Hello,
syzbot found the following issue on:
HEAD commit: 894d6f401b21 Merge tag 'spi-fix-v5.14-rc4' of git://git.ke..
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=17c622fa300000
kernel config: https://syzkaller.appspot.com/x/.config?x=343fd21f6f4da2d6
dashboard link: https://syzkaller.appspot.com/bug?extid=649e339fa6658ee623d3
compiler: gcc (Debian 10.2.1-6) 10.2.1 20210110, GNU ld (GNU Binutils for Debian) 2.35.1
syz repro: https://syzkaller.appspot.com/x/repro.syz?x=110319aa300000
C reproducer: https://syzkaller.appspot.com/x/repro.c?x=1142fac9d00000
IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: [email protected]
==================================================================
BUG: KASAN: use-after-free in instrument_atomic_read_write include/linux/instrumented.h:101 [inline]
BUG: KASAN: use-after-free in atomic_dec_and_test include/asm-generic/atomic-instrumented.h:542 [inline]
BUG: KASAN: use-after-free in nf_conntrack_put include/linux/netfilter/nf_conntrack_common.h:33 [inline]
BUG: KASAN: use-after-free in nf_ct_put include/net/netfilter/nf_conntrack.h:176 [inline]
BUG: KASAN: use-after-free in nft_ct_tmpl_put_pcpu+0x135/0x1e0 net/netfilter/nft_ct.c:356
Write of size 4 at addr ffff88803d750400 by task syz-executor409/9789
CPU: 0 PID: 9789 Comm: syz-executor409 Not tainted 5.14.0-rc4-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
Call Trace:
__dump_stack lib/dump_stack.c:88 [inline]
dump_stack_lvl+0xcd/0x134 lib/dump_stack.c:105
print_address_description.constprop.0.cold+0x6c/0x309 mm/kasan/report.c:233
__kasan_report mm/kasan/report.c:419 [inline]
kasan_report.cold+0x83/0xdf mm/kasan/report.c:436
check_region_inline mm/kasan/generic.c:183 [inline]
kasan_check_range+0x13d/0x180 mm/kasan/generic.c:189
instrument_atomic_read_write include/linux/instrumented.h:101 [inline]
atomic_dec_and_test include/asm-generic/atomic-instrumented.h:542 [inline]
nf_conntrack_put include/linux/netfilter/nf_conntrack_common.h:33 [inline]
nf_ct_put include/net/netfilter/nf_conntrack.h:176 [inline]
nft_ct_tmpl_put_pcpu+0x135/0x1e0 net/netfilter/nft_ct.c:356
__nft_ct_set_destroy net/netfilter/nft_ct.c:529 [inline]
__nft_ct_set_destroy net/netfilter/nft_ct.c:518 [inline]
nft_ct_set_init+0x41e/0x750 net/netfilter/nft_ct.c:614
nf_tables_newexpr net/netfilter/nf_tables_api.c:2742 [inline]
nft_expr_init+0x145/0x2d0 net/netfilter/nf_tables_api.c:2780
nft_set_elem_expr_alloc+0x27/0x280 net/netfilter/nf_tables_api.c:5284
nf_tables_newset+0x208a/0x32f0 net/netfilter/nf_tables_api.c:4389
nfnetlink_rcv_batch+0x1710/0x25f0 net/netfilter/nfnetlink.c:513
nfnetlink_rcv_skb_batch net/netfilter/nfnetlink.c:634 [inline]
nfnetlink_rcv+0x3af/0x420 net/netfilter/nfnetlink.c:652
netlink_unicast_kernel net/netlink/af_netlink.c:1314 [inline]
netlink_unicast+0x533/0x7d0 net/netlink/af_netlink.c:1340
netlink_sendmsg+0x86d/0xdb0 net/netlink/af_netlink.c:1929
sock_sendmsg_nosec net/socket.c:703 [inline]
sock_sendmsg+0xcf/0x120 net/socket.c:723
