Re: [syzbot] [btrfs?] KASAN: slab-use-after-free Read in btrfs_open_devices

[syzbot]

Hello,

syzbot has tested the proposed patch but the reproducer is still triggering an issue:
KASAN: use-after-free Read in percpu_counter_destroy

BTRFS error (device loop3): open_ctree failed
==================================================================
BUG: KASAN: use-after-free in percpu_counter_destroy+0x47/0x50 lib/percpu_counter.c:182
Read of size 8 at addr ffff88807307d030 by task syz-executor.3/5615

CPU: 0 PID: 5615 Comm: syz-executor.3 Not tainted 6.5.0-rc5-next-20230807-syzkaller-dirty #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/26/2023
Call Trace:
 <TASK>
 __dump_stack lib/dump_stack.c:88 [inline]
 dump_stack_lvl+0xd9/0x1b0 lib/dump_stack.c:106
 print_address_description mm/kasan/report.c:364 [inline]
 print_report+0xc4/0x620 mm/kasan/report.c:475
 kasan_report+0xda/0x110 mm/kasan/report.c:588
 percpu_counter_destroy+0x47/0x50 lib/percpu_counter.c:182
 btrfs_free_fs_info+0x1c/0x380 fs/btrfs/disk-io.c:1246
 btrfs_mount_root+0x3ea/0xe60 fs/btrfs/super.c:1544
 legacy_get_tree+0x109/0x220 fs/fs_context.c:611
 vfs_get_tree+0x88/0x350 fs/super.c:1544
 fc_mount fs/namespace.c:1112 [inline]
 vfs_kern_mount.part.0+0xcb/0x170 fs/namespace.c:1142
 vfs_kern_mount+0x3f/0x60 fs/namespace.c:1129
 btrfs_mount+0x292/0xb10 fs/btrfs/super.c:1587
 legacy_get_tree+0x109/0x220 fs/fs_context.c:611
 vfs_get_tree+0x88/0x350 fs/super.c:1544
 do_new_mount fs/namespace.c:3335 [inline]
 path_mount+0x1492/0x1ed0 fs/namespace.c:3662
 do_mount fs/namespace.c:3675 [inline]
 __do_sys_mount fs/namespace.c:3884 [inline]
 __se_sys_mount fs/namespace.c:3861 [inline]
 __x64_sys_mount+0x293/0x310 fs/namespace.c:3861
 do_syscall_x64 arch/x86/entry/common.c:50 [inline]
 do_syscall_64+0x38/0xb0 arch/x86/entry/common.c:80
 entry_SYSCALL_64_after_hwframe+0x63/0xcd
RIP: 0033:0x7f8b6847e1ea
Code: d8 64 89 02 48 c7 c0 ff ff ff ff eb a6 e8 de 09 00 00 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 40 00 49 89 ca b8 a5 00 00 00 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 c7 c1 b0 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007f8b691f0ee8 EFLAGS: 00000246 ORIG_RAX: 00000000000000a5
RAX: ffffffffffffffda RBX: 00007f8b691f0f80 RCX: 00007f8b6847e1ea
RDX: 00000000200051c0 RSI: 0000000020005200 RDI: 00007f8b691f0f40
RBP: 00000000200051c0 R08: 00007f8b691f0f80 R09: 0000000001000008
R10: 0000000001000008 R11: 0000000000000246 R12: 0000000020005200
R13: 00007f8b691f0f40 R14: 00000000000051ab R15: 0000000020000280
 </TASK>

