Message-ID: <6762f991.050a0220.29fcd0.0098.GAE@google.com>
Date: Wed, 18 Dec 2024 08:34:25 -0800
From: syzbot <syzbot+5970f72a85a751ab7556@...kaller.appspotmail.com>
To: kent.overstreet@...ux.dev, linux-bcachefs@...r.kernel.org, 
	linux-kernel@...r.kernel.org, syzkaller-bugs@...glegroups.com
Subject: Re: [syzbot] [bcachefs?] KASAN: use-after-free Read in bkey_packed_valid

syzbot has found a reproducer for the following issue on:

HEAD commit:    aef25be35d23 hexagon: Disable constant extender optimizati..
git tree:       upstream
console+strace: https://syzkaller.appspot.com/x/log.txt?x=173a37e8580000
kernel config:  https://syzkaller.appspot.com/x/.config?x=1234f097ee657d8b
dashboard link: https://syzkaller.appspot.com/bug?extid=5970f72a85a751ab7556
compiler:       Debian clang version 15.0.6, GNU ld (GNU Binutils for Debian) 2.40
syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=15c06f44580000
C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=10ba37e8580000

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/ba5aa1dfe5fd/disk-aef25be3.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/f4809d9d3d5b/vmlinux-aef25be3.xz
kernel image: https://storage.googleapis.com/syzbot-assets/d6becddf1bcb/bzImage-aef25be3.xz
mounted in repro: https://storage.googleapis.com/syzbot-assets/deb86d739e78/mount_0.gz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+5970f72a85a751ab7556@...kaller.appspotmail.com

bcachefs (loop0): error validating btree node at btree subvolumes level 0/0
  u64s 11 type btree_ptr_v2 SPOS_MAX len 0 ver 0: seq c0bef60d07ceb940 written 960 min_key POS_MIN durability: 1 ptr: 0:35:0 gen 0  
  node offset 8/960 bset u64s 60677 bset byte offset 40: bad k->u64s 0 (min 3 max 253), fixing
==================================================================
BUG: KASAN: slab-use-after-free in bkey_packed_valid+0x3a8/0x4b0 fs/bcachefs/btree_io.c:847
Read of size 1 at addr ffff888078f20000 by task kworker/0:2H/5961

CPU: 0 UID: 0 PID: 5961 Comm: kworker/0:2H Not tainted 6.13.0-rc3-syzkaller-00044-gaef25be35d23 #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 11/25/2024
Workqueue: bcachefs_btree_read_complete btree_node_read_work
Call Trace:
 <TASK>
 __dump_stack lib/dump_stack.c:94 [inline]
 dump_stack_lvl+0x241/0x360 lib/dump_stack.c:120
 print_address_description mm/kasan/report.c:378 [inline]
 print_report+0x169/0x550 mm/kasan/report.c:489
 kasan_report+0x143/0x180 mm/kasan/report.c:602
 bkey_packed_valid+0x3a8/0x4b0 fs/bcachefs/btree_io.c:847
 validate_bset_keys+0x98d/0x1610 fs/bcachefs/btree_io.c:955
 bch2_btree_node_read_done+0x2402/0x5e90 fs/bcachefs/btree_io.c:1130
 btree_node_read_work+0x68b/0x1260 fs/bcachefs/btree_io.c:1323
 process_one_work kernel/workqueue.c:3229 [inline]
 process_scheduled_works+0xa66/0x1840 kernel/workqueue.c:3310
 worker_thread+0x870/0xd30 kernel/workqueue.c:3391
 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
 </TASK>