____sys_sendmsg+0x6e8/0x810 net/socket.c:2392
___sys_sendmsg+0xf3/0x170 net/socket.c:2446
__sys_sendmsg+0xe5/0x1b0 net/socket.c:2475
do_syscall_x64 arch/x86/entry/common.c:50 [inline]
do_syscall_64+0x35/0xb0 arch/x86/entry/common.c:80
entry_SYSCALL_64_after_hwframe+0x44/0xae
RIP: 0033:0x444819
Code: 28 00 00 00 75 05 48 83 c4 28 c3 e8 41 15 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 c4 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007fff0ba410d8 EFLAGS: 00000246 ORIG_RAX: 000000000000002e
RAX: ffffffffffffffda RBX: 0000000000000003 RCX: 0000000000444819
RDX: 0000000000000000 RSI: 00000000200000c0 RDI: 0000000000000003
RBP: 0000000000000000 R08: 00000000000f4240 R09: 00000000000f4240
R10: 00007fff0ba40b60 R11: 0000000000000246 R12: 00007fff0ba41100
R13: 00000000000f4240 R14: 000000000003754e R15: 00007fff0ba410f4
Allocated by task 9789:
kasan_save_stack+0x1b/0x40 mm/kasan/common.c:38
kasan_set_track mm/kasan/common.c:46 [inline]
set_alloc_info mm/kasan/common.c:434 [inline]
____kasan_kmalloc mm/kasan/common.c:513 [inline]
____kasan_kmalloc mm/kasan/common.c:472 [inline]
__kasan_kmalloc+0x9b/0xd0 mm/kasan/common.c:522
kmalloc include/linux/slab.h:591 [inline]
kzalloc include/linux/slab.h:721 [inline]
nf_ct_tmpl_alloc+0x8d/0x270 net/netfilter/nf_conntrack_core.c:569
nft_ct_tmpl_alloc_pcpu net/netfilter/nft_ct.c:371 [inline]
nft_ct_set_init+0x4d6/0x750 net/netfilter/nft_ct.c:567
nf_tables_newexpr net/netfilter/nf_tables_api.c:2742 [inline]
nft_expr_init+0x145/0x2d0 net/netfilter/nf_tables_api.c:2780
nft_set_elem_expr_alloc+0x27/0x280 net/netfilter/nf_tables_api.c:5284
nf_tables_newset+0x208a/0x32f0 net/netfilter/nf_tables_api.c:4389
nfnetlink_rcv_batch+0x1710/0x25f0 net/netfilter/nfnetlink.c:513
nfnetlink_rcv_skb_batch net/netfilter/nfnetlink.c:634 [inline]
nfnetlink_rcv+0x3af/0x420 net/netfilter/nfnetlink.c:652
netlink_unicast_kernel net/netlink/af_netlink.c:1314 [inline]
netlink_unicast+0x533/0x7d0 net/netlink/af_netlink.c:1340
netlink_sendmsg+0x86d/0xdb0 net/netlink/af_netlink.c:1929
sock_sendmsg_nosec net/socket.c:703 [inline]
sock_sendmsg+0xcf/0x120 net/socket.c:723
____sys_sendmsg+0x6e8/0x810 net/socket.c:2392
___sys_sendmsg+0xf3/0x170 net/socket.c:2446
__sys_sendmsg+0xe5/0x1b0 net/socket.c:2475
do_syscall_x64 arch/x86/entry/common.c:50 [inline]
do_syscall_64+0x35/0xb0 arch/x86/entry/common.c:80
entry_SYSCALL_64_after_hwframe+0x44/0xae
Freed by task 9788:
kasan_save_stack+0x1b/0x40 mm/kasan/common.c:38
kasan_set_track+0x1c/0x30 mm/kasan/common.c:46
kasan_set_free_info+0x20/0x30 mm/kasan/generic.c:360
____kasan_slab_free mm/kasan/common.c:366 [inline]
____kasan_slab_free mm/kasan/common.c:328 [inline]
__kasan_slab_free+0xfb/0x130 mm/kasan/common.c:374
kasan_slab_free include/linux/kasan.h:230 [inline]
slab_free_hook mm/slub.c:1625 [inline]
slab_free_freelist_hook+0xdf/0x240 mm/slub.c:1650
slab_free mm/slub.c:3210 [inline]
kfree+0xe4/0x530 mm/slub.c:4264
nf_ct_tmpl_free net/netfilter/nf_conntrack_core.c:590 [inline]
