Re: [syzbot] [btrfs?] KASAN: slab-out-of-bounds Read in getname_kernel (2)

[syzbot]

Hello,

syzbot has tested the proposed patch but the reproducer is still triggering an issue:
KASAN: slab-out-of-bounds Read in btrfs_dev_replace_by_ioctl

BTRFS info (device loop0): disabling free space tree
BTRFS info (device loop0): clearing compat-ro feature flag for FREE_SPACE_TREE (0x1)
BTRFS info (device loop0): clearing compat-ro feature flag for FREE_SPACE_TREE_VALID (0x2)
==================================================================
BUG: KASAN: slab-out-of-bounds in string_nocheck lib/vsprintf.c:646 [inline]
BUG: KASAN: slab-out-of-bounds in string+0x218/0x2b0 lib/vsprintf.c:728
Read of size 1 at addr ffff88807bb70a28 by task syz-executor.0/5482

CPU: 0 PID: 5482 Comm: syz-executor.0 Not tainted 6.7.0-rc5-syzkaller-00200-g3bd7d7488169-dirty #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 11/17/2023
Call Trace:
 <TASK>
 __dump_stack lib/dump_stack.c:88 [inline]
 dump_stack_lvl+0x1e7/0x2d0 lib/dump_stack.c:106
 print_address_description mm/kasan/report.c:364 [inline]
 print_report+0x163/0x540 mm/kasan/report.c:475
 kasan_report+0x142/0x170 mm/kasan/report.c:588
 string_nocheck lib/vsprintf.c:646 [inline]
 string+0x218/0x2b0 lib/vsprintf.c:728
 vsnprintf+0x1101/0x1da0 lib/vsprintf.c:2819
 vprintk_store+0x47f/0x1160 kernel/printk/printk.c:2187
 vprintk_emit+0x119/0x720 kernel/printk/printk.c:2284
 _printk+0xd5/0x120 kernel/printk/printk.c:2328
 btrfs_dev_replace_by_ioctl+0x16e/0x2020 fs/btrfs/dev-replace.c:744
 btrfs_ioctl_dev_replace+0x2c9/0x390 fs/btrfs/ioctl.c:3299
 vfs_ioctl fs/ioctl.c:51 [inline]
 __do_sys_ioctl fs/ioctl.c:871 [inline]
 __se_sys_ioctl+0xf8/0x170 fs/ioctl.c:857
 do_syscall_x64 arch/x86/entry/common.c:52 [inline]
 do_syscall_64+0x45/0x110 arch/x86/entry/common.c:83
 entry_SYSCALL_64_after_hwframe+0x63/0x6b
RIP: 0033:0x7f9e6107cba9
Code: 28 00 00 00 75 05 48 83 c4 28 c3 e8 e1 20 00 00 90 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 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:00007f9e61de30c8 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
RAX: ffffffffffffffda RBX: 00007f9e6119bf80 RCX: 00007f9e6107cba9
RDX: 0000000020000540 RSI: 00000000ca289435 RDI: 0000000000000005
RBP: 00007f9e610c847a R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 000000000000000b R14: 00007f9e6119bf80 R15: 00007fffc9000478
 </TASK>

Allocated by task 5482:
 kasan_save_stack mm/kasan/common.c:45 [inline]
 kasan_set_track+0x4f/0x70 mm/kasan/common.c:52
 ____kasan_kmalloc mm/kasan/common.c:374 [inline]
 __kasan_kmalloc+0x98/0xb0 mm/kasan/common.c:383
 kasan_kmalloc include/linux/kasan.h:198 [inline]
 __do_kmalloc_node mm/slab_common.c:1007 [inline]
 __kmalloc_node_track_caller+0xb1/0x190 mm/slab_common.c:1027
 memdup_user+0x2b/0xc0 mm/util.c:197
 btrfs_ioctl_dev_replace+0xb8/0x390 fs/btrfs/ioctl.c:3286
 vfs_ioctl fs/ioctl.c:51 [inline]
 __do_sys_ioctl fs/ioctl.c:871 [inline]
 __se_sys_ioctl+0xf8/0x170 fs/ioctl.c:857
 do_syscall_x64 arch/x86/entry/common.c:52 [inline]
 do_syscall_64+0x45/0x110 arch/x86/entry/common.c:83
 entry_SYSCALL_64_after_hwframe+0x63/0x6b

The buggy address belongs to the object at ffff88807bb70000
 which belongs to the cache kmalloc-4k of size 4096
The buggy address is located 0 bytes to the right of
 allocated 2600-byte region [ffff88807bb70000, ffff88807bb70a28)

