[syzbot] [bpf?] [net?] KASAN: slab-use-after-free Read in nla_find

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: 358105ab92fc Merge branch 'tcp-dccp-refine-source-port-sel..
git tree: net-next
console+strace: https://syzkaller.appspot.com/x/log.txt?x=10b28c06e80000
kernel config: https://syzkaller.appspot.com/x/.config?x=df5e944701db1d04
dashboard link: https://syzkaller.appspot.com/bug?extid=f43a23b6e622797c7a28
compiler: gcc (Debian 12.2.0-14) 12.2.0, GNU ld (GNU Binutils for Debian) 2.40
syz repro: https://syzkaller.appspot.com/x/repro.syz?x=13250e06e80000
C reproducer: https://syzkaller.appspot.com/x/repro.c?x=16331cd1e80000

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/72500aefe96d/disk-358105ab.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/e4eb60a8a727/vmlinux-358105ab.xz
kernel image: https://storage.googleapis.com/syzbot-assets/6a645dff90bd/bzImage-358105ab.xz

The issue was bisected to:

commit 172db56d90d29e47e7d0d64885d5dbd92c87ec42
Author: Kees Cook <kees...@chromium.org>
Date: Wed Dec 6 20:59:07 2023 +0000

netlink: Return unsigned value for nla_len()

bisection log: https://syzkaller.appspot.com/x/bisect.txt?x=134506c6e80000
final oops: https://syzkaller.appspot.com/x/report.txt?x=10c506c6e80000
console output: https://syzkaller.appspot.com/x/log.txt?x=174506c6e80000

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+f43a23...@syzkaller.appspotmail.com
Fixes: 172db56d90d2 ("netlink: Return unsigned value for nla_len()")

==================================================================
BUG: KASAN: slab-use-after-free in nla_ok include/net/netlink.h:1230 [inline]
BUG: KASAN: slab-use-after-free in nla_find+0x120/0x130 lib/nlattr.c:746
Read of size 2 at addr ffff88807bc42ca0 by task syz-executor426/5060

CPU: 1 PID: 5060 Comm: syz-executor426 Not tainted 6.7.0-rc5-syzkaller-01062-g358105ab92fc #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+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
nla_ok include/net/netlink.h:1230 [inline]
nla_find+0x120/0x130 lib/nlattr.c:746
nla_find_nested include/net/netlink.h:1260 [inline]
____bpf_skb_get_nlattr_nest net/core/filter.c:209 [inline]
bpf_skb_get_nlattr_nest+0x178/0x1f0 net/core/filter.c:192
</TASK>

Allocated by task 4521:
kasan_save_stack+0x33/0x50 mm/kasan/common.c:45
kasan_set_track+0x25/0x30 mm/kasan/common.c:52
____kasan_kmalloc mm/kasan/common.c:374 [inline]
__kasan_kmalloc+0xa2/0xb0 mm/kasan/common.c:383
kasan_kmalloc include/linux/kasan.h:198 [inline]
__do_kmalloc_node mm/slab_common.c:1007 [inline]
__kmalloc_node+0x5c/0x90 mm/slab_common.c:1014
kmalloc_node include/linux/slab.h:620 [inline]
kvmalloc_node+0x99/0x1a0 mm/util.c:617
kvmalloc include/linux/slab.h:738 [inline]
seq_buf_alloc fs/seq_file.c:38 [inline]
seq_read_iter+0x80b/0x1280 fs/seq_file.c:210
kernfs_fop_read_iter+0x410/0x580 fs/kernfs/file.c:279
call_read_iter include/linux/fs.h:2014 [inline]
new_sync_read fs/read_write.c:389 [inline]
vfs_read+0x4d4/0x8f0 fs/read_write.c:470
ksys_read+0x12f/0x250 fs/read_write.c:613
do_syscall_x64 arch/x86/entry/common.c:52 [inline]
do_syscall_64+0x40/0x110 arch/x86/entry/common.c:83
entry_SYSCALL_64_after_hwframe+0x63/0x6b

The buggy address belongs to the object at ffff88807bc42000
which belongs to the cache kmalloc-cg-4k of size 4096
The buggy address is located 3232 bytes inside of
freed 4096-byte region [ffff88807bc42000, ffff88807bc43000)

