- a/fs/jfs/jfs_logmgr.c
+++ b/fs/jfs/jfs_logmgr.c
@@ -1806,6 +1806,8 @@ static int lbmLogInit(struct jfs_log * log)
 	 * avoid deadlock here.
 	 */
 	init_waitqueue_head(&log->free_wait);
+	init_waitqueue_head(&log->io_waitq);
+	atomic_set(&log->io_inflight, 0);
 
 	log->lbuf_free = NULL;
 
@@ -1857,6 +1859,8 @@ static void lbmLogShutdown(struct jfs_log * log)
 
 	jfs_info("lbmLogShutdown: log:0x%p", log);
 
+	wait_event(log->io_waitq, !atomic_read(&log->io_inflight));
+
 	lbuf = log->lbuf_free;
 	while (lbuf) {
 		struct lbuf *next = lbuf->l_freelist;
@@ -1978,6 +1982,7 @@ static int lbmRead(struct jfs_log * log, int pn, struct lbuf ** bpp)
 
 	bio->bi_end_io = lbmIODone;
 	bio->bi_private = bp;
+	atomic_inc(&log->io_inflight);
 	/*check if journaling to disk has been disabled*/
 	if (log->no_integrity) {
 		bio->bi_iter.bi_size = 0;
@@ -2124,6 +2129,7 @@ static void lbmStartIO(struct lbuf * bp)
 
 	bio->bi_end_io = lbmIODone;
 	bio->bi_private = bp;
+	atomic_inc(&log->io_inflight);
 
 	/* check if journaling to disk has been disabled */
 	if (log->no_integrity) {
@@ -2170,7 +2176,7 @@ static void lbmIODone(struct bio *bio)
 {
 	struct lbuf *bp = bio->bi_private;
 	struct lbuf *nextbp, *tail;
-	struct jfs_log *log;
+	struct jfs_log *log = bp->l_log;
 	unsigned long flags;
 
 	/*
@@ -2201,6 +2207,9 @@ static void lbmIODone(struct bio *bio)
 		/* wakeup I/O initiator */
 		LCACHE_WAKEUP(&bp->l_ioevent);
 
+		if (atomic_dec_and_test(&log->io_inflight))
+			wake_up(&log->io_waitq);
+
 		return;
 	}
 
@@ -2220,12 +2229,13 @@ static void lbmIODone(struct bio *bio)
 	INCREMENT(lmStat.pagedone);
 
 	/* update committed lsn */
-	log = bp->l_log;
 	log->clsn = (bp->l_pn << L2LOGPSIZE) + bp->l_ceor;
 
 	if (bp->l_flag & lbmDIRECT) {
 		LCACHE_WAKEUP(&bp->l_ioevent);
 		LCACHE_UNLOCK(flags);
+		if (atomic_dec_and_test(&log->io_inflight))
+			wake_up(&log->io_waitq);
 		return;
 	}
 
@@ -2305,6 +2315,9 @@ static void lbmIODone(struct bio *bio)
 
 		LCACHE_UNLOCK(flags);	/* unlock+enable */
 	}
+
+	if (atomic_dec_and_test(&log->io_inflight))
+		wake_up(&log->io_waitq);
 }
 
 int jfsIOWait(void *arg)
diff --git a/fs/jfs/jfs_logmgr.h b/fs/jfs/jfs_logmgr.h
index 8b8994e48cd0..59cb0aca99c5 100644
--- a/fs/jfs/jfs_logmgr.h
+++ b/fs/jfs/jfs_logmgr.h
@@ -400,6 +400,8 @@ struct jfs_log {
 	uuid_t uuid;		/* 16: 128-bit uuid of log device */
 
 	int no_integrity;	/* 3: flag to disable journaling to disk */
+	atomic_t io_inflight;
+	wait_queue_head_t io_waitq;
 };
 
 /*
-- 
2.54.0

Forwarded: [PATCH] jfs: fix use-after-free on log shutdown

[syzbot]

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

***

Subject: [PATCH] jfs: fix use-after-free on log shutdown
Author: mashiro.chen@mailbox.org

During JFS log shutdown, log buffer pages can be freed while lower-layer
loop workers are still copying from them, triggering a use-after-free
reported by syzbot in copy_folio_from_iter_atomic().