destroy_conntrack+0x222/0x2c0 net/netfilter/nf_conntrack_core.c:613
nf_conntrack_destroy+0xab/0x230 net/netfilter/core.c:677
nf_conntrack_put include/linux/netfilter/nf_conntrack_common.h:34 [inline]
nf_ct_put include/net/netfilter/nf_conntrack.h:176 [inline]
nft_ct_tmpl_put_pcpu+0x15e/0x1e0 net/netfilter/nft_ct.c:356
__nft_ct_set_destroy net/netfilter/nft_ct.c:529 [inline]
__nft_ct_set_destroy net/netfilter/nft_ct.c:518 [inline]
nft_ct_set_init+0x41e/0x750 net/netfilter/nft_ct.c:614
nf_tables_newexpr net/netfilter/nf_tables_api.c:2742 [inline]
nft_expr_init+0x145/0x2d0 net/netfilter/nf_tables_api.c:2780
nft_set_elem_expr_alloc+0x27/0x280 net/netfilter/nf_tables_api.c:5284
nf_tables_newset+0x208a/0x32f0 net/netfilter/nf_tables_api.c:4389
nfnetlink_rcv_batch+0x1710/0x25f0 net/netfilter/nfnetlink.c:513
nfnetlink_rcv_skb_batch net/netfilter/nfnetlink.c:634 [inline]
nfnetlink_rcv+0x3af/0x420 net/netfilter/nfnetlink.c:652
netlink_unicast_kernel net/netlink/af_netlink.c:1314 [inline]
netlink_unicast+0x533/0x7d0 net/netlink/af_netlink.c:1340
netlink_sendmsg+0x86d/0xdb0 net/netlink/af_netlink.c:1929
sock_sendmsg_nosec net/socket.c:703 [inline]
sock_sendmsg+0xcf/0x120 net/socket.c:723
____sys_sendmsg+0x6e8/0x810 net/socket.c:2392
___sys_sendmsg+0xf3/0x170 net/socket.c:2446
__sys_sendmsg+0xe5/0x1b0 net/socket.c:2475
do_syscall_x64 arch/x86/entry/common.c:50 [inline]
do_syscall_64+0x35/0xb0 arch/x86/entry/common.c:80
entry_SYSCALL_64_after_hwframe+0x44/0xae
The buggy address belongs to the object at ffff88803d750400
which belongs to the cache kmalloc-512 of size 512
The buggy address is located 0 bytes inside of
512-byte region [ffff88803d750400, ffff88803d750600)
The buggy address belongs to the page:
page:ffffea0000f5d400 refcount:1 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x3d750
head:ffffea0000f5d400 order:2 compound_mapcount:0 compound_pincount:0
flags: 0xfff00000010200(slab|head|node=0|zone=1|lastcpupid=0x7ff)
raw: 00fff00000010200 0000000000000000 dead000000000122 ffff888010841c80
raw: 0000000000000000 0000000080100010 00000001ffffffff 0000000000000000
page dumped because: kasan: bad access detected
page_owner tracks the page as allocated
page last allocated via order 2, migratetype Unmovable, gfp_mask 0xd20c0(__GFP_IO|__GFP_FS|__GFP_NOWARN|__GFP_NORETRY|__GFP_COMP|__GFP_NOMEMALLOC), pid 9789, ts 226704064982, free_ts 0
prep_new_page mm/page_alloc.c:2436 [inline]
get_page_from_freelist+0xa72/0x2f80 mm/page_alloc.c:4169
__alloc_pages+0x1b2/0x500 mm/page_alloc.c:5391
alloc_pages+0x18c/0x2a0 mm/mempolicy.c:2244
alloc_slab_page mm/slub.c:1688 [inline]
allocate_slab+0x32e/0x4b0 mm/slub.c:1828
new_slab mm/slub.c:1891 [inline]
new_slab_objects mm/slub.c:2637 [inline]
___slab_alloc+0x4ba/0x820 mm/slub.c:2800
__slab_alloc.constprop.0+0xa7/0xf0 mm/slub.c:2840
slab_alloc_node mm/slub.c:2922 [inline]
slab_alloc mm/slub.c:2964 [inline]
kmem_cache_alloc_trace+0x30f/0x3c0 mm/slub.c:2981
