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Date: Mon, 18 Dec 2023 19:25:03 -0800
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Subject: Re: [syzbot] [btrfs?] KASAN: slab-out-of-bounds Read in
 getname_kernel (2)
From: syzbot <syzbot+33f23b49ac24f986c9e8@syzkaller.appspotmail.com>
To: eadavis@qq.com, linux-kernel@vger.kernel.org, 
	syzkaller-bugs@googlegroups.com
Content-Type: text/plain; charset="UTF-8"

Hello,

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

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 strlen+0x58/0x70 lib/string.c:418
Read of size 1 at addr ffff88814b62aa28 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
 strlen+0x58/0x70 lib/string.c:418
 getname_kernel+0x1d/0x2e0 fs/namei.c:226
 kern_path+0x1d/0x50 fs/namei.c:2609
 lookup_bdev block/bdev.c:979 [inline]
 bdev_open_by_path+0xd1/0x540 block/bdev.c:901
 btrfs_init_dev_replace_tgtdev fs/btrfs/dev-replace.c:260 [inline]
 btrfs_dev_replace_start fs/btrfs/dev-replace.c:638 [inline]
 btrfs_dev_replace_by_ioctl+0x41b/0x2010 fs/btrfs/dev-replace.c:748
 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: 0033:0x7f617807cba9
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:00007f6178dd40c8 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
RAX: ffffffffffffffda RBX: 00007f617819bf80 RCX: 00007f617807cba9
RDX: 0000000020000540 RSI: 00000000ca289435 RDI: 0000000000000005
RBP: 00007f61780c847a R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 000000000000000b R14: 00007f617819bf80 R15: 00007ffcbe283518
 </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 ffff88814b62a000
 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 [ffff88814b62a000, ffff88814b62aa28)

The buggy address belongs to the physical page:
page:ffffea00052d8a00 refcount:1 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x14b628
head:ffffea00052d8a00 order:3 entire_mapcount:0 nr_pages_mapped:0 pincount:0
flags: 0x57ff00000000840(slab|head|node=1|zone=2|lastcpupid=0x7ff)
page_type: 0xffffffff()
raw: 057ff00000000840 ffff888012c42140 dead000000000100 dead000000000122
raw: 0000000000000000 0000000000040004 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 0xd20c0(__GFP_IO|__GFP_FS|__GFP_NOWARN|__GFP_NORETRY|__GFP_COMP|__GFP_NOMEMALLOC), pid 1, tgid 1 (swapper/0), ts 12558368773, free_ts 0
 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
 kmalloc_reserve+0xf3/0x260 net/core/skbuff.c:582
 __alloc_skb+0x1b1/0x420 net/core/skbuff.c:651
 alloc_skb include/linux/skbuff.h:1286 [inline]
 nlmsg_new include/net/netlink.h:1010 [inline]
 ctrl_build_mcgrp_msg net/netlink/genetlink.c:1264 [inline]
 genl_ctrl_event+0x18e/0xc80 net/netlink/genetlink.c:1350
 genl_register_family+0x13df/0x17a0 net/netlink/genetlink.c:694
 handshake_init+0x2b/0xc0 net/handshake/netlink.c:255
 do_one_initcall+0x234/0x810 init/main.c:1236
 do_initcall_level+0x157/0x210 init/main.c:1298
page_owner free stack trace missing

Memory state around the buggy address:
 ffff88814b62a900: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
 ffff88814b62a980: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
>ffff88814b62aa00: 00 00 00 00 00 fc fc fc fc fc fc fc fc fc fc fc
                                  ^
 ffff88814b62aa80: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
 ffff88814b62ab00: 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=123685aee80000
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=131d1876e80000