Track in-flight log I/O in struct jfs_log and wait for completion before
freeing log buffers. Add io_inflight/io_waitq, increment io_inflight
before submitting BIOs in lbmRead() and lbmStartIO(), and decrement it
in lbmIODone() at the unified out: label, which all completion paths
including READ, DIRECT, synchronous, GC, asynchronous converge on.

This closes the teardown race between buffer page free and late I/O
completion.

Reported-by: syzbot+6cc93ec9a4035badb85f@syzkaller.appspotmail.com
Closes: https://syzkaller.appspot.com/bug?extid=6cc93ec9a4035badb85f
Signed-off-by: Mashiro Chen <mashiro.chen@mailbox.org>
---
#syz test: git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git master

 fs/jfs/jfs_logmgr.c | 11 +++++++++--
 fs/jfs/jfs_logmgr.h |  2 ++
 2 files changed, 11 insertions(+), 2 deletions(-)

diff --git a/fs/jfs/jfs_logmgr.c b/fs/jfs/jfs_logmgr.c
index 306165e61438..a567dae3b908 100644
--- a/fs/jfs/jfs_logmgr.c
+++ b/fs/jfs/jfs_logmgr.c
@@ -1804,6 +1804,8 @@ static int lbmLogInit(struct jfs_log * log)
 	 * avoid deadlock here.
 	 */
 	init_waitqueue_head(&log->free_wait);
+	init_waitqueue_head(&log->io_waitq);
+	atomic_set(&log->io_inflight, 0);
 
 	log->lbuf_free = NULL;
 
@@ -1855,6 +1857,8 @@ static void lbmLogShutdown(struct jfs_log * log)
 
 	jfs_info("lbmLogShutdown: log:0x%p", log);
 
+	wait_event(log->io_waitq, !atomic_read(&log->io_inflight));
+
 	lbuf = log->lbuf_free;
 	while (lbuf) {
 		struct lbuf *next = lbuf->l_freelist;
@@ -1976,6 +1980,7 @@ static int lbmRead(struct jfs_log * log, int pn, struct lbuf ** bpp)
 
 	bio->bi_end_io = lbmIODone;
 	bio->bi_private = bp;
+	atomic_inc(&log->io_inflight);
 	/*check if journaling to disk has been disabled*/
 	if (log->no_integrity) {
 		bio->bi_iter.bi_size = 0;
@@ -2122,6 +2127,7 @@ static void lbmStartIO(struct lbuf * bp)
 
 	bio->bi_end_io = lbmIODone;
 	bio->bi_private = bp;
+	atomic_inc(&log->io_inflight);
 
 	/* check if journaling to disk has been disabled */
 	if (log->no_integrity) {
@@ -2168,7 +2174,7 @@ static void lbmIODone(struct bio *bio)
 {
 	struct lbuf *bp = bio->bi_private;
 	struct lbuf *nextbp, *tail;
-	struct jfs_log *log;
+	struct jfs_log *log = bp->l_log;
 	unsigned long flags;
 
 	/*
@@ -2214,7 +2220,6 @@ static void lbmIODone(struct bio *bio)
 	INCREMENT(lmStat.pagedone);
 
 	/* update committed lsn */
-	log = bp->l_log;
 	log->clsn = (bp->l_pn << L2LOGPSIZE) + bp->l_ceor;
 
 	if (bp->l_flag & lbmDIRECT) {
@@ -2299,6 +2304,8 @@ static void lbmIODone(struct bio *bio)
 out:
 	bp->l_flag |= lbmDONE;
 	LCACHE_UNLOCK(flags);
+	if (atomic_dec_and_test(&log->io_inflight))
+		wake_up(&log->io_waitq);
 }
 
 int jfsIOWait(void *arg)
diff --git a/fs/jfs/jfs_logmgr.h b/fs/jfs/jfs_logmgr.h
index 09e0ef6aecce..31b826d546c0 100644
--- a/fs/jfs/jfs_logmgr.h
+++ b/fs/jfs/jfs_logmgr.h
@@ -400,6 +400,8 @@ struct jfs_log {
 	uuid_t uuid;		/* 16: 128-bit uuid of log device */
 
 	int no_integrity;	/* 3: flag to disable journaling to disk */
+	atomic_t io_inflight;
+	wait_queue_head_t io_waitq;
 };
 
 /*
-- 
2.54.0