kmalloc include/linux/slab.h:591 [inline]
kzalloc include/linux/slab.h:721 [inline]
nf_ct_tmpl_alloc+0x8d/0x270 net/netfilter/nf_conntrack_core.c:569
nft_ct_tmpl_alloc_pcpu net/netfilter/nft_ct.c:371 [inline]
nft_ct_set_init+0x4d6/0x750 net/netfilter/nft_ct.c:567
nf_tables_newexpr net/netfilter/nf_tables_api.c:2742 [inline]
nft_expr_init+0x145/0x2d0 net/netfilter/nf_tables_api.c:2780
nft_set_elem_expr_alloc+0x27/0x280 net/netfilter/nf_tables_api.c:5284
nf_tables_newset+0x208a/0x32f0 net/netfilter/nf_tables_api.c:4389
nfnetlink_rcv_batch+0x1710/0x25f0 net/netfilter/nfnetlink.c:513
nfnetlink_rcv_skb_batch net/netfilter/nfnetlink.c:634 [inline]
nfnetlink_rcv+0x3af/0x420 net/netfilter/nfnetlink.c:652
netlink_unicast_kernel net/netlink/af_netlink.c:1314 [inline]
netlink_unicast+0x533/0x7d0 net/netlink/af_netlink.c:1340
netlink_sendmsg+0x86d/0xdb0 net/netlink/af_netlink.c:1929
page_owner free stack trace missing
Memory state around the buggy address:
ffff88803d750300: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
ffff88803d750380: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
>ffff88803d750400: fa fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
^
ffff88803d750480: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
ffff88803d750500: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
==================================================================
---
This report is generated by a bot. It may contain errors.
See https://goo.gl/tpsmEJ for more information about syzbot.
syzbot engineers can be reached at [email protected].
syzbot will keep track of this issue. See:
https://goo.gl/tpsmEJ#status for how to communicate with syzbot.
syzbot can test patches for this issue, for details see:
https://goo.gl/tpsmEJ#testing-patches
syzbot has bisected this issue to:
commit 65038428b2c6c5be79d3f78a6b79c0cdc3a58a41
Author: Pablo Neira Ayuso <[email protected]>
Date: Tue Mar 17 13:13:46 2020 +0000
netfilter: nf_tables: allow to specify stateful expression in set definition
bisection log: https://syzkaller.appspot.com/x/bisect.txt?x=1145a881300000
start commit: 894d6f401b21 Merge tag 'spi-fix-v5.14-rc4' of git://git.ke..
git tree: upstream
final oops: https://syzkaller.appspot.com/x/report.txt?x=1345a881300000
console output: https://syzkaller.appspot.com/x/log.txt?x=1545a881300000
kernel config: https://syzkaller.appspot.com/x/.config?x=343fd21f6f4da2d6
dashboard link: https://syzkaller.appspot.com/bug?extid=649e339fa6658ee623d3
syz repro: https://syzkaller.appspot.com/x/repro.syz?x=110319aa300000
C reproducer: https://syzkaller.appspot.com/x/repro.c?x=1142fac9d00000
Reported-by: [email protected]
Fixes: 65038428b2c6 ("netfilter: nf_tables: allow to specify stateful expression in set definition")
For information about bisection process see: https://goo.gl/tpsmEJ#bisection
On 8/7/21 4:44 PM, syzbot wrote:
> Hello,
>
> syzbot found the following issue on:
>
> HEAD commit: 894d6f401b21 Merge tag 'spi-fix-v5.14-rc4' of git://git.ke..
