Latest commit 853697504d ("tcp: Fix highest_sack and highest_sack_seq")
apparently allowed syzbot to trigger various crashes in TCP stack [1]
I believe this commit only made things easier for syzbot to find
its way into triggering use-after-frees. But really the bugs
could lead to bad TCP behavior or even plain crashes even for
non malicious peers.
I have audited all calls to tcp_rtx_queue_unlink() and
tcp_rtx_queue_unlink_and_free() and made sure tp->highest_sack would be updated
if we are removing from rtx queue the skb that tp->highest_sack points to.
These updates were missing in three locations :
1) tcp_clean_rtx_queue() [This one seems quite serious,
I have no idea why this was not caught earlier]
2) tcp_rtx_queue_purge() [Probably not a big deal for normal operations]
3) tcp_send_synack() [Probably not a big deal for normal operations]
[1]
BUG: KASAN: use-after-free in tcp_highest_sack_seq include/net/tcp.h:1864 [inline]
BUG: KASAN: use-after-free in tcp_highest_sack_seq include/net/tcp.h:1856 [inline]
BUG: KASAN: use-after-free in tcp_check_sack_reordering+0x33c/0x3a0 net/ipv4/tcp_input.c:891
Read of size 4 at addr ffff8880a488d068 by task ksoftirqd/1/16
CPU: 1 PID: 16 Comm: ksoftirqd/1 Not tainted 5.5.0-rc5-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
Call Trace:
__dump_stack lib/dump_stack.c:77 [inline]
dump_stack+0x197/0x210 lib/dump_stack.c:118
print_address_description.constprop.0.cold+0xd4/0x30b mm/kasan/report.c:374
__kasan_report.cold+0x1b/0x41 mm/kasan/report.c:506
kasan_report+0x12/0x20 mm/kasan/common.c:639
__asan_report_load4_noabort+0x14/0x20 mm/kasan/generic_report.c:134
tcp_highest_sack_seq include/net/tcp.h:1864 [inline]
tcp_highest_sack_seq include/net/tcp.h:1856 [inline]
tcp_check_sack_reordering+0x33c/0x3a0 net/ipv4/tcp_input.c:891
tcp_try_undo_partial net/ipv4/tcp_input.c:2730 [inline]
tcp_fastretrans_alert+0xf74/0x23f0 net/ipv4/tcp_input.c:2847
tcp_ack+0x2577/0x5bf0 net/ipv4/tcp_input.c:3710
tcp_rcv_established+0x6dd/0x1e90 net/ipv4/tcp_input.c:5706
tcp_v4_do_rcv+0x619/0x8d0 net/ipv4/tcp_ipv4.c:1619
tcp_v4_rcv+0x307f/0x3b40 net/ipv4/tcp_ipv4.c:2001
ip_protocol_deliver_rcu+0x5a/0x880 net/ipv4/ip_input.c:204
ip_local_deliver_finish+0x23b/0x380 net/ipv4/ip_input.c:231
NF_HOOK include/linux/netfilter.h:307 [inline]
NF_HOOK include/linux/netfilter.h:301 [inline]
ip_local_deliver+0x1e9/0x520 net/ipv4/ip_input.c:252
dst_input include/net/dst.h:442 [inline]
ip_rcv_finish+0x1db/0x2f0 net/ipv4/ip_input.c:428
NF_HOOK include/linux/netfilter.h:307 [inline]
NF_HOOK include/linux/netfilter.h:301 [inline]
ip_rcv+0xe8/0x3f0 net/ipv4/ip_input.c:538
__netif_receive_skb_one_core+0x113/0x1a0 net/core/dev.c:5148
__netif_receive_skb+0x2c/0x1d0 net/core/dev.c:5262
process_backlog+0x206/0x750 net/core/dev.c:6093
napi_poll net/core/dev.c:6530 [inline]
net_rx_action+0x508/0x1120 net/core/dev.c:6598
__do_softirq+0x262/0x98c kernel/softirq.c:292
run_ksoftirqd kernel/softirq.c:603 [inline]
run_ksoftirqd+0x8e/0x110 kernel/softirq.c:595
smpboot_thread_fn+0x6a3/0xa40 kernel/smpboot.c:165
kthread+0x361/0x430 kernel/kthread.c:255
ret_from_fork+0x24/0x30 arch/x86/entry/entry_64.S:352
Allocated by task 10091:
save_stack+0x23/0x90 mm/kasan/common.c:72
set_track mm/kasan/common.c:80 [inline]