The buggy address belongs to the physical page:
page:ffffea0001cc1f40 refcount:0 mapcount:0 mapping:0000000000000000 index:0x4 pfn:0x7307d
flags: 0xfff00000000000(node=0|zone=1|lastcpupid=0x7ff)
page_type: 0xffffffff()
raw: 00fff00000000000 0000000000000000 ffffffff00000201 0000000000000000
raw: 0000000000000004 0000000000000000 00000000ffffffff 0000000000000000
page dumped because: kasan: bad access detected
page_owner tracks the page as freed
page last allocated via order 2, migratetype Unmovable, gfp_mask 0x152dc0(GFP_USER|__GFP_NOWARN|__GFP_NORETRY|__GFP_COMP|__GFP_ZERO), pid 5615, tgid 5614 (syz-executor.3), ts 74051625164, free_ts 74183131126
 set_page_owner include/linux/page_owner.h:31 [inline]
 post_alloc_hook+0x2d2/0x350 mm/page_alloc.c:1567
 prep_new_page mm/page_alloc.c:1574 [inline]
 get_page_from_freelist+0x10d7/0x31b0 mm/page_alloc.c:3253
 __alloc_pages+0x1d0/0x4a0 mm/page_alloc.c:4509
 __alloc_pages_node include/linux/gfp.h:237 [inline]
 alloc_pages_node include/linux/gfp.h:260 [inline]
 __kmalloc_large_node+0x87/0x1c0 mm/slab_common.c:1164
 __do_kmalloc_node mm/slab_common.c:1011 [inline]
 __kmalloc_node.cold+0x5/0xdd mm/slab_common.c:1030
 kmalloc_node include/linux/slab.h:619 [inline]
 kvmalloc_node+0x6f/0x1a0 mm/util.c:604
 kvmalloc include/linux/slab.h:737 [inline]
 kvzalloc include/linux/slab.h:745 [inline]
 btrfs_mount_root+0xf4/0xe60 fs/btrfs/super.c:1462
 legacy_get_tree+0x109/0x220 fs/fs_context.c:611
 vfs_get_tree+0x88/0x350 fs/super.c:1544
 fc_mount fs/namespace.c:1112 [inline]
 vfs_kern_mount.part.0+0xcb/0x170 fs/namespace.c:1142
 vfs_kern_mount+0x3f/0x60 fs/namespace.c:1129
 btrfs_mount+0x292/0xb10 fs/btrfs/super.c:1587
 legacy_get_tree+0x109/0x220 fs/fs_context.c:611
 vfs_get_tree+0x88/0x350 fs/super.c:1544
 do_new_mount fs/namespace.c:3335 [inline]
 path_mount+0x1492/0x1ed0 fs/namespace.c:3662
 do_mount fs/namespace.c:3675 [inline]
 __do_sys_mount fs/namespace.c:3884 [inline]
 __se_sys_mount fs/namespace.c:3861 [inline]
 __x64_sys_mount+0x293/0x310 fs/namespace.c:3861
page last free stack trace:
 reset_page_owner include/linux/page_owner.h:24 [inline]
 free_pages_prepare mm/page_alloc.c:1158 [inline]
 free_unref_page_prepare+0x508/0xb90 mm/page_alloc.c:2380
 free_unref_page+0x33/0x3b0 mm/page_alloc.c:2475
 kvfree+0x47/0x50 mm/util.c:650
 deactivate_locked_super+0x9a/0x170 fs/super.c:330
 btrfs_mount_root+0x62d/0xe60 fs/btrfs/super.c:1533
 legacy_get_tree+0x109/0x220 fs/fs_context.c:611
 vfs_get_tree+0x88/0x350 fs/super.c:1544
 fc_mount fs/namespace.c:1112 [inline]
 vfs_kern_mount.part.0+0xcb/0x170 fs/namespace.c:1142
 vfs_kern_mount+0x3f/0x60 fs/namespace.c:1129
 btrfs_mount+0x292/0xb10 fs/btrfs/super.c:1587
 legacy_get_tree+0x109/0x220 fs/fs_context.c:611
 vfs_get_tree+0x88/0x350 fs/super.c:1544
 do_new_mount fs/namespace.c:3335 [inline]
 path_mount+0x1492/0x1ed0 fs/namespace.c:3662
 do_mount fs/namespace.c:3675 [inline]
 __do_sys_mount fs/namespace.c:3884 [inline]
 __se_sys_mount fs/namespace.c:3861 [inline]
 __x64_sys_mount+0x293/0x310 fs/namespace.c:3861
 do_syscall_x64 arch/x86/entry/common.c:50 [inline]
 do_syscall_64+0x38/0xb0 arch/x86/entry/common.c:80
 entry_SYSCALL_64_after_hwframe+0x63/0xcd

Memory state around the buggy address:
 ffff88807307cf00: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
 ffff88807307cf80: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
>ffff88807307d000: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
                                     ^
 ffff88807307d080: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
 ffff88807307d100: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
==================================================================


Tested on:

commit:         f7dc24b3 Add linux-next specific files for 20230807
git tree:       https://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git
console output: https://syzkaller.appspot.com/x/log.txt?x=10e4c645a80000
kernel config:  https://syzkaller.appspot.com/x/.config?x=d7847c9dca13d6c5
dashboard link: https://syzkaller.appspot.com/bug?extid=26860029a4d562566231
compiler:       gcc (Debian 12.2.0-14) 12.2.0, GNU ld (GNU Binutils for Debian) 2.40
patch:          https://syzkaller.appspot.com/x/patch.diff?x=15c512b3a80000