Allocated by task 5909:
 kasan_save_stack mm/kasan/common.c:47 [inline]
 kasan_save_track+0x3f/0x80 mm/kasan/common.c:68
 poison_kmalloc_redzone mm/kasan/common.c:377 [inline]
 __kasan_kmalloc+0x98/0xb0 mm/kasan/common.c:394
 kasan_kmalloc include/linux/kasan.h:260 [inline]
 __do_kmalloc_node mm/slub.c:4298 [inline]
 __kmalloc_node_noprof+0x290/0x4d0 mm/slub.c:4304
 __kvmalloc_node_noprof+0x72/0x190 mm/util.c:650
 btree_node_data_alloc+0x15a/0x260 fs/bcachefs/btree_cache.c:157
 __bch2_btree_node_mem_alloc+0x1d8/0x3e0 fs/bcachefs/btree_cache.c:198
 bch2_fs_btree_cache_init+0x26f/0x630 fs/bcachefs/btree_cache.c:653
 bch2_fs_alloc fs/bcachefs/super.c:917 [inline]
 bch2_fs_open+0x2aa4/0x2f80 fs/bcachefs/super.c:2065
 bch2_fs_get_tree+0x738/0x1710 fs/bcachefs/fs.c:2157
 vfs_get_tree+0x90/0x2b0 fs/super.c:1814
 do_new_mount+0x2be/0xb40 fs/namespace.c:3507
 do_mount fs/namespace.c:3847 [inline]
 __do_sys_mount fs/namespace.c:4057 [inline]
 __se_sys_mount+0x2d6/0x3c0 fs/namespace.c:4034
 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 5909:
 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:582
 poison_slab_object mm/kasan/common.c:247 [inline]
 __kasan_slab_free+0x59/0x70 mm/kasan/common.c:264
 kasan_slab_free include/linux/kasan.h:233 [inline]
 slab_free_hook mm/slub.c:2353 [inline]
 slab_free mm/slub.c:4613 [inline]
 kfree+0x196/0x430 mm/slub.c:4761
 __btree_node_data_free+0x341/0x550 fs/bcachefs/btree_cache.c:113
 btree_node_data_free fs/bcachefs/btree_cache.c:127 [inline]
 bch2_fs_btree_cache_exit+0xb1b/0x1530 fs/bcachefs/btree_cache.c:610
 __bch2_fs_free fs/bcachefs/super.c:557 [inline]
 bch2_fs_release+0x20e/0x7d0 fs/bcachefs/super.c:611
 kobject_cleanup lib/kobject.c:689 [inline]
 kobject_release lib/kobject.c:720 [inline]
 kref_put include/linux/kref.h:65 [inline]
 kobject_put+0x22f/0x480 lib/kobject.c:737
 bch2_fs_alloc fs/bcachefs/super.c:960 [inline]
 bch2_fs_open+0x1ebe/0x2f80 fs/bcachefs/super.c:2065
 bch2_fs_get_tree+0x738/0x1710 fs/bcachefs/fs.c:2157
 vfs_get_tree+0x90/0x2b0 fs/super.c:1814
 do_new_mount+0x2be/0xb40 fs/namespace.c:3507
 do_mount fs/namespace.c:3847 [inline]
 __do_sys_mount fs/namespace.c:4057 [inline]
 __se_sys_mount+0x2d6/0x3c0 fs/namespace.c:4034
 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

The buggy address belongs to the object at ffff888078f20000
 which belongs to the cache kmalloc-rcl-512 of size 512
The buggy address is located 0 bytes inside of
 freed 512-byte region [ffff888078f20000, ffff888078f20200)

