Re: [syzbot] [fs?] KASAN: slab-use-after-free Read in invalidate_bh_lru

From: Hillf Danton
Date: Fri Sep 13 2024 - 08:34:04 EST

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On Thu, 12 Sep 2024 02:19:26 -0700
> syzbot found the following issue on:
>
> HEAD commit: b31c44928842 Merge tag 'linux_kselftest-kunit-fixes-6.11-r..
> git tree: upstream
> console output: https://syzkaller.appspot.com/x/log.txt?x=12696f29980000
> kernel config: https://syzkaller.appspot.com/x/.config?x=58a85aa6925a8b78
> dashboard link: https://syzkaller.appspot.com/bug?extid=0930d8a3c3c55e931634
> compiler: Debian clang version 15.0.6, GNU ld (GNU Binutils for Debian) 2.40
>
> Unfortunately, I don't have any reproducer for this issue yet.
>
> Downloadable assets:
> disk image (non-bootable): https://storage.googleapis.com/syzbot-assets/7bc7510fe41f/non_bootable_disk-b31c4492.raw.xz
> vmlinux: https://storage.googleapis.com/syzbot-assets/c7a83e0168a1/vmlinux-b31c4492.xz
> kernel image: https://storage.googleapis.com/syzbot-assets/f991c4e68b58/bzImage-b31c4492.xz
>
> IMPORTANT: if you fix the issue, please add the following tag to the commit:
> Reported-by: syzbot+0930d8a3c3c55e931634@xxxxxxxxxxxxxxxxxxxxxxxxx
>
> ==================================================================
> BUG: KASAN: slab-use-after-free in instrument_atomic_read include/linux/instrumented.h:68 [inline]
> BUG: KASAN: slab-use-after-free in atomic_read include/linux/atomic/atomic-instrumented.h:32 [inline]
> BUG: KASAN: slab-use-after-free in __brelse fs/buffer.c:1235 [inline]
> BUG: KASAN: slab-use-after-free in brelse include/linux/buffer_head.h:325 [inline]
> BUG: KASAN: slab-use-after-free in __invalidate_bh_lrus fs/buffer.c:1508 [inline]
> BUG: KASAN: slab-use-after-free in invalidate_bh_lru+0xa8/0x1b0 fs/buffer.c:1521
> Read of size 4 at addr ffff88801c989a58 by task udevd/5114
>
A worse case than the report looks like

buff head is freed and reused with bh lru left intact
flush bh lru
__brelse()
if (atomic_read(&bh->b_count)) {
put_bh(bh);
return;
}

and bh->b_count gets corrupted by put_bh().

