[PATCH 5.10 103/106] ipv6: avoid use-after-free in ip6_fragment()

Greg Kroah-Hartman
2022-12-12T13:19:18Z

From: Eric Dumazet <edumazet@google.com>

[ Upstream commit 803e84867de59a1e5d126666d25eb4860cfd2ebe ]

Blamed commit claimed rcu_read_lock() was held by ip6_fragment() callers.

It seems to not be always true, at least for UDP stack.

syzbot reported:

BUG: KASAN: use-after-free in ip6_dst_idev include/net/ip6_fib.h:245 [inline]
BUG: KASAN: use-after-free in ip6_fragment+0x2724/0x2770 net/ipv6/ip6_output.c:951
Read of size 8 at addr ffff88801d403e80 by task syz-executor.3/7618

CPU: 1 PID: 7618 Comm: syz-executor.3 Not tainted 6.1.0-rc6-syzkaller-00012-g4312098baf37 #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/26/2022
Call Trace:
<TASK>
__dump_stack lib/dump_stack.c:88 [inline]
dump_stack_lvl+0xd1/0x138 lib/dump_stack.c:106
print_address_description mm/kasan/report.c:284 [inline]
print_report+0x15e/0x45d mm/kasan/report.c:395
kasan_report+0xbf/0x1f0 mm/kasan/report.c:495
ip6_dst_idev include/net/ip6_fib.h:245 [inline]
ip6_fragment+0x2724/0x2770 net/ipv6/ip6_output.c:951
__ip6_finish_output net/ipv6/ip6_output.c:193 [inline]
ip6_finish_output+0x9a3/0x1170 net/ipv6/ip6_output.c:206
NF_HOOK_COND include/linux/netfilter.h:291 [inline]
ip6_output+0x1f1/0x540 net/ipv6/ip6_output.c:227
dst_output include/net/dst.h:445 [inline]
ip6_local_out+0xb3/0x1a0 net/ipv6/output_core.c:161
ip6_send_skb+0xbb/0x340 net/ipv6/ip6_output.c:1966
udp_v6_send_skb+0x82a/0x18a0 net/ipv6/udp.c:1286
udp_v6_push_pending_frames+0x140/0x200 net/ipv6/udp.c:1313
udpv6_sendmsg+0x18da/0x2c80 net/ipv6/udp.c:1606
inet6_sendmsg+0x9d/0xe0 net/ipv6/af_inet6.c:665
sock_sendmsg_nosec net/socket.c:714 [inline]
sock_sendmsg+0xd3/0x120 net/socket.c:734
sock_write_iter+0x295/0x3d0 net/socket.c:1108
call_write_iter include/linux/fs.h:2191 [inline]
new_sync_write fs/read_write.c:491 [inline]
vfs_write+0x9ed/0xdd0 fs/read_write.c:584
ksys_write+0x1ec/0x250 fs/read_write.c:637
do_syscall_x64 arch/x86/entry/common.c:50 [inline]
do_syscall_64+0x39/0xb0 arch/x86/entry/common.c:80
entry_SYSCALL_64_after_hwframe+0x63/0xcd
RIP: 0033:0x7fde3588c0d9
Code: 28 00 00 00 75 05 48 83 c4 28 c3 e8 f1 19 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 b8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007fde365b6168 EFLAGS: 00000246 ORIG_RAX: 0000000000000001
RAX: ffffffffffffffda RBX: 00007fde359ac050 RCX: 00007fde3588c0d9
RDX: 000000000000ffdc RSI: 00000000200000c0 RDI: 000000000000000a
RBP: 00007fde358e7ae9 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007fde35acfb1f R14: 00007fde365b6300 R15: 0000000000022000
</TASK>

