Re: [syzbot] KASAN: use-after-free Read in jfs_lazycommit

[syzbot <syzbot+885a4f3281b8d99c48d8@syzkaller.appspotmail.com>]

syzbot has found a reproducer for the following issue on:

HEAD commit:    493ffd6605b2 Merge tag 'ucount-rlimits-cleanups-for-v5.19'..
git tree:       upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=165e218a880000
kernel config:  https://syzkaller.appspot.com/x/.config?x=d19f5d16783f901
dashboard link: https://syzkaller.appspot.com/bug?extid=885a4f3281b8d99c48d8
compiler:       Debian clang version 13.0.1-++20220126092033+75e33f71c2da-1~exp1~20220126212112.63, GNU ld (GNU Binutils for Debian) 2.35.2
syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=1523402c880000
C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=15b5fc78880000

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/f1ff6481e26f/disk-493ffd66.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/101bd3c7ae47/vmlinux-493ffd66.xz
mounted in repro: https://storage.googleapis.com/syzbot-assets/9aaa6f9b6f7e/mount_0.gz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+885a4f3281b8d99c48d8@syzkaller.appspotmail.com

ERROR: (device loop0): remounting filesystem as read-only
blkno = 400000, nblocks = 0
ERROR: (device loop0): dbFree: block to be freed is outside the map
==================================================================
BUG: KASAN: use-after-free in jfs_lazycommit+0x746/0xba0 fs/jfs/jfs_txnmgr.c:2730
Read of size 4 at addr ffff88807ee78094 by task jfsCommit/120

CPU: 1 PID: 120 Comm: jfsCommit Not tainted 6.0.0-syzkaller-09423-g493ffd6605b2 #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 09/22/2022
Call Trace:
 <TASK>
 __dump_stack lib/dump_stack.c:88 [inline]
 dump_stack_lvl+0x1b1/0x28e lib/dump_stack.c:106
 print_address_description+0x65/0x4b0 mm/kasan/report.c:317
 print_report+0x108/0x1f0 mm/kasan/report.c:433
 kasan_report+0xc3/0xf0 mm/kasan/report.c:495
 jfs_lazycommit+0x746/0xba0 fs/jfs/jfs_txnmgr.c:2730
 kthread+0x266/0x300 kernel/kthread.c:376
 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:306
 </TASK>

Allocated by task 4321:
 kasan_save_stack mm/kasan/common.c:38 [inline]
 kasan_set_track mm/kasan/common.c:45 [inline]
 set_alloc_info mm/kasan/common.c:437 [inline]
 ____kasan_kmalloc+0xcd/0x100 mm/kasan/common.c:516
 kasan_kmalloc include/linux/kasan.h:234 [inline]
 kmem_cache_alloc_trace+0x97/0x310 mm/slub.c:3289
 kmalloc include/linux/slab.h:600 [inline]
 kzalloc include/linux/slab.h:733 [inline]
 jfs_fill_super+0xfb/0xc50 fs/jfs/super.c:495
 mount_bdev+0x26c/0x3a0 fs/super.c:1400
 legacy_get_tree+0xea/0x180 fs/fs_context.c:610
 vfs_get_tree+0x88/0x270 fs/super.c:1530
 do_new_mount+0x289/0xad0 fs/namespace.c:3040
 do_mount fs/namespace.c:3383 [inline]
 __do_sys_mount fs/namespace.c:3591 [inline]
 __se_sys_mount+0x2d3/0x3c0 fs/namespace.c:3568
 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+0x63/0xcd

Freed by task 3642:
 kasan_save_stack mm/kasan/common.c:38 [inline]
 kasan_set_track+0x3d/0x60 mm/kasan/common.c:45
 kasan_set_free_info+0x1f/0x40 mm/kasan/generic.c:370
 ____kasan_slab_free+0xd8/0x120 mm/kasan/common.c:367
 kasan_slab_free include/linux/kasan.h:200 [inline]
 slab_free_hook mm/slub.c:1759 [inline]
 slab_free_freelist_hook+0x12e/0x1a0 mm/slub.c:1785
 slab_free mm/slub.c:3539 [inline]
 kfree+0xda/0x210 mm/slub.c:4567
 generic_shutdown_super+0x130/0x310 fs/super.c:491
 kill_block_super+0x79/0xd0 fs/super.c:1427
 deactivate_locked_super+0xa7/0xf0 fs/super.c:331
 cleanup_mnt+0x4ce/0x560 fs/namespace.c:1186
 task_work_run+0x146/0x1c0 kernel/task_work.c:177
 resume_user_mode_work include/linux/resume_user_mode.h:49 [inline]
 exit_to_user_mode_loop+0x124/0x150 kernel/entry/common.c:169
 exit_to_user_mode_prepare+0xb2/0x140 kernel/entry/common.c:201
 __syscall_exit_to_user_mode_work kernel/entry/common.c:283 [inline]
 syscall_exit_to_user_mode+0x26/0x60 kernel/entry/common.c:294
 do_syscall_64+0x49/0xb0 arch/x86/entry/common.c:86
 entry_SYSCALL_64_after_hwframe+0x63/0xcd