The buggy address belongs to the physical page:
page:ffffea0001eedc00 refcount:1 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x7bb70
head:ffffea0001eedc00 order:3 entire_mapcount:0 nr_pages_mapped:0 pincount:0
flags: 0xfff00000000840(slab|head|node=0|zone=1|lastcpupid=0x7ff)
page_type: 0xffffffff()
raw: 00fff00000000840 ffff888012c42140 dead000000000122 0000000000000000
raw: 0000000000000000 0000000080040004 00000001ffffffff 0000000000000000
page dumped because: kasan: bad access detected
page_owner tracks the page as allocated
page last allocated via order 3, migratetype Unmovable, gfp_mask 0x1d20c0(__GFP_IO|__GFP_FS|__GFP_NOWARN|__GFP_NORETRY|__GFP_COMP|__GFP_NOMEMALLOC|__GFP_HARDWALL), pid 5482, tgid 5481 (syz-executor.0), ts 83591699256, free_ts 83563781743
 set_page_owner include/linux/page_owner.h:31 [inline]
 post_alloc_hook+0x1e6/0x210 mm/page_alloc.c:1537
 prep_new_page mm/page_alloc.c:1544 [inline]
 get_page_from_freelist+0x33ea/0x3570 mm/page_alloc.c:3312
 __alloc_pages+0x255/0x680 mm/page_alloc.c:4568
 alloc_pages_mpol+0x3de/0x640 mm/mempolicy.c:2133
 alloc_slab_page+0x6a/0x170 mm/slub.c:1870
 allocate_slab mm/slub.c:2017 [inline]
 new_slab+0x84/0x2f0 mm/slub.c:2070
 ___slab_alloc+0xc8a/0x1330 mm/slub.c:3223
 __slab_alloc mm/slub.c:3322 [inline]
 __slab_alloc_node mm/slub.c:3375 [inline]
 slab_alloc_node mm/slub.c:3468 [inline]
 __kmem_cache_alloc_node+0x21d/0x300 mm/slub.c:3517
 __do_kmalloc_node mm/slab_common.c:1006 [inline]
 __kmalloc_node_track_caller+0xa0/0x190 mm/slab_common.c:1027
 memdup_user+0x2b/0xc0 mm/util.c:197
 btrfs_ioctl_dev_replace+0xb8/0x390 fs/btrfs/ioctl.c:3286
 vfs_ioctl fs/ioctl.c:51 [inline]
 __do_sys_ioctl fs/ioctl.c:871 [inline]
 __se_sys_ioctl+0xf8/0x170 fs/ioctl.c:857
 do_syscall_x64 arch/x86/entry/common.c:52 [inline]
 do_syscall_64+0x45/0x110 arch/x86/entry/common.c:83
 entry_SYSCALL_64_after_hwframe+0x63/0x6b
page last free stack trace:
 reset_page_owner include/linux/page_owner.h:24 [inline]
 free_pages_prepare mm/page_alloc.c:1137 [inline]
 free_unref_page_prepare+0x931/0xa60 mm/page_alloc.c:2347
 free_unref_page+0x37/0x3f0 mm/page_alloc.c:2487
 discard_slab mm/slub.c:2116 [inline]
 __unfreeze_partials+0x1e0/0x220 mm/slub.c:2655
 put_cpu_partial+0x17b/0x250 mm/slub.c:2731
 __slab_free+0x2b6/0x390 mm/slub.c:3679
 qlink_free mm/kasan/quarantine.c:168 [inline]
 qlist_free_all+0x75/0xe0 mm/kasan/quarantine.c:187
 kasan_quarantine_reduce+0x14b/0x160 mm/kasan/quarantine.c:294
 __kasan_slab_alloc+0x23/0x70 mm/kasan/common.c:305
 kasan_slab_alloc include/linux/kasan.h:188 [inline]
 slab_post_alloc_hook+0x6c/0x3c0 mm/slab.h:763
 slab_alloc_node mm/slub.c:3478 [inline]
 slab_alloc mm/slub.c:3486 [inline]
 __kmem_cache_alloc_lru mm/slub.c:3493 [inline]
 kmem_cache_alloc+0x19e/0x2b0 mm/slub.c:3502
 anon_vma_chain_alloc mm/rmap.c:142 [inline]
 __anon_vma_prepare+0x68/0x410 mm/rmap.c:196
 vmf_anon_prepare mm/memory.c:3072 [inline]
 do_cow_fault mm/memory.c:4648 [inline]
 do_fault mm/memory.c:4765 [inline]
 do_pte_missing mm/memory.c:3731 [inline]
 handle_pte_fault mm/memory.c:5039 [inline]
 __handle_mm_fault mm/memory.c:5180 [inline]
 handle_mm_fault+0x5516/0x6680 mm/memory.c:5345
 do_user_addr_fault arch/x86/mm/fault.c:1413 [inline]
 handle_page_fault arch/x86/mm/fault.c:1505 [inline]
 exc_page_fault+0x2ad/0x870 arch/x86/mm/fault.c:1561
 asm_exc_page_fault+0x26/0x30 arch/x86/include/asm/idtentry.h:570

Memory state around the buggy address:
 ffff88807bb70900: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
 ffff88807bb70980: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
>ffff88807bb70a00: 00 00 00 00 00 fc fc fc fc fc fc fc fc fc fc fc
                                  ^
 ffff88807bb70a80: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
 ffff88807bb70b00: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
==================================================================


Tested on:

commit:         3bd7d748 Merge tag 'io_uring-6.7-2023-12-15' of git://..
git tree:       https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
console output: https://syzkaller.appspot.com/x/log.txt?x=104f2daee80000
kernel config:  https://syzkaller.appspot.com/x/.config?x=53ec3da1d259132f
dashboard link: https://syzkaller.appspot.com/bug?extid=33f23b49ac24f986c9e8
compiler:       Debian clang version 15.0.6, GNU ld (GNU Binutils for Debian) 2.40
patch:          https://syzkaller.appspot.com/x/patch.diff?x=148e8d01e80000