Allocated by task 7618:
kasan_save_stack+0x22/0x40 mm/kasan/common.c:45
kasan_set_track+0x25/0x30 mm/kasan/common.c:52
__kasan_slab_alloc+0x82/0x90 mm/kasan/common.c:325
kasan_slab_alloc include/linux/kasan.h:201 [inline]
slab_post_alloc_hook mm/slab.h:737 [inline]
slab_alloc_node mm/slub.c:3398 [inline]
slab_alloc mm/slub.c:3406 [inline]
__kmem_cache_alloc_lru mm/slub.c:3413 [inline]
kmem_cache_alloc+0x2b4/0x3d0 mm/slub.c:3422
dst_alloc+0x14a/0x1f0 net/core/dst.c:92
ip6_dst_alloc+0x32/0xa0 net/ipv6/route.c:344
ip6_rt_pcpu_alloc net/ipv6/route.c:1369 [inline]
rt6_make_pcpu_route net/ipv6/route.c:1417 [inline]
ip6_pol_route+0x901/0x1190 net/ipv6/route.c:2254
pol_lookup_func include/net/ip6_fib.h:582 [inline]
fib6_rule_lookup+0x52e/0x6f0 net/ipv6/fib6_rules.c:121
ip6_route_output_flags_noref+0x2e6/0x380 net/ipv6/route.c:2625
ip6_route_output_flags+0x76/0x320 net/ipv6/route.c:2638
ip6_route_output include/net/ip6_route.h:98 [inline]
ip6_dst_lookup_tail+0x5ab/0x1620 net/ipv6/ip6_output.c:1092
ip6_dst_lookup_flow+0x90/0x1d0 net/ipv6/ip6_output.c:1222
ip6_sk_dst_lookup_flow+0x553/0x980 net/ipv6/ip6_output.c:1260
udpv6_sendmsg+0x151d/0x2c80 net/ipv6/udp.c:1554
inet6_sendmsg+0x9d/0xe0 net/ipv6/af_inet6.c:665
sock_sendmsg_nosec net/socket.c:714 [inline]
sock_sendmsg+0xd3/0x120 net/socket.c:734
__sys_sendto+0x23a/0x340 net/socket.c:2117
__do_sys_sendto net/socket.c:2129 [inline]
__se_sys_sendto net/socket.c:2125 [inline]
__x64_sys_sendto+0xe1/0x1b0 net/socket.c:2125
do_syscall_x64 arch/x86/entry/common.c:50 [inline]
do_syscall_64+0x39/0xb0 arch/x86/entry/common.c:80
entry_SYSCALL_64_after_hwframe+0x63/0xcd

Freed by task 7599:
kasan_save_stack+0x22/0x40 mm/kasan/common.c:45
kasan_set_track+0x25/0x30 mm/kasan/common.c:52
kasan_save_free_info+0x2e/0x40 mm/kasan/generic.c:511
____kasan_slab_free mm/kasan/common.c:236 [inline]
____kasan_slab_free+0x160/0x1c0 mm/kasan/common.c:200
kasan_slab_free include/linux/kasan.h:177 [inline]
slab_free_hook mm/slub.c:1724 [inline]
slab_free_freelist_hook+0x8b/0x1c0 mm/slub.c:1750
slab_free mm/slub.c:3661 [inline]
kmem_cache_free+0xee/0x5c0 mm/slub.c:3683
dst_destroy+0x2ea/0x400 net/core/dst.c:127
rcu_do_batch kernel/rcu/tree.c:2250 [inline]
rcu_core+0x81f/0x1980 kernel/rcu/tree.c:2510
__do_softirq+0x1fb/0xadc kernel/softirq.c:571

Last potentially related work creation:
kasan_save_stack+0x22/0x40 mm/kasan/common.c:45
__kasan_record_aux_stack+0xbc/0xd0 mm/kasan/generic.c:481
call_rcu+0x9d/0x820 kernel/rcu/tree.c:2798
dst_release net/core/dst.c:177 [inline]
dst_release+0x7d/0xe0 net/core/dst.c:167
refdst_drop include/net/dst.h:256 [inline]
skb_dst_drop include/net/dst.h:268 [inline]
skb_release_head_state+0x250/0x2a0 net/core/skbuff.c:838
skb_release_all net/core/skbuff.c:852 [inline]
__kfree_skb net/core/skbuff.c:868 [inline]
kfree_skb_reason+0x151/0x4b0 net/core/skbuff.c:891
kfree_skb_list_reason+0x4b/0x70 net/core/skbuff.c:901
kfree_skb_list include/linux/skbuff.h:1227 [inline]
ip6_fragment+0x2026/0x2770 net/ipv6/ip6_output.c:949
__ip6_finish_output net/ipv6/ip6_output.c:193 [inline]
ip6_finish_output+0x9a3/0x1170 net/ipv6/ip6_output.c:206
NF_HOOK_COND include/linux/netfilter.h:291 [inline]
ip6_output+0x1f1/0x540 net/ipv6/ip6_output.c:227
dst_output include/net/dst.h:445 [inline]
ip6_local_out+0xb3/0x1a0 net/ipv6/output_core.c:161
ip6_send_skb+0xbb/0x340 net/ipv6/ip6_output.c:1966
udp_v6_send_skb+0x82a/0x18a0 net/ipv6/udp.c:1286
udp_v6_push_pending_frames+0x140/0x200 net/ipv6/udp.c:1313
udpv6_sendmsg+0x18da/0x2c80 net/ipv6/udp.c:1606
inet6_sendmsg+0x9d/0xe0 net/ipv6/af_inet6.c:665
sock_sendmsg_nosec net/socket.c:714 [inline]
sock_sendmsg+0xd3/0x120 net/socket.c:734
sock_write_iter+0x295/0x3d0 net/socket.c:1108
call_write_iter include/linux/fs.h:2191 [inline]
new_sync_write fs/read_write.c:491 [inline]
vfs_write+0x9ed/0xdd0 fs/read_write.c:584
ksys_write+0x1ec/0x250 fs/read_write.c:637
do_syscall_x64 arch/x86/entry/common.c:50 [inline]
do_syscall_64+0x39/0xb0 arch/x86/entry/common.c:80
entry_SYSCALL_64_after_hwframe+0x63/0xcd