The buggy address belongs to the physical page:
page: refcount:1 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x78f20
head: order:2 mapcount:0 entire_mapcount:0 nr_pages_mapped:0 pincount:0
flags: 0xfff00000000040(head|node=0|zone=1|lastcpupid=0x7ff)
page_type: f5(slab)
raw: 00fff00000000040 ffff88801ac42dc0 dead000000000122 0000000000000000
raw: 0000000000000000 0000000000100010 00000001f5000000 0000000000000000
head: 00fff00000000040 ffff88801ac42dc0 dead000000000122 0000000000000000
head: 0000000000000000 0000000000100010 00000001f5000000 0000000000000000
head: 00fff00000000002 ffffea0001e3c801 ffffffffffffffff 0000000000000000
head: 0000000000000004 0000000000000000 00000000ffffffff 0000000000000000
page dumped because: kasan: bad access detected
page_owner tracks the page as allocated
page last allocated via order 2, migratetype Reclaimable, gfp_mask 0xd20d0(__GFP_IO|__GFP_FS|__GFP_NOWARN|__GFP_NORETRY|__GFP_COMP|__GFP_NOMEMALLOC|__GFP_RECLAIMABLE), pid 5909, tgid 5909 (syz-executor238), ts 94208745569, free_ts 92197228717
 set_page_owner include/linux/page_owner.h:32 [inline]
 post_alloc_hook+0x1f3/0x230 mm/page_alloc.c:1556
 prep_new_page mm/page_alloc.c:1564 [inline]
 get_page_from_freelist+0x3651/0x37a0 mm/page_alloc.c:3474
 __alloc_pages_noprof+0x292/0x710 mm/page_alloc.c:4751
 alloc_pages_mpol_noprof+0x3e8/0x680 mm/mempolicy.c:2269
 alloc_slab_page+0x6a/0x110 mm/slub.c:2423
 allocate_slab+0x5a/0x2b0 mm/slub.c:2589
 new_slab mm/slub.c:2642 [inline]
 ___slab_alloc+0xc27/0x14a0 mm/slub.c:3830
 __slab_alloc+0x58/0xa0 mm/slub.c:3920
 __slab_alloc_node mm/slub.c:3995 [inline]
 slab_alloc_node mm/slub.c:4156 [inline]
 __do_kmalloc_node mm/slub.c:4297 [inline]
 __kmalloc_node_noprof+0x2ee/0x4d0 mm/slub.c:4304
 __kvmalloc_node_noprof+0x72/0x190 mm/util.c:650
 btree_node_data_alloc+0x15a/0x260 fs/bcachefs/btree_cache.c:157
 __bch2_btree_node_mem_alloc+0x1d8/0x3e0 fs/bcachefs/btree_cache.c:198
 bch2_fs_btree_cache_init+0x26f/0x630 fs/bcachefs/btree_cache.c:653
 bch2_fs_alloc fs/bcachefs/super.c:917 [inline]
 bch2_fs_open+0x2aa4/0x2f80 fs/bcachefs/super.c:2065
 bch2_fs_get_tree+0x738/0x1710 fs/bcachefs/fs.c:2157
 vfs_get_tree+0x90/0x2b0 fs/super.c:1814
page last free pid 5877 tgid 5877 stack trace:
 reset_page_owner include/linux/page_owner.h:25 [inline]
 free_pages_prepare mm/page_alloc.c:1127 [inline]
 free_unref_page+0xd2c/0x1000 mm/page_alloc.c:2657
 __folio_put+0x2b3/0x360 mm/swap.c:112
 folio_put include/linux/mm.h:1488 [inline]
 free_large_kmalloc+0xfe/0x180 mm/slub.c:4732
 kfree+0x212/0x430 mm/slub.c:4755
 __btree_node_data_free+0x30e/0x550 fs/bcachefs/btree_cache.c:110
 btree_node_data_free fs/bcachefs/btree_cache.c:127 [inline]
 bch2_fs_btree_cache_exit+0xb1b/0x1530 fs/bcachefs/btree_cache.c:610
 __bch2_fs_free fs/bcachefs/super.c:557 [inline]
 bch2_fs_release+0x20e/0x7d0 fs/bcachefs/super.c:611
 kobject_cleanup lib/kobject.c:689 [inline]
 kobject_release lib/kobject.c:720 [inline]
 kref_put include/linux/kref.h:65 [inline]
 kobject_put+0x22f/0x480 lib/kobject.c:737
 bch2_fs_alloc fs/bcachefs/super.c:960 [inline]
 bch2_fs_open+0x1ebe/0x2f80 fs/bcachefs/super.c:2065
 bch2_fs_get_tree+0x738/0x1710 fs/bcachefs/fs.c:2157
 vfs_get_tree+0x90/0x2b0 fs/super.c:1814
 do_new_mount+0x2be/0xb40 fs/namespace.c:3507
 do_mount fs/namespace.c:3847 [inline]
 __do_sys_mount fs/namespace.c:4057 [inline]
 __se_sys_mount+0x2d6/0x3c0 fs/namespace.c:4034
 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

Memory state around the buggy address:
 ffff888078f1ff00: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
 ffff888078f1ff80: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
>ffff888078f20000: fa fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
                   ^
 ffff888078f20080: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff888078f20100: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
==================================================================


---
If you want syzbot to run the reproducer, reply with:
#syz test: git://repo/address.git branch-or-commit-hash
If you attach or paste a git patch, syzbot will apply it before testing.

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