syzbot


KASAN: use-after-free Read in flush_nat_entries

Status: upstream: reported C repro on 2023/02/12 05:18
Subsystems: f2fs
[Documentation on labels]
Reported-by: syzbot+042d27b5c9f7eb3bd228@syzkaller.appspotmail.com
First crash: 492d, last: 492d

Sample crash report:
F2FS-fs (loop0): Can't find valid F2FS filesystem in 1th superblock
F2FS-fs (loop0): invalid crc value
F2FS-fs (loop0): Found nat_bits in checkpoint
F2FS-fs (loop0): Mounted with checkpoint version = 753bd00b
==================================================================
BUG: KASAN: use-after-free in f2fs_test_bit fs/f2fs/f2fs.h:1928 [inline]
BUG: KASAN: use-after-free in current_nat_addr fs/f2fs/node.h:215 [inline]
BUG: KASAN: use-after-free in get_next_nat_page fs/f2fs/node.c:133 [inline]
BUG: KASAN: use-after-free in __flush_nat_entry_set fs/f2fs/node.c:2480 [inline]
BUG: KASAN: use-after-free in flush_nat_entries+0x2190/0x25e0 fs/f2fs/node.c:2571
Read of size 1 at addr ffff8880aacb1610 by task syz-executor477/7971

CPU: 1 PID: 7971 Comm: syz-executor477 Not tainted 4.14.305-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/21/2023
Call Trace:
 __dump_stack lib/dump_stack.c:17 [inline]
 dump_stack+0x1b2/0x281 lib/dump_stack.c:58
 print_address_description.cold+0x54/0x1d3 mm/kasan/report.c:251
 kasan_report_error.cold+0x8a/0x191 mm/kasan/report.c:350
 kasan_report mm/kasan/report.c:408 [inline]
 __asan_report_load1_noabort+0x68/0x70 mm/kasan/report.c:426
 f2fs_test_bit fs/f2fs/f2fs.h:1928 [inline]
 current_nat_addr fs/f2fs/node.h:215 [inline]
 get_next_nat_page fs/f2fs/node.c:133 [inline]
 __flush_nat_entry_set fs/f2fs/node.c:2480 [inline]
 flush_nat_entries+0x2190/0x25e0 fs/f2fs/node.c:2571
 write_checkpoint+0x311/0x45f0 fs/f2fs/checkpoint.c:1411
 f2fs_sync_fs+0x178/0x3f0 fs/f2fs/super.c:873
 __sync_filesystem fs/sync.c:39 [inline]
 sync_filesystem fs/sync.c:67 [inline]
 sync_filesystem+0x185/0x230 fs/sync.c:48
 generic_shutdown_super+0x70/0x370 fs/super.c:432
 kill_block_super+0x95/0xe0 fs/super.c:1161
 deactivate_locked_super+0x6c/0xd0 fs/super.c:319
 deactivate_super+0x7f/0xa0 fs/super.c:350
 cleanup_mnt+0x186/0x2c0 fs/namespace.c:1183
 task_work_run+0x11f/0x190 kernel/task_work.c:113
 exit_task_work include/linux/task_work.h:22 [inline]
 do_exit+0xa44/0x2850 kernel/exit.c:915
 do_group_exit+0x100/0x2e0 kernel/exit.c:1037
 SYSC_exit_group kernel/exit.c:1048 [inline]
 SyS_exit_group+0x19/0x20 kernel/exit.c:1046
 do_syscall_64+0x1d5/0x640 arch/x86/entry/common.c:292
 entry_SYSCALL_64_after_hwframe+0x5e/0xd3
RIP: 0033:0x7f3ee670e9d9
RSP: 002b:00007ffd3cd3efa8 EFLAGS: 00000246 ORIG_RAX: 00000000000000e7
RAX: ffffffffffffffda RBX: 00007f3ee678b330 RCX: 00007f3ee670e9d9
RDX: 000000000000003c RSI: 00000000000000e7 RDI: 0000000000000001
RBP: 0000000000000001 R08: ffffffffffffffc0 R09: 00007f3ee6785e40
R10: 00007ffd3cd3eec0 R11: 0000000000000246 R12: 00007f3ee678b330
R13: 0000000000000001 R14: 0000000000000000 R15: 0000000000000001

Allocated by task 7931:
 save_stack mm/kasan/kasan.c:447 [inline]
 set_track mm/kasan/kasan.c:459 [inline]
 kasan_kmalloc+0xeb/0x160 mm/kasan/kasan.c:551
 kmem_cache_alloc+0x124/0x3c0 mm/slab.c:3552
 getname_flags+0xc8/0x550 fs/namei.c:138
 user_path_at_empty+0x2a/0x50 fs/namei.c:2631
 user_path_at include/linux/namei.h:57 [inline]
 user_statfs+0x78/0x110 fs/statfs.c:87
 SYSC_statfs fs/statfs.c:179 [inline]
 SyS_statfs+0x65/0xb0 fs/statfs.c:176
 do_syscall_64+0x1d5/0x640 arch/x86/entry/common.c:292
 entry_SYSCALL_64_after_hwframe+0x5e/0xd3

Freed by task 7931:
 save_stack mm/kasan/kasan.c:447 [inline]
 set_track mm/kasan/kasan.c:459 [inline]
 kasan_slab_free+0xc3/0x1a0 mm/kasan/kasan.c:524
 __cache_free mm/slab.c:3496 [inline]
 kmem_cache_free+0x7c/0x2b0 mm/slab.c:3758
 putname+0xcd/0x110 fs/namei.c:259
 filename_lookup+0x37b/0x510 fs/namei.c:2386
 user_path_at include/linux/namei.h:57 [inline]
 user_statfs+0x78/0x110 fs/statfs.c:87
 SYSC_statfs fs/statfs.c:179 [inline]
 SyS_statfs+0x65/0xb0 fs/statfs.c:176
 do_syscall_64+0x1d5/0x640 arch/x86/entry/common.c:292
 entry_SYSCALL_64_after_hwframe+0x5e/0xd3

The buggy address belongs to the object at ffff8880aacb0b00
 which belongs to the cache names_cache of size 4096
The buggy address is located 2832 bytes inside of
 4096-byte region [ffff8880aacb0b00, ffff8880aacb1b00)
The buggy address belongs to the page:
page:ffffea0002ab2c00 count:1 mapcount:0 mapping:ffff8880aacb0b00 index:0x0 compound_mapcount: 0
flags: 0xfff00000008100(slab|head)
raw: 00fff00000008100 ffff8880aacb0b00 0000000000000000 0000000100000001
raw: ffffea0002ab2ca0 ffffea00024eeca0 ffff88823f8c1200 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
 ffff8880aacb1500: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff8880aacb1580: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>ffff8880aacb1600: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
                         ^
 ffff8880aacb1680: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff8880aacb1700: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
==================================================================

Crashes (1):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2023/02/12 05:18 linux-4.14.y a8ad60f2af58 93e26d60 .config console log report syz C [disk image] [vmlinux] [kernel image] [mounted in repro] ci2-linux-4-14 KASAN: use-after-free Read in flush_nat_entries
* Struck through repros no longer work on HEAD.