KASAN: use-after-free Read in mptcp_established_options

From: syzbot
Date: Wed Feb 17 2021 - 12:32:13 EST

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Hello,

syzbot found the following issue on:

HEAD commit: 966df6de lan743x: sync only the received area of an rx rin..
git tree: net-next
console output: https://syzkaller.appspot.com/x/log.txt?x=11afe082d00000
kernel config: https://syzkaller.appspot.com/x/.config?x=dbc1ca9e55dc1f9f
dashboard link: https://syzkaller.appspot.com/bug?extid=3c1e5ab4997849b69807

Unfortunately, I don't have any reproducer for this issue yet.

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+3c1e5ab4997849b69807@xxxxxxxxxxxxxxxxxxxxxxxxx

==================================================================
BUG: KASAN: use-after-free in mptcp_check_fallback net/mptcp/protocol.h:745 [inline]
BUG: KASAN: use-after-free in mptcp_established_options+0x22cf/0x2780 net/mptcp/options.c:724
Read of size 8 at addr ffff88802bea10a0 by task syz-executor.1/11042

CPU: 1 PID: 11042 Comm: syz-executor.1 Not tainted 5.11.0-rc7-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
Call Trace:
__dump_stack lib/dump_stack.c:79 [inline]
dump_stack+0x107/0x163 lib/dump_stack.c:120
print_address_description.constprop.0.cold+0x5b/0x2f8 mm/kasan/report.c:230
__kasan_report mm/kasan/report.c:396 [inline]
kasan_report.cold+0x79/0xd5 mm/kasan/report.c:413
mptcp_check_fallback net/mptcp/protocol.h:745 [inline]
mptcp_established_options+0x22cf/0x2780 net/mptcp/options.c:724
tcp_established_options+0x4ed/0x700 net/ipv4/tcp_output.c:953
tcp_current_mss+0x1d2/0x360 net/ipv4/tcp_output.c:1840
tcp_send_mss+0x28/0x2b0 net/ipv4/tcp.c:943
mptcp_sendmsg_frag+0x13b/0x1220 net/mptcp/protocol.c:1266
mptcp_push_pending+0x2cc/0x650 net/mptcp/protocol.c:1477
mptcp_sendmsg+0xde4/0x2830 net/mptcp/protocol.c:1685
inet6_sendmsg+0x99/0xe0 net/ipv6/af_inet6.c:642
sock_sendmsg_nosec net/socket.c:652 [inline]
sock_sendmsg+0xcf/0x120 net/socket.c:672
sock_write_iter+0x289/0x3c0 net/socket.c:999
call_write_iter include/linux/fs.h:1901 [inline]
new_sync_write+0x426/0x650 fs/read_write.c:518
vfs_write+0x791/0xa30 fs/read_write.c:605
ksys_write+0x1ee/0x250 fs/read_write.c:658
do_syscall_64+0x2d/0x70 arch/x86/entry/common.c:46
entry_SYSCALL_64_after_hwframe+0x44/0xa9
RIP: 0033:0x465d99
Code: ff ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 40 00 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 bc ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007ff231ccc188 EFLAGS: 00000246 ORIG_RAX: 0000000000000001
RAX: ffffffffffffffda RBX: 000000000056c008 RCX: 0000000000465d99
RDX: 000000000003f9b4 RSI: 0000000020000000 RDI: 0000000000000004
RBP: 00000000004bcf27 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 000000000056c008
R13: 00007ffeaa2da27f R14: 00007ff231ccc300 R15: 0000000000022000

Allocated by task 11017:
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:401 [inline]
____kasan_kmalloc.constprop.0+0x82/0xa0 mm/kasan/common.c:429
kmalloc include/linux/slab.h:552 [inline]
kzalloc include/linux/slab.h:682 [inline]
subflow_create_ctx+0x82/0x230 net/mptcp/subflow.c:1378
subflow_ulp_init+0x62/0x370 net/mptcp/subflow.c:1459
__tcp_set_ulp net/ipv4/tcp_ulp.c:139 [inline]
tcp_set_ulp+0x27c/0x610 net/ipv4/tcp_ulp.c:160
mptcp_subflow_create_socket+0x5bf/0xe20 net/mptcp/subflow.c:1343
__mptcp_socket_create net/mptcp/protocol.c:110 [inline]
mptcp_init_sock net/mptcp/protocol.c:2365 [inline]
mptcp_init_sock+0x140/0x830 net/mptcp/protocol.c:2350
inet6_create net/ipv6/af_inet6.c:256 [inline]
inet6_create+0xa15/0x1010 net/ipv6/af_inet6.c:110
__sock_create+0x3de/0x780 net/socket.c:1406
sock_create net/socket.c:1457 [inline]
__sys_socket+0xef/0x200 net/socket.c:1499
__do_sys_socket net/socket.c:1508 [inline]
__se_sys_socket net/socket.c:1506 [inline]
__x64_sys_socket+0x6f/0xb0 net/socket.c:1506
do_syscall_64+0x2d/0x70 arch/x86/entry/common.c:46
entry_SYSCALL_64_after_hwframe+0x44/0xa9

Freed by task 10650:
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:356
____kasan_slab_free+0xe1/0x110 mm/kasan/common.c:362
kasan_slab_free include/linux/kasan.h:192 [inline]
slab_free_hook mm/slub.c:1547 [inline]
slab_free_freelist_hook+0x5d/0x150 mm/slub.c:1580
slab_free mm/slub.c:3143 [inline]
kmem_cache_free_bulk mm/slub.c:3269 [inline]
kmem_cache_free_bulk+0x253/0xc80 mm/slub.c:3256
kfree_bulk include/linux/slab.h:409 [inline]
kfree_rcu_work+0x4cd/0x860 kernel/rcu/tree.c:3226
process_one_work+0x98d/0x15f0 kernel/workqueue.c:2275
worker_thread+0x64c/0x1120 kernel/workqueue.c:2421
kthread+0x3b1/0x4a0 kernel/kthread.c:292
ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:296

The buggy address belongs to the object at ffff88802bea1000
which belongs to the cache kmalloc-256 of size 256
The buggy address is located 160 bytes inside of
256-byte region [ffff88802bea1000, ffff88802bea1100)
The buggy address belongs to the page:
page:0000000026103328 refcount:1 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x2bea0
head:0000000026103328 order:1 compound_mapcount:0
flags: 0xfff00000010200(slab|head)
raw: 00fff00000010200 dead000000000100 dead000000000122 ffff888010c413c0
raw: 0000000000000000 0000000080100010 00000001ffffffff 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
ffff88802bea0f80: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
ffff88802bea1000: fa fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>ffff88802bea1080: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
^
ffff88802bea1100: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
ffff88802bea1180: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
==================================================================

---
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