__kasan_kmalloc mm/kasan/common.c:513 [inline]
__kasan_kmalloc.constprop.0+0xcf/0xe0 mm/kasan/common.c:486
kasan_slab_alloc+0xf/0x20 mm/kasan/common.c:521
slab_post_alloc_hook mm/slab.h:584 [inline]
slab_alloc_node mm/slab.c:3263 [inline]
kmem_cache_alloc_node+0x138/0x740 mm/slab.c:3575
__alloc_skb+0xd5/0x5e0 net/core/skbuff.c:198
alloc_skb_fclone include/linux/skbuff.h:1099 [inline]
sk_stream_alloc_skb net/ipv4/tcp.c:875 [inline]
sk_stream_alloc_skb+0x113/0xc90 net/ipv4/tcp.c:852
tcp_sendmsg_locked+0xcf9/0x3470 net/ipv4/tcp.c:1282
tcp_sendmsg+0x30/0x50 net/ipv4/tcp.c:1432
inet_sendmsg+0x9e/0xe0 net/ipv4/af_inet.c:807
sock_sendmsg_nosec net/socket.c:652 [inline]
sock_sendmsg+0xd7/0x130 net/socket.c:672
__sys_sendto+0x262/0x380 net/socket.c:1998
__do_sys_sendto net/socket.c:2010 [inline]
__se_sys_sendto net/socket.c:2006 [inline]
__x64_sys_sendto+0xe1/0x1a0 net/socket.c:2006
do_syscall_64+0xfa/0x790 arch/x86/entry/common.c:294
entry_SYSCALL_64_after_hwframe+0x49/0xbe
Freed by task 10095:
save_stack+0x23/0x90 mm/kasan/common.c:72
set_track mm/kasan/common.c:80 [inline]
kasan_set_free_info mm/kasan/common.c:335 [inline]
__kasan_slab_free+0x102/0x150 mm/kasan/common.c:474
kasan_slab_free+0xe/0x10 mm/kasan/common.c:483
__cache_free mm/slab.c:3426 [inline]
kmem_cache_free+0x86/0x320 mm/slab.c:3694
kfree_skbmem+0x178/0x1c0 net/core/skbuff.c:645
__kfree_skb+0x1e/0x30 net/core/skbuff.c:681
sk_eat_skb include/net/sock.h:2453 [inline]
tcp_recvmsg+0x1252/0x2930 net/ipv4/tcp.c:2166
inet_recvmsg+0x136/0x610 net/ipv4/af_inet.c:838
sock_recvmsg_nosec net/socket.c:886 [inline]
sock_recvmsg net/socket.c:904 [inline]
sock_recvmsg+0xce/0x110 net/socket.c:900
__sys_recvfrom+0x1ff/0x350 net/socket.c:2055
__do_sys_recvfrom net/socket.c:2073 [inline]
__se_sys_recvfrom net/socket.c:2069 [inline]
__x64_sys_recvfrom+0xe1/0x1a0 net/socket.c:2069
do_syscall_64+0xfa/0x790 arch/x86/entry/common.c:294
entry_SYSCALL_64_after_hwframe+0x49/0xbe
The buggy address belongs to the object at ffff8880a488d040
which belongs to the cache skbuff_fclone_cache of size 456
The buggy address is located 40 bytes inside of
456-byte region [ffff8880a488d040, ffff8880a488d208)
The buggy address belongs to the page:
page:ffffea0002922340 refcount:1 mapcount:0 mapping:ffff88821b057000 index:0x0
raw: 00fffe0000000200 ffffea00022a5788 ffffea0002624a48 ffff88821b057000
raw: 0000000000000000 ffff8880a488d040 0000000100000006 0000000000000000
page dumped because: kasan: bad access detected
Memory state around the buggy address:
ffff8880a488cf00: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
ffff8880a488cf80: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
>ffff8880a488d000: fc fc fc fc fc fc fc fc fb fb fb fb fb fb fb fb
^
ffff8880a488d080: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
ffff8880a488d100: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
Fixes: 853697504d ("tcp: Fix highest_sack and highest_sack_seq")
Fixes: 50895b9de1 ("tcp: highest_sack fix")
Fixes: 737ff31456 ("tcp: use sequence distance to detect reordering")
Signed-off-by: Eric Dumazet <edumazet@google.com>
Cc: Cambda Zhu <cambda@linux.alibaba.com>
Cc: Yuchung Cheng <ycheng@google.com>
Cc: Neal Cardwell <ncardwell@google.com>
Acked-by: Neal Cardwell <ncardwell@google.com>
Acked-by: Yuchung Cheng <ycheng@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
2bec445f9b