[syzbot] KASAN: use-after-free Read in copy_page_from_iter_atomic

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: 7d2a07b76933 Linux 5.14
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=12fe8af5300000
kernel config: https://syzkaller.appspot.com/x/.config?x=113c5df900d8cf12
dashboard link: https://syzkaller.appspot.com/bug?extid=ffc4eceb22dfcf9fd6a0
compiler: Debian clang version 11.0.1-2, GNU ld (GNU Binutils for Debian) 2.35.1

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

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+ffc4ec...@syzkaller.appspotmail.com

==================================================================
BUG: KASAN: use-after-free in copy_page_from_iter_atomic+0x9c7/0x1520 lib/iov_iter.c:918
Read of size 4096 at addr ffff8880298b0000 by task kworker/u4:8/11701

CPU: 0 PID: 11701 Comm: kworker/u4:8 Not tainted 5.14.0-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
Workqueue: loop5 loop_rootcg_workfn
Call Trace:
__dump_stack lib/dump_stack.c:88 [inline]
dump_stack_lvl+0x1ae/0x29f lib/dump_stack.c:105
print_address_description+0x66/0x3b0 mm/kasan/report.c:233
__kasan_report mm/kasan/report.c:419 [inline]
kasan_report+0x163/0x210 mm/kasan/report.c:436
check_region_inline mm/kasan/generic.c:135 [inline]
kasan_check_range+0x2b5/0x2f0 mm/kasan/generic.c:189
memcpy+0x25/0x60 mm/kasan/shadow.c:65
copy_page_from_iter_atomic+0x9c7/0x1520 lib/iov_iter.c:918
generic_perform_write+0x2dd/0x580 mm/filemap.c:3664
__generic_file_write_iter+0x225/0x5a0 mm/filemap.c:3783
generic_file_write_iter+0xa7/0x1b0 mm/filemap.c:3815
do_iter_readv_writev+0x566/0x770 include/linux/fs.h:2108
do_iter_write+0x16c/0x5f0 fs/read_write.c:866
lo_write_bvec+0x267/0x6f0 drivers/block/loop.c:328
lo_write_simple drivers/block/loop.c:350 [inline]
do_req_filebacked drivers/block/loop.c:668 [inline]
loop_handle_cmd drivers/block/loop.c:2204 [inline]
loop_process_work+0x21c2/0x2cc0 drivers/block/loop.c:2244
process_one_work+0x833/0x10c0 kernel/workqueue.c:2276
worker_thread+0xac1/0x1320 kernel/workqueue.c:2422
kthread+0x453/0x480 kernel/kthread.c:319
ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:295

The buggy address belongs to the page:
page:ffffea0000a62c00 refcount:0 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x298b0
flags: 0xfff00000000000(node=0|zone=1|lastcpupid=0x7ff)
raw: 00fff00000000000 ffffea0000bb3348 ffffea0000d492c8 0000000000000000
raw: 0000000000000000 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 20552, ts 462739681694, free_ts 462770335978
prep_new_page mm/page_alloc.c:2436 [inline]
get_page_from_freelist+0x779/0xa30 mm/page_alloc.c:4168
__alloc_pages+0x26c/0x5f0 mm/page_alloc.c:5390
lbmLogInit fs/jfs/jfs_logmgr.c:1824 [inline]
lmLogInit+0x2fc/0x1e90 fs/jfs/jfs_logmgr.c:1278
open_inline_log fs/jfs/jfs_logmgr.c:1183 [inline]
lmLogOpen+0x505/0x1190 fs/jfs/jfs_logmgr.c:1077
jfs_mount_rw+0xe7/0x710 fs/jfs/jfs_mount.c:260
jfs_fill_super+0x64c/0xc20 fs/jfs/super.c:570
mount_bdev+0x26c/0x3a0 fs/super.c:1368
legacy_get_tree+0xea/0x180 fs/fs_context.c:610
vfs_get_tree+0x86/0x270 fs/super.c:1498
do_new_mount fs/namespace.c:2923 [inline]
path_mount+0x1981/0x2c10 fs/namespace.c:3253
do_mount fs/namespace.c:3266 [inline]
__do_sys_mount fs/namespace.c:3474 [inline]
__se_sys_mount+0x2f9/0x3b0 fs/namespace.c:3451
do_syscall_x64 arch/x86/entry/common.c:50 [inline]
do_syscall_64+0x3d/0xb0 arch/x86/entry/common.c:80
entry_SYSCALL_64_after_hwframe+0x44/0xae
page last free stack trace:
reset_page_owner include/linux/page_owner.h:24 [inline]
free_pages_prepare mm/page_alloc.c:1346 [inline]
free_pcp_prepare+0xc29/0xd20 mm/page_alloc.c:1397
free_unref_page_prepare mm/page_alloc.c:3332 [inline]
free_unref_page+0x7e/0x550 mm/page_alloc.c:3411
lbmLogShutdown fs/jfs/jfs_logmgr.c:1872 [inline]
lmLogShutdown+0x4ad/0x920 fs/jfs/jfs_logmgr.c:1692
lmLogClose+0x2c2/0x560 fs/jfs/jfs_logmgr.c:1468
jfs_umount+0x297/0x370 fs/jfs/jfs_umount.c:116
jfs_fill_super+0x8e5/0xc20 fs/jfs/super.c:605
mount_bdev+0x26c/0x3a0 fs/super.c:1368
legacy_get_tree+0xea/0x180 fs/fs_context.c:610
vfs_get_tree+0x86/0x270 fs/super.c:1498
do_new_mount fs/namespace.c:2923 [inline]
path_mount+0x1981/0x2c10 fs/namespace.c:3253
do_mount fs/namespace.c:3266 [inline]
__do_sys_mount fs/namespace.c:3474 [inline]
__se_sys_mount+0x2f9/0x3b0 fs/namespace.c:3451
do_syscall_x64 arch/x86/entry/common.c:50 [inline]
do_syscall_64+0x3d/0xb0 arch/x86/entry/common.c:80
entry_SYSCALL_64_after_hwframe+0x44/0xae

Memory state around the buggy address:
ffff8880298aff00: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
ffff8880298aff80: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
>ffff8880298b0000: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
^
ffff8880298b0080: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
ffff8880298b0100: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
==================================================================


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[Dave Kleikamp]

On 9/19/21 18:19, Andrew Morton wrote:
> might be a loop-vs-jfs thing?

It may be just a buggy, rarely-taken error path in jfs_fill_super that
happened to get caught in the loop code. I'll have to dig through this.

Shaggy

>
> Begin forwarded message:
>
> Date: Fri, 17 Sep 2021 09:33:28 -0700
> From: syzbot <syzbot+ffc4ec...@syzkaller.appspotmail.com>
> To: ak...@linux-foundation.org, linux-...@vger.kernel.org, linu...@kvack.org, syzkall...@googlegroups.com
> Subject: [syzbot] KASAN: use-after-free Read in copy_page_from_iter_atomic

[syzbot]

Auto-closing this bug as obsolete.
Crashes did not happen for a while, no reproducer and no activity.