> git tree: upstream
> console output: https://syzkaller.appspot.com/x/log.txt?x=17c622fa300000
> kernel config: https://syzkaller.appspot.com/x/.config?x=343fd21f6f4da2d6
> dashboard link: https://syzkaller.appspot.com/bug?extid=649e339fa6658ee623d3
> compiler: gcc (Debian 10.2.1-6) 10.2.1 20210110, GNU ld (GNU Binutils for Debian) 2.35.1
> syz repro: https://syzkaller.appspot.com/x/repro.syz?x=110319aa300000
> C reproducer: https://syzkaller.appspot.com/x/repro.c?x=1142fac9d00000
>
> IMPORTANT: if you fix the issue, please add the following tag to the commit:
> Reported-by: [email protected]
>
> ==================================================================
> BUG: KASAN: use-after-free in instrument_atomic_read_write include/linux/instrumented.h:101 [inline]
> BUG: KASAN: use-after-free in atomic_dec_and_test include/asm-generic/atomic-instrumented.h:542 [inline]
> BUG: KASAN: use-after-free in nf_conntrack_put include/linux/netfilter/nf_conntrack_common.h:33 [inline]
> BUG: KASAN: use-after-free in nf_ct_put include/net/netfilter/nf_conntrack.h:176 [inline]
> BUG: KASAN: use-after-free in nft_ct_tmpl_put_pcpu+0x135/0x1e0 net/netfilter/nft_ct.c:356
> Write of size 4 at addr ffff88803d750400 by task syz-executor409/9789
>
> CPU: 0 PID: 9789 Comm: syz-executor409 Not tainted 5.14.0-rc4-syzkaller #0
> Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
> Call Trace:
> __dump_stack lib/dump_stack.c:88 [inline]
> dump_stack_lvl+0xcd/0x134 lib/dump_stack.c:105
> print_address_description.constprop.0.cold+0x6c/0x309 mm/kasan/report.c:233
> __kasan_report mm/kasan/report.c:419 [inline]
> kasan_report.cold+0x83/0xdf mm/kasan/report.c:436
> check_region_inline mm/kasan/generic.c:183 [inline]
> kasan_check_range+0x13d/0x180 mm/kasan/generic.c:189
> instrument_atomic_read_write include/linux/instrumented.h:101 [inline]
> atomic_dec_and_test include/asm-generic/atomic-instrumented.h:542 [inline]
> nf_conntrack_put include/linux/netfilter/nf_conntrack_common.h:33 [inline]
> nf_ct_put include/net/netfilter/nf_conntrack.h:176 [inline]
> nft_ct_tmpl_put_pcpu+0x135/0x1e0 net/netfilter/nft_ct.c:356
(*)
> __nft_ct_set_destroy net/netfilter/nft_ct.c:529 [inline]
> __nft_ct_set_destroy net/netfilter/nft_ct.c:518 [inline]
> nft_ct_set_init+0x41e/0x750 net/netfilter/nft_ct.c:614
> nf_tables_newexpr net/netfilter/nf_tables_api.c:2742 [inline]
> nft_expr_init+0x145/0x2d0 net/netfilter/nf_tables_api.c:2780
> nft_set_elem_expr_alloc+0x27/0x280 net/netfilter/nf_tables_api.c:5284
> nf_tables_newset+0x208a/0x32f0 net/netfilter/nf_tables_api.c:4389
> nfnetlink_rcv_batch+0x1710/0x25f0 net/netfilter/nfnetlink.c:513
> nfnetlink_rcv_skb_batch net/netfilter/nfnetlink.c:634 [inline]
> nfnetlink_rcv+0x3af/0x420 net/netfilter/nfnetlink.c:652
> netlink_unicast_kernel net/netlink/af_netlink.c:1314 [inline]
> netlink_unicast+0x533/0x7d0 net/netlink/af_netlink.c:1340
> netlink_sendmsg+0x86d/0xdb0 net/netlink/af_netlink.c:1929
> sock_sendmsg_nosec net/socket.c:703 [inline]
> sock_sendmsg+0xcf/0x120 net/socket.c:723
> ____sys_sendmsg+0x6e8/0x810 net/socket.c:2392
> ___sys_sendmsg+0xf3/0x170 net/socket.c:2446
> __sys_sendmsg+0xe5/0x1b0 net/socket.c:2475
> do_syscall_x64 arch/x86/entry/common.c:50 [inline]
> do_syscall_64+0x35/0xb0 arch/x86/entry/common.c:80
> entry_SYSCALL_64_after_hwframe+0x44/0xae
> RIP: 0033:0x444819
[snip]