The buggy address belongs to the object at ffff88807ee78000
 which belongs to the cache kmalloc-256 of size 256
The buggy address is located 148 bytes inside of
 256-byte region [ffff88807ee78000, ffff88807ee78100)

The buggy address belongs to the physical page:
page:ffffea0001fb9e00 refcount:1 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x7ee78
head:ffffea0001fb9e00 order:1 compound_mapcount:0 compound_pincount:0
flags: 0xfff00000010200(slab|head|node=0|zone=1|lastcpupid=0x7ff)
raw: 00fff00000010200 ffffea00004bed80 dead000000000004 ffff888012041b40
raw: 0000000000000000 0000000080100010 00000001ffffffff 0000000000000000
page dumped because: kasan: bad access detected
page_owner tracks the page as allocated
page last allocated via order 1, migratetype Unmovable, gfp_mask 0xd20c0(__GFP_IO|__GFP_FS|__GFP_NOWARN|__GFP_NORETRY|__GFP_COMP|__GFP_NOMEMALLOC), pid 1, tgid 1 (init), ts 11597877098, free_ts 11078632692
 prep_new_page mm/page_alloc.c:2532 [inline]
 get_page_from_freelist+0x742/0x7c0 mm/page_alloc.c:4283
 __alloc_pages+0x259/0x560 mm/page_alloc.c:5549
 alloc_slab_page+0x70/0xf0 mm/slub.c:1829
 allocate_slab+0x5e/0x520 mm/slub.c:1974
 new_slab mm/slub.c:2034 [inline]
 ___slab_alloc+0x3ee/0xc40 mm/slub.c:3036
 __slab_alloc mm/slub.c:3123 [inline]
 slab_alloc_node mm/slub.c:3214 [inline]
 slab_alloc mm/slub.c:3256 [inline]
 __kmalloc+0x2bd/0x370 mm/slub.c:4425
 kmalloc_array include/linux/slab.h:640 [inline]
 kcalloc include/linux/slab.h:671 [inline]
 __list_lru_init+0xa0/0x5f0 mm/list_lru.c:571
 alloc_super+0x7a7/0x920 fs/super.c:272
 sget_fc+0x257/0x6c0 fs/super.c:559
 vfs_get_super fs/super.c:1163 [inline]
 get_tree_nodev+0x26/0x160 fs/super.c:1198
 vfs_get_tree+0x88/0x270 fs/super.c:1530
 do_new_mount+0x289/0xad0 fs/namespace.c:3040
 do_mount fs/namespace.c:3383 [inline]
 __do_sys_mount fs/namespace.c:3591 [inline]
 __se_sys_mount+0x2d3/0x3c0 fs/namespace.c:3568
 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+0x63/0xcd
page last free stack trace:
 reset_page_owner include/linux/page_owner.h:24 [inline]
 free_pages_prepare mm/page_alloc.c:1449 [inline]
 free_pcp_prepare+0x812/0x900 mm/page_alloc.c:1499
 free_unref_page_prepare mm/page_alloc.c:3380 [inline]
 free_unref_page+0x7d/0x5f0 mm/page_alloc.c:3476
 free_contig_range+0xa3/0x160 mm/page_alloc.c:9457
 destroy_args+0xfe/0x91d mm/debug_vm_pgtable.c:1031
 debug_vm_pgtable+0x43e/0x497 mm/debug_vm_pgtable.c:1354
 do_one_initcall+0x1c9/0x400 init/main.c:1296
 do_initcall_level+0x168/0x218 init/main.c:1369
 do_initcalls+0x4b/0x8c init/main.c:1385
 kernel_init_freeable+0x3f1/0x57b init/main.c:1623
 kernel_init+0x19/0x2b0 init/main.c:1512
 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:306

Memory state around the buggy address:
 ffff88807ee77f80: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
 ffff88807ee78000: fa fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>ffff88807ee78080: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
                         ^
 ffff88807ee78100: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
 ffff88807ee78180: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
==================================================================