Second to last potentially related work creation:
kasan_save_stack+0x22/0x40 mm/kasan/common.c:45
__kasan_record_aux_stack+0xbc/0xd0 mm/kasan/generic.c:481
call_rcu+0x9d/0x820 kernel/rcu/tree.c:2798
dst_release net/core/dst.c:177 [inline]
dst_release+0x7d/0xe0 net/core/dst.c:167
refdst_drop include/net/dst.h:256 [inline]
skb_dst_drop include/net/dst.h:268 [inline]
__dev_queue_xmit+0x1b9d/0x3ba0 net/core/dev.c:4211
dev_queue_xmit include/linux/netdevice.h:3008 [inline]
neigh_resolve_output net/core/neighbour.c:1552 [inline]
neigh_resolve_output+0x51b/0x840 net/core/neighbour.c:1532
neigh_output include/net/neighbour.h:546 [inline]
ip6_finish_output2+0x56c/0x1530 net/ipv6/ip6_output.c:134
__ip6_finish_output net/ipv6/ip6_output.c:195 [inline]
ip6_finish_output+0x694/0x1170 net/ipv6/ip6_output.c:206
NF_HOOK_COND include/linux/netfilter.h:291 [inline]
ip6_output+0x1f1/0x540 net/ipv6/ip6_output.c:227
dst_output include/net/dst.h:445 [inline]
NF_HOOK include/linux/netfilter.h:302 [inline]
NF_HOOK include/linux/netfilter.h:296 [inline]
mld_sendpack+0xa09/0xe70 net/ipv6/mcast.c:1820
mld_send_cr net/ipv6/mcast.c:2121 [inline]
mld_ifc_work+0x720/0xdc0 net/ipv6/mcast.c:2653
process_one_work+0x9bf/0x1710 kernel/workqueue.c:2289
worker_thread+0x669/0x1090 kernel/workqueue.c:2436
kthread+0x2e8/0x3a0 kernel/kthread.c:376
ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:306

The buggy address belongs to the object at ffff88801d403dc0
which belongs to the cache ip6_dst_cache of size 240
The buggy address is located 192 bytes inside of
240-byte region [ffff88801d403dc0, ffff88801d403eb0)