> Freed by task 9788:
> kasan_save_stack+0x1b/0x40 mm/kasan/common.c:38
> kasan_set_track+0x1c/0x30 mm/kasan/common.c:46
> kasan_set_free_info+0x20/0x30 mm/kasan/generic.c:360
> ____kasan_slab_free mm/kasan/common.c:366 [inline]
> ____kasan_slab_free mm/kasan/common.c:328 [inline]
> __kasan_slab_free+0xfb/0x130 mm/kasan/common.c:374
> kasan_slab_free include/linux/kasan.h:230 [inline]
> slab_free_hook mm/slub.c:1625 [inline]
> slab_free_freelist_hook+0xdf/0x240 mm/slub.c:1650
> slab_free mm/slub.c:3210 [inline]
> kfree+0xe4/0x530 mm/slub.c:4264
> nf_ct_tmpl_free net/netfilter/nf_conntrack_core.c:590 [inline]
> destroy_conntrack+0x222/0x2c0 net/netfilter/nf_conntrack_core.c:613
> nf_conntrack_destroy+0xab/0x230 net/netfilter/core.c:677
> nf_conntrack_put include/linux/netfilter/nf_conntrack_common.h:34 [inline]
> nf_ct_put include/net/netfilter/nf_conntrack.h:176 [inline]
> nft_ct_tmpl_put_pcpu+0x15e/0x1e0 net/netfilter/nft_ct.c:356
I think, there a missing lock in this function:
for_each_possible_cpu(cpu) {
ct = per_cpu(nft_ct_pcpu_template, cpu);
if (!ct)
break;
nf_ct_put(ct);
per_cpu(nft_ct_pcpu_template, cpu) = NULL;
}
Syzbot hit a UAF in nft_ct_tmpl_put_pcpu() (*), but freed template
should be NULL.
So I suspect following scenario:
CPU0: CPU1:
= per_cpu()
= per_cpu()
nf_ct_put
per_cpu = NULL
nf_ct_put()
* UAF *
#syz test
git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git master
With regards,
Pavel Skripkin
> __nft_ct_set_destroy net/netfilter/nft_ct.c:529 [inline]
> __nft_ct_set_destroy net/netfilter/nft_ct.c:518 [inline]
> nft_ct_set_init+0x41e/0x750 net/netfilter/nft_ct.c:614
> nf_tables_newexpr net/netfilter/nf_tables_api.c:2742 [inline]
> nft_expr_init+0x145/0x2d0 net/netfilter/nf_tables_api.c:2780
> nft_set_elem_expr_alloc+0x27/0x280 net/netfilter/nf_tables_api.c:5284
> nf_tables_newset+0x208a/0x32f0 net/netfilter/nf_tables_api.c:4389
> nfnetlink_rcv_batch+0x1710/0x25f0 net/netfilter/nfnetlink.c:513
> nfnetlink_rcv_skb_batch net/netfilter/nfnetlink.c:634 [inline]
> nfnetlink_rcv+0x3af/0x420 net/netfilter/nfnetlink.c:652
> netlink_unicast_kernel net/netlink/af_netlink.c:1314 [inline]
> netlink_unicast+0x533/0x7d0 net/netlink/af_netlink.c:1340
> netlink_sendmsg+0x86d/0xdb0 net/netlink/af_netlink.c:1929
> sock_sendmsg_nosec net/socket.c:703 [inline]
> sock_sendmsg+0xcf/0x120 net/socket.c:723
> ____sys_sendmsg+0x6e8/0x810 net/socket.c:2392
> ___sys_sendmsg+0xf3/0x170 net/socket.c:2446
> __sys_sendmsg+0xe5/0x1b0 net/socket.c:2475
> do_syscall_x64 arch/x86/entry/common.c:50 [inline]
> do_syscall_64+0x35/0xb0 arch/x86/entry/common.c:80
> entry_SYSCALL_64_after_hwframe+0x44/0xae
>
> The buggy address belongs to the object at ffff88803d750400
> which belongs to the cache kmalloc-512 of size 512
> The buggy address is located 0 bytes inside of
> 512-byte region [ffff88803d750400, ffff88803d750600)
> The buggy address belongs to the page:
> page:ffffea0000f5d400 refcount:1 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x3d750
> head:ffffea0000f5d400 order:2 compound_mapcount:0 compound_pincount:0
> flags: 0xfff00000010200(slab|head|node=0|zone=1|lastcpupid=0x7ff)
> raw: 00fff00000010200 0000000000000000 dead000000000122 ffff888010841c80
> raw: 0000000000000000 0000000080100010 00000001ffffffff 0000000000000000
> page dumped because: kasan: bad access detected
> page_owner tracks the page as allocated