> CPU: 0 UID: 0 PID: 5114 Comm: udevd Not tainted 6.11.0-rc6-syzkaller-00308-gb31c44928842 #0
> 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 lib/dump_stack.c:93 [inline]
> dump_stack_lvl+0x241/0x360 lib/dump_stack.c:119
> print_address_description mm/kasan/report.c:377 [inline]
> print_report+0x169/0x550 mm/kasan/report.c:488
> kasan_report+0x143/0x180 mm/kasan/report.c:601
> kasan_check_range+0x282/0x290 mm/kasan/generic.c:189
> instrument_atomic_read include/linux/instrumented.h:68 [inline]
> atomic_read include/linux/atomic/atomic-instrumented.h:32 [inline]
> __brelse fs/buffer.c:1235 [inline]
> brelse include/linux/buffer_head.h:325 [inline]
> __invalidate_bh_lrus fs/buffer.c:1508 [inline]
> invalidate_bh_lru+0xa8/0x1b0 fs/buffer.c:1521
> csd_do_func kernel/smp.c:134 [inline]
> smp_call_function_many_cond+0x15d7/0x29d0 kernel/smp.c:847
> on_each_cpu_cond_mask+0x3f/0x80 kernel/smp.c:1023
> kill_bdev block/bdev.c:89 [inline]
> blkdev_flush_mapping+0xfe/0x250 block/bdev.c:664
> blkdev_put_whole block/bdev.c:671 [inline]
> bdev_release+0x466/0x700 block/bdev.c:1096
> blkdev_release+0x15/0x20 block/fops.c:638
> __fput+0x24a/0x8a0 fs/file_table.c:422
> __do_sys_close fs/open.c:1566 [inline]
> __se_sys_close fs/open.c:1551 [inline]
> __x64_sys_close+0x7f/0x110 fs/open.c:1551
> do_syscall_x64 arch/x86/entry/common.c:52 [inline]
> do_syscall_64+0xf3/0x230 arch/x86/entry/common.c:83
> entry_SYSCALL_64_after_hwframe+0x77/0x7f
> RIP: 0033:0x7f8226f170a8
> Code: 48 8b 05 83 9d 0d 00 64 c7 00 16 00 00 00 83 c8 ff 48 83 c4 20 5b c3 64 8b 04 25 18 00 00 00 85 c0 75 20 b8 03 00 00 00 0f 05 <48> 3d 00 f0 ff ff 76 5b 48 8b 15 51 9d 0d 00 f7 d8 64 89 02 48 83
> RSP: 002b:00007ffe0319be58 EFLAGS: 00000246 ORIG_RAX: 0000000000000003
> RAX: ffffffffffffffda RBX: 00007f8226dee0e0 RCX: 00007f8226f170a8
> RDX: 000056579a6766d5 RSI: 00007ffe0319b658 RDI: 0000000000000008
> RBP: 00005652ff487f60 R08: 0000000000000006 R09: b595b5b875e4bbae
> R10: 000000000000010f R11: 0000000000000246 R12: 0000000000000002
> R13: 00005652ff478840 R14: 0000000000000008 R15: 00005652ff466910
> </TASK>
>
> Allocated by task 5112:
> kasan_save_stack mm/kasan/common.c:47 [inline]
> kasan_save_track+0x3f/0x80 mm/kasan/common.c:68
> unpoison_slab_object mm/kasan/common.c:312 [inline]
> __kasan_slab_alloc+0x66/0x80 mm/kasan/common.c:338
> kasan_slab_alloc include/linux/kasan.h:201 [inline]
> slab_post_alloc_hook mm/slub.c:3992 [inline]
> slab_alloc_node mm/slub.c:4041 [inline]
> kmem_cache_alloc_noprof+0x135/0x2a0 mm/slub.c:4048
> alloc_buffer_head+0x2a/0x290 fs/buffer.c:3025
> folio_alloc_buffers+0x241/0x5b0 fs/buffer.c:929
> grow_dev_folio fs/buffer.c:1072 [inline]
> grow_buffers fs/buffer.c:1113 [inline]
> __getblk_slow fs/buffer.c:1139 [inline]
> bdev_getblk+0x2a6/0x550 fs/buffer.c:1441
> __bread_gfp+0x86/0x400 fs/buffer.c:1495
> sb_bread include/linux/buffer_head.h:347 [inline]
> sysv_fill_super+0x231/0x710 fs/sysv/super.c:379
> mount_bdev+0x20a/0x2d0 fs/super.c:1679
> legacy_get_tree+0xee/0x190 fs/fs_context.c:662
> vfs_get_tree+0x90/0x2b0 fs/super.c:1800
> do_new_mount+0x2be/0xb40 fs/namespace.c:3472
> do_mount fs/namespace.c:3812 [inline]
> __do_sys_mount fs/namespace.c:4020 [inline]
> __se_sys_mount+0x2d6/0x3c0 fs/namespace.c:3997
> do_syscall_x64 arch/x86/entry/common.c:52 [inline]
> do_syscall_64+0xf3/0x230 arch/x86/entry/common.c:83
> entry_SYSCALL_64_after_hwframe+0x77/0x7f
>
> Freed by task 79:
> kasan_save_stack mm/kasan/common.c:47 [inline]
> kasan_save_track+0x3f/0x80 mm/kasan/common.c:68
> kasan_save_free_info+0x40/0x50 mm/kasan/generic.c:579
> poison_slab_object+0xe0/0x150 mm/kasan/common.c:240
> __kasan_slab_free+0x37/0x60 mm/kasan/common.c:256
> kasan_slab_free include/linux/kasan.h:184 [inline]
> slab_free_hook mm/slub.c:2256 [inline]
> slab_free mm/slub.c:4477 [inline]
