KASAN: use-after-free Read in route4_get

[syzbot]

Hello,

syzbot found the following crash on:

HEAD commit: e6e6ec48 Merge tag 'fscrypt-for-linus' of git://git.kernel..
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=14982f53e00000
kernel config: https://syzkaller.appspot.com/x/.config?x=a5295e161cd85b82
dashboard link: https://syzkaller.appspot.com/bug?extid=1cba26af4a37d30e8040
compiler: clang version 10.0.0 (https://github.com/llvm/llvm-project/ c2443155a0fb245c8f17f2c1c72b6ea391e86e81)

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

IMPORTANT: if you fix the bug, please add the following tag to the commit:
Reported-by: syzbot+1cba26...@syzkaller.appspotmail.com

==================================================================
BUG: KASAN: use-after-free in route4_get+0x351/0x380 net/sched/cls_route.c:235
Read of size 4 at addr ffff8880a0d70040 by task syz-executor.0/9234

CPU: 0 PID: 9234 Comm: syz-executor.0 Not tainted 5.6.0-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+0x1e9/0x30e lib/dump_stack.c:118
print_address_description+0x74/0x5c0 mm/kasan/report.c:374
__kasan_report+0x14b/0x1c0 mm/kasan/report.c:506
kasan_report+0x25/0x50 mm/kasan/common.c:641
route4_get+0x351/0x380 net/sched/cls_route.c:235
tc_new_tfilter+0x111c/0x2f50 net/sched/cls_api.c:2082
rtnetlink_rcv_msg+0x8fb/0xd40 net/core/rtnetlink.c:5427
netlink_rcv_skb+0x190/0x3a0 net/netlink/af_netlink.c:2478
netlink_unicast_kernel net/netlink/af_netlink.c:1303 [inline]
netlink_unicast+0x786/0x940 net/netlink/af_netlink.c:1329
netlink_sendmsg+0xa57/0xd70 net/netlink/af_netlink.c:1918
sock_sendmsg_nosec net/socket.c:652 [inline]
sock_sendmsg net/socket.c:672 [inline]
____sys_sendmsg+0x4f9/0x7c0 net/socket.c:2343
___sys_sendmsg net/socket.c:2397 [inline]
__sys_sendmsg+0x1ed/0x290 net/socket.c:2430
do_syscall_64+0xf3/0x1b0 arch/x86/entry/common.c:294
entry_SYSCALL_64_after_hwframe+0x49/0xbe
RIP: 0033:0x45c679
Code: ad b6 fb ff c3 66 2e 0f 1f 84 00 00 00 00 00 66 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 0f 83 7b b6 fb ff c3 66 2e 0f 1f 84 00 00 00 00
RSP: 002b:00007f7755ac4c78 EFLAGS: 00000246 ORIG_RAX: 000000000000002e
RAX: ffffffffffffffda RBX: 00007f7755ac56d4 RCX: 000000000045c679
RDX: 0000000000000000 RSI: 0000000020000280 RDI: 0000000000000007
RBP: 000000000076bfa0 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 00000000ffffffff
R13: 00000000000009fa R14: 00000000004cc948 R15: 000000000076bfac

Allocated by task 9226:
save_stack mm/kasan/common.c:72 [inline]
set_track mm/kasan/common.c:80 [inline]
__kasan_kmalloc+0x118/0x1c0 mm/kasan/common.c:515
kmem_cache_alloc_trace+0x234/0x300 mm/slab.c:3551
kmalloc include/linux/slab.h:555 [inline]
kzalloc include/linux/slab.h:669 [inline]
route4_change+0x224/0x1d90 net/sched/cls_route.c:493
tc_new_tfilter+0x1490/0x2f50 net/sched/cls_api.c:2103
rtnetlink_rcv_msg+0x8fb/0xd40 net/core/rtnetlink.c:5427
netlink_rcv_skb+0x190/0x3a0 net/netlink/af_netlink.c:2478
netlink_unicast_kernel net/netlink/af_netlink.c:1303 [inline]
netlink_unicast+0x786/0x940 net/netlink/af_netlink.c:1329
netlink_sendmsg+0xa57/0xd70 net/netlink/af_netlink.c:1918
sock_sendmsg_nosec net/socket.c:652 [inline]
sock_sendmsg net/socket.c:672 [inline]
____sys_sendmsg+0x4f9/0x7c0 net/socket.c:2343
___sys_sendmsg net/socket.c:2397 [inline]
__sys_sendmsg+0x1ed/0x290 net/socket.c:2430
do_syscall_64+0xf3/0x1b0 arch/x86/entry/common.c:294
entry_SYSCALL_64_after_hwframe+0x49/0xbe

Freed by task 144:
save_stack mm/kasan/common.c:72 [inline]
set_track mm/kasan/common.c:80 [inline]
kasan_set_free_info mm/kasan/common.c:337 [inline]
__kasan_slab_free+0x12e/0x1e0 mm/kasan/common.c:476
__cache_free mm/slab.c:3426 [inline]
kfree+0x10a/0x220 mm/slab.c:3757
__route4_delete_filter net/sched/cls_route.c:257 [inline]
route4_delete_filter_work+0xb1/0xe0 net/sched/cls_route.c:266
process_one_work+0x76e/0xfd0 kernel/workqueue.c:2266
worker_thread+0xa7f/0x1450 kernel/workqueue.c:2412
kthread+0x317/0x340 kernel/kthread.c:255
ret_from_fork+0x24/0x30 arch/x86/entry/entry_64.S:352

The buggy address belongs to the object at ffff8880a0d70000
which belongs to the cache kmalloc-192 of size 192
The buggy address is located 64 bytes inside of
192-byte region [ffff8880a0d70000, ffff8880a0d700c0)
The buggy address belongs to the page:
page:ffffea0002835c00 refcount:1 mapcount