> page last allocated via order 2, migratetype Unmovable, gfp_mask 0xd20c0(__GFP_IO|__GFP_FS|__GFP_NOWARN|__GFP_NORETRY|__GFP_COMP|__GFP_NOMEMALLOC), pid 9789, ts 226704064982, free_ts 0
> prep_new_page mm/page_alloc.c:2436 [inline]
> get_page_from_freelist+0xa72/0x2f80 mm/page_alloc.c:4169
> __alloc_pages+0x1b2/0x500 mm/page_alloc.c:5391
> alloc_pages+0x18c/0x2a0 mm/mempolicy.c:2244
> alloc_slab_page mm/slub.c:1688 [inline]
> allocate_slab+0x32e/0x4b0 mm/slub.c:1828
> new_slab mm/slub.c:1891 [inline]
> new_slab_objects mm/slub.c:2637 [inline]
> ___slab_alloc+0x4ba/0x820 mm/slub.c:2800
> __slab_alloc.constprop.0+0xa7/0xf0 mm/slub.c:2840
> slab_alloc_node mm/slub.c:2922 [inline]
> slab_alloc mm/slub.c:2964 [inline]
> kmem_cache_alloc_trace+0x30f/0x3c0 mm/slub.c:2981
> kmalloc include/linux/slab.h:591 [inline]
> kzalloc include/linux/slab.h:721 [inline]
> nf_ct_tmpl_alloc+0x8d/0x270 net/netfilter/nf_conntrack_core.c:569
> nft_ct_tmpl_alloc_pcpu net/netfilter/nft_ct.c:371 [inline]
> nft_ct_set_init+0x4d6/0x750 net/netfilter/nft_ct.c:567
> nf_tables_newexpr net/netfilter/nf_tables_api.c:2742 [inline]
> nft_expr_init+0x145/0x2d0 net/netfilter/nf_tables_api.c:2780
> nft_set_elem_expr_alloc+0x27/0x280 net/netfilter/nf_tables_api.c:5284
> nf_tables_newset+0x208a/0x32f0 net/netfilter/nf_tables_api.c:4389
> nfnetlink_rcv_batch+0x1710/0x25f0 net/netfilter/nfnetlink.c:513
> nfnetlink_rcv_skb_batch net/netfilter/nfnetlink.c:634 [inline]
> nfnetlink_rcv+0x3af/0x420 net/netfilter/nfnetlink.c:652
> netlink_unicast_kernel net/netlink/af_netlink.c:1314 [inline]
> netlink_unicast+0x533/0x7d0 net/netlink/af_netlink.c:1340
> netlink_sendmsg+0x86d/0xdb0 net/netlink/af_netlink.c:1929
> page_owner free stack trace missing
>
> Memory state around the buggy address:
> ffff88803d750300: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
> ffff88803d750380: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
>>ffff88803d750400: fa fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
> ^
> ffff88803d750480: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
> ffff88803d750500: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
> ==================================================================
>
Pavel Skripkin <[email protected]> wrote:
> I think, there a missing lock in this function:
>
> for_each_possible_cpu(cpu) {
> ct = per_cpu(nft_ct_pcpu_template, cpu);
> if (!ct)
> break;
> nf_ct_put(ct);
> per_cpu(nft_ct_pcpu_template, cpu) = NULL;
>
> }
>
> Syzbot hit a UAF in nft_ct_tmpl_put_pcpu() (*), but freed template should be
> NULL.
>
> So I suspect following scenario:
>
>
> CPU0: CPU1:
> = per_cpu()
> = per_cpu()
>
> nf_ct_put
> per_cpu = NULL
> nf_ct_put()
> * UAF *
Yes and no. The above is fine since pcpu will return different pointers
for cpu 0 and 1.
The race is between two different net namespaces that race when
changing nft_ct_pcpu_template_refcnt.
This happens since
commit f102d66b335a417d4848da9441f585695a838934
netfilter: nf_tables: use dedicated mutex to guard transactions
Before this, all transactions were serialized by a global mutex,
now we only serialize transactions in the same netns.
Its probably best to add
DEFINE_MUTEX(nft_ct_pcpu_mutex) and then acquire that when we need to
inc/dec the nft_ct_pcpu_template_refcnt so we can't have two distinct
cpus hitting a zero refcount.
Would you send a patch for this?
Thanks.
On 8/9/21 11:39 PM, Florian Westphal wrote:
> Pavel Skripkin <[email protected]> wrote:
>> I think, there a missing lock in this function:
>>
>> for_each_possible_cpu(cpu) {
>> ct = per_cpu(nft_ct_pcpu_template, cpu);
(*)
>> if (!ct) >> break;
>> nf_ct_put(ct);
>> per_cpu(nft_ct_pcpu_template, cpu) = NULL;
>>
>> }
>>
>> Syzbot hit a UAF in nft_ct_tmpl_put_pcpu() (*), but freed template should be
>> NULL.
>>
>> So I suspect following scenario:
>>
>>
>> CPU0: CPU1:
>> = per_cpu()
>> = per_cpu()
>>
>> nf_ct_put
>> per_cpu = NULL
>> nf_ct_put()
>> * UAF *
Hi, Florian!
>
> Yes and no. The above is fine since pcpu will return different pointers
> for cpu 0 and 1.
>
Dumb question: why per_cpu() will return 2 different pointers for CPU 1
and CPU 0? As I understand for_each_possible_cpu() will iterate over all
CPUs which could ever be enabled. So, we can hit situation when 2
concurrent processes call per_cpu() with same cpu value (*).
> The race is between two different net namespaces that race when
> changing nft_ct_pcpu_template_refcnt.
> This happens since
>
> commit f102d66b335a417d4848da9441f585695a838934
> netfilter: nf_tables: use dedicated mutex to guard transactions
>
> Before this, all transactions were serialized by a global mutex,
> now we only serialize transactions in the same netns.
>
> Its probably best to add
> DEFINE_MUTEX(nft_ct_pcpu_mutex) and then acquire that when we need to
> inc/dec the nft_ct_pcpu_template_refcnt so we can't have two distinct
> cpus hitting a zero refcount.
>
> Would you send a patch for this?
>
Anyway, I think, moving locking a bit higher is good here, let's test
it. I will prepare a patch, if it will pass syzbot testing, thanks!
#syz test
git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git master
With regards,
Pavel Skripkin
Pavel Skripkin <[email protected]> wrote:
> Dumb question: why per_cpu() will return 2 different pointers for CPU 1 and
> CPU 0? As I understand for_each_possible_cpu() will iterate over all
> CPUs which could ever be enabled. So, we can hit situation when 2 concurrent
> processes call per_cpu() with same cpu value (*).
Yes, that is what I was trying to say, the race is that we can have > 1
processes here ever since the global transaction mutex was removed in 2018.
> Anyway, I think, moving locking a bit higher is good here, let's test it. I
> will prepare a patch, if it will pass syzbot testing, thanks!
It looks correct to me, thanks.
Hello,
syzbot has tested the proposed patch and the reproducer did not trigger any issue:
Reported-and-tested-by: [email protected]
Tested on:
commit: 9a73fa37 Merge branch 'for-5.14-fixes' of git://git.ke..
git tree: upstream
kernel config: https://syzkaller.appspot.com/x/.config?x=e3a20bae04b96ccd
dashboard link: https://syzkaller.appspot.com/bug?extid=649e339fa6658ee623d3
compiler: gcc (Debian 10.2.1-6) 10.2.1 20210110, GNU ld (GNU Binutils for Debian) 2.35.1
patch: https://syzkaller.appspot.com/x/patch.diff?x=153511fa300000
Note: testing is done by a robot and is best-effort only.
Hello,
syzbot has tested the proposed patch and the reproducer did not trigger any issue:
Reported-and-tested-by: [email protected]
Tested on:
commit: 9a73fa37 Merge branch 'for-5.14-fixes' of git://git.ke..
git tree: upstream
kernel config: https://syzkaller.appspot.com/x/.config?x=e3a20bae04b96ccd
dashboard link: https://syzkaller.appspot.com/bug?extid=649e339fa6658ee623d3
compiler: gcc (Debian 10.2.1-6) 10.2.1 20210110, GNU ld (GNU Binutils for Debian) 2.35.1
patch: https://syzkaller.appspot.com/x/patch.diff?x=12d6baf6300000
Note: testing is done by a robot and is best-effort only.