The buggy address belongs to the physical page:
page:ffffea00007500c0 refcount:1 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x1d403
memcg:ffff888022f49c81
flags: 0xfff00000000200(slab|node=0|zone=1|lastcpupid=0x7ff)
raw: 00fff00000000200 ffffea0001ef6580 dead000000000002 ffff88814addf640
raw: 0000000000000000 00000000800c000c 00000001ffffffff ffff888022f49c81
page dumped because: kasan: bad access detected
page_owner tracks the page as allocated
page last allocated via order 0, migratetype Unmovable, gfp_mask 0x112a20(GFP_ATOMIC|__GFP_NOWARN|__GFP_NORETRY|__GFP_HARDWALL), pid 3719, tgid 3719 (kworker/0:6), ts 136223432244, free_ts 136222971441
prep_new_page mm/page_alloc.c:2539 [inline]
get_page_from_freelist+0x10b5/0x2d50 mm/page_alloc.c:4288
__alloc_pages+0x1cb/0x5b0 mm/page_alloc.c:5555
alloc_pages+0x1aa/0x270 mm/mempolicy.c:2285
alloc_slab_page mm/slub.c:1794 [inline]
allocate_slab+0x213/0x300 mm/slub.c:1939
new_slab mm/slub.c:1992 [inline]
___slab_alloc+0xa91/0x1400 mm/slub.c:3180
__slab_alloc.constprop.0+0x56/0xa0 mm/slub.c:3279
slab_alloc_node mm/slub.c:3364 [inline]
slab_alloc mm/slub.c:3406 [inline]
__kmem_cache_alloc_lru mm/slub.c:3413 [inline]
kmem_cache_alloc+0x31a/0x3d0 mm/slub.c:3422
dst_alloc+0x14a/0x1f0 net/core/dst.c:92
ip6_dst_alloc+0x32/0xa0 net/ipv6/route.c:344
icmp6_dst_alloc+0x71/0x680 net/ipv6/route.c:3261
mld_sendpack+0x5de/0xe70 net/ipv6/mcast.c:1809
mld_send_cr net/ipv6/mcast.c:2121 [inline]
mld_ifc_work+0x720/0xdc0 net/ipv6/mcast.c:2653
process_one_work+0x9bf/0x1710 kernel/workqueue.c:2289
worker_thread+0x669/0x1090 kernel/workqueue.c:2436
kthread+0x2e8/0x3a0 kernel/kthread.c:376
ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:306
page last free stack trace:
reset_page_owner include/linux/page_owner.h:24 [inline]
free_pages_prepare mm/page_alloc.c:1459 [inline]
free_pcp_prepare+0x65c/0xd90 mm/page_alloc.c:1509
free_unref_page_prepare mm/page_alloc.c:3387 [inline]
free_unref_page+0x1d/0x4d0 mm/page_alloc.c:3483
__unfreeze_partials+0x17c/0x1a0 mm/slub.c:2586
qlink_free mm/kasan/quarantine.c:168 [inline]
qlist_free_all+0x6a/0x170 mm/kasan/quarantine.c:187
kasan_quarantine_reduce+0x184/0x210 mm/kasan/quarantine.c:294
__kasan_slab_alloc+0x66/0x90 mm/kasan/common.c:302
kasan_slab_alloc include/linux/kasan.h:201 [inline]
slab_post_alloc_hook mm/slab.h:737 [inline]
slab_alloc_node mm/slub.c:3398 [inline]
kmem_cache_alloc_node+0x304/0x410 mm/slub.c:3443
__alloc_skb+0x214/0x300 net/core/skbuff.c:497
alloc_skb include/linux/skbuff.h:1267 [inline]
netlink_alloc_large_skb net/netlink/af_netlink.c:1191 [inline]
netlink_sendmsg+0x9a6/0xe10 net/netlink/af_netlink.c:1896
sock_sendmsg_nosec net/socket.c:714 [inline]
sock_sendmsg+0xd3/0x120 net/socket.c:734
__sys_sendto+0x23a/0x340 net/socket.c:2117
__do_sys_sendto net/socket.c:2129 [inline]
__se_sys_sendto net/socket.c:2125 [inline]
__x64_sys_sendto+0xe1/0x1b0 net/socket.c:2125
do_syscall_x64 arch/x86/entry/common.c:50 [inline]
do_syscall_64+0x39/0xb0 arch/x86/entry/common.c:80
entry_SYSCALL_64_after_hwframe+0x63/0xcd

Fixes: 1758fd4688eb ("ipv6: remove unnecessary dst_hold() in ip6_fragment()")
Reported-by: syzbot+8c0ac31aa9681abb9e2d@syzkaller.appspotmail.com
Signed-off-by: Eric Dumazet <edumazet@google.com>
Cc: Wei Wang <weiwan@google.com>
Cc: Martin KaFai Lau <kafai@fb.com>
Link: https://lore.kernel.org/r/20221206101351.2037285-1-edumazet@google.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
net/ipv6/ip6_output.c | 5 +++++
1 file changed, 5 insertions(+)

diff --git a/net/ipv6/ip6_output.c b/net/ipv6/ip6_output.c
index fadad8e83521..e427f5040a08 100644
--- a/net/ipv6/ip6_output.c
+++ b/net/ipv6/ip6_output.c
@@ -919,6 +919,9 @@ int ip6_fragment(struct net *net, struct sock *sk, struct sk_buff *skb,
if (err < 0)
goto fail;

+ /* We prevent @rt from being freed. */
+ rcu_read_lock();
+
for (;;) {
/* Prepare header of the next frame,
* before previous one went down. */
@@ -942,6 +945,7 @@ int ip6_fragment(struct net *net, struct sock *sk, struct sk_buff *skb,
if (err == 0) {
IP6_INC_STATS(net, ip6_dst_idev(&rt->dst),
IPSTATS_MIB_FRAGOKS);
+ rcu_read_unlock();
return 0;
}

@@ -949,6 +953,7 @@ int ip6_fragment(struct net *net, struct sock *sk, struct sk_buff *skb,

IP6_INC_STATS(net, ip6_dst_idev(&rt->dst),
IPSTATS_MIB_FRAGFAILS);
+ rcu_read_unlock();
return err;

slow_path_clean:
--
2.35.1