> kmem_cache_free+0x145/0x350 mm/slub.c:4552
> free_buffer_head+0x54/0x240 fs/buffer.c:3041
> try_to_free_buffers+0x311/0x5f0 fs/buffer.c:2982
> shrink_folio_list+0x26c2/0x8c90 mm/vmscan.c:1413
> evict_folios+0x50f7/0x7780 mm/vmscan.c:4560
> try_to_shrink_lruvec+0x9ab/0xbb0 mm/vmscan.c:4755
> shrink_one+0x3b9/0x850 mm/vmscan.c:4793
> shrink_many mm/vmscan.c:4856 [inline]
> lru_gen_shrink_node mm/vmscan.c:4934 [inline]
> shrink_node+0x3799/0x3de0 mm/vmscan.c:5914
> kswapd_shrink_node mm/vmscan.c:6742 [inline]
> balance_pgdat mm/vmscan.c:6934 [inline]
> kswapd+0x1cbc/0x3720 mm/vmscan.c:7203
> kthread+0x2f0/0x390 kernel/kthread.c:389
> ret_from_fork+0x4b/0x80 arch/x86/kernel/process.c:147
> ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:244
>
> The buggy address belongs to the object at ffff88801c9899f8
> which belongs to the cache buffer_head of size 168
> The buggy address is located 96 bytes inside of
> freed 168-byte region [ffff88801c9899f8, ffff88801c989aa0)
>
> The buggy address belongs to the physical page:
> page: refcount:1 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x1c989
> flags: 0xfff00000000000(node=0|zone=1|lastcpupid=0x7ff)
> page_type: 0xfdffffff(slab)
> raw: 00fff00000000000 ffff88801b763c80 ffffea0000725d40 0000000000000006
> raw: 0000000000000000 0000000080110011 00000001fdffffff 0000000000000000
> page dumped because: kasan: bad access detected
> page_owner tracks the page as allocated
> page last allocated via order 0, migratetype Reclaimable, gfp_mask 0x152c50(GFP_NOFS|__GFP_NOWARN|__GFP_NORETRY|__GFP_COMP|__GFP_HARDWALL|__GFP_RECLAIMABLE), pid 1, tgid 1 (init), ts 28576033639, free_ts 0
> set_page_owner include/linux/page_owner.h:32 [inline]
> post_alloc_hook+0x1f3/0x230 mm/page_alloc.c:1500
> prep_new_page mm/page_alloc.c:1508 [inline]
> get_page_from_freelist+0x2e4c/0x2f10 mm/page_alloc.c:3446
> __alloc_pages_noprof+0x256/0x6c0 mm/page_alloc.c:4702
> __alloc_pages_node_noprof include/linux/gfp.h:269 [inline]
> alloc_pages_node_noprof include/linux/gfp.h:296 [inline]
> alloc_slab_page+0x5f/0x120 mm/slub.c:2325
> allocate_slab+0x5a/0x2f0 mm/slub.c:2488
> new_slab mm/slub.c:2541 [inline]
> ___slab_alloc+0xcd1/0x14b0 mm/slub.c:3727
> __slab_alloc+0x58/0xa0 mm/slub.c:3817
> __slab_alloc_node mm/slub.c:3870 [inline]
> slab_alloc_node mm/slub.c:4029 [inline]
> kmem_cache_alloc_noprof+0x1c1/0x2a0 mm/slub.c:4048
> alloc_buffer_head+0x2a/0x290 fs/buffer.c:3025
> folio_alloc_buffers+0x241/0x5b0 fs/buffer.c:929
> grow_dev_folio fs/buffer.c:1072 [inline]
> grow_buffers fs/buffer.c:1113 [inline]
> __getblk_slow fs/buffer.c:1139 [inline]
> bdev_getblk+0x2a6/0x550 fs/buffer.c:1441
> __getblk include/linux/buffer_head.h:381 [inline]
> sb_getblk include/linux/buffer_head.h:387 [inline]
> ext4_read_inode_bitmap+0x24c/0x12f0 fs/ext4/ialloc.c:145
> __ext4_new_inode+0x106f/0x4260 fs/ext4/ialloc.c:1054
> ext4_create+0x279/0x550 fs/ext4/namei.c:2832
> lookup_open fs/namei.c:3578 [inline]
> open_last_lookups fs/namei.c:3647 [inline]
> path_openat+0x1a9a/0x3470 fs/namei.c:3883
> do_filp_open+0x235/0x490 fs/namei.c:3913
> page_owner free stack trace missing
>
> Memory state around the buggy address:
> ffff88801c989900: fc fc fa fb fb fb fb fb fb fb fb fb fb fb fb fb
> ffff88801c989980: fb fb fb fb fb fb fb fc fc fc fc fc fc fc fc fa
> >ffff88801c989a00: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
> ^
> ffff88801c989a80: fb fb fb fb fc fc fc fc fc fc fc fc 00 00 00 00
> ffff88801c989b00: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
> ==================================================================

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In reply to: syzbot: "[syzbot] [fs?] KASAN: slab-use-after-free Read in invalidate_bh_lru"
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