The buggy address belongs to the physical page:
page:ffffea0001ef1000 refcount:1 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x7bc40
head:ffffea0001ef1000 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 ffff88801304f500 ffffea0001dc3000 dead000000000002
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 0xd20c0(__GFP_IO|__GFP_FS|__GFP_NOWARN|__GFP_NORETRY|__GFP_COMP|__GFP_NOMEMALLOC), pid 4525, tgid 4525 (udevd), ts 40899198633, free_ts 40892363839
set_page_owner include/linux/page_owner.h:31 [inline]
post_alloc_hook+0x2d0/0x350 mm/page_alloc.c:1544
prep_new_page mm/page_alloc.c:1551 [inline]
get_page_from_freelist+0xa28/0x3730 mm/page_alloc.c:3319
__alloc_pages+0x22e/0x2420 mm/page_alloc.c:4575
alloc_pages_mpol+0x258/0x5f0 mm/mempolicy.c:2133
alloc_slab_page mm/slub.c:1870 [inline]
allocate_slab mm/slub.c:2017 [inline]
new_slab+0x283/0x3c0 mm/slub.c:2070
___slab_alloc+0x979/0x1500 mm/slub.c:3223
__slab_alloc.constprop.0+0x56/0xa0 mm/slub.c:3322
__slab_alloc_node mm/slub.c:3375 [inline]
slab_alloc_node mm/slub.c:3468 [inline]
__kmem_cache_alloc_node+0x131/0x310 mm/slub.c:3517
__do_kmalloc_node mm/slab_common.c:1006 [inline]
__kmalloc_node+0x4c/0x90 mm/slab_common.c:1014
kmalloc_node include/linux/slab.h:620 [inline]
kvmalloc_node+0x99/0x1a0 mm/util.c:617
kvmalloc include/linux/slab.h:738 [inline]
seq_buf_alloc fs/seq_file.c:38 [inline]
seq_read_iter+0x80b/0x1280 fs/seq_file.c:210
kernfs_fop_read_iter+0x410/0x580 fs/kernfs/file.c:279
call_read_iter include/linux/fs.h:2014 [inline]
new_sync_read fs/read_write.c:389 [inline]
vfs_read+0x4d4/0x8f0 fs/read_write.c:470
ksys_read+0x12f/0x250 fs/read_write.c:613
do_syscall_x64 arch/x86/entry/common.c:52 [inline]
do_syscall_64+0x40/0x110 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:1144 [inline]
free_unref_page_prepare+0x53c/0xb80 mm/page_alloc.c:2354
free_unref_page+0x33/0x3b0 mm/page_alloc.c:2494
qlink_free mm/kasan/quarantine.c:168 [inline]
qlist_free_all+0x6a/0x170 mm/kasan/quarantine.c:187
kasan_quarantine_reduce+0x18e/0x1d0 mm/kasan/quarantine.c:294
__kasan_slab_alloc+0x65/0x90 mm/kasan/common.c:305
kasan_slab_alloc include/linux/kasan.h:188 [inline]
slab_post_alloc_hook mm/slab.h:763 [inline]
slab_alloc_node mm/slub.c:3478 [inline]
__kmem_cache_alloc_node+0x195/0x310 mm/slub.c:3517
__do_kmalloc_node mm/slab_common.c:1006 [inline]
__kmalloc_node+0x4c/0x90 mm/slab_common.c:1014
kmalloc_node include/linux/slab.h:620 [inline]
kvmalloc_node+0x99/0x1a0 mm/util.c:617
kvmalloc include/linux/slab.h:738 [inline]
seq_buf_alloc fs/seq_file.c:38 [inline]
seq_read_iter+0x80b/0x1280 fs/seq_file.c:210
kernfs_fop_read_iter+0x410/0x580 fs/kernfs/file.c:279
call_read_iter include/linux/fs.h:2014 [inline]
new_sync_read fs/read_write.c:389 [inline]
vfs_read+0x4d4/0x8f0 fs/read_write.c:470
ksys_read+0x12f/0x250 fs/read_write.c:613
do_syscall_x64 arch/x86/entry/common.c:52 [inline]
do_syscall_64+0x40/0x110 arch/x86/entry/common.c:83
entry_SYSCALL_64_after_hwframe+0x63/0x6b

Memory state around the buggy address:
ffff88807bc42b80: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
ffff88807bc42c00: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>ffff88807bc42c80: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
^
ffff88807bc42d00: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
ffff88807bc42d80: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
==================================================================


---
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[Jakub Kicinski]

On Mon, 18 Dec 2023 06:43:26 -0800 syzbot wrote:
> __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
> nla_ok include/net/netlink.h:1230 [inline]
> nla_find+0x120/0x130 lib/nlattr.c:746
> nla_find_nested include/net/netlink.h:1260 [inline]
> ____bpf_skb_get_nlattr_nest net/core/filter.c:209 [inline]

This needs nla_ok() instead of playing with nla_len directly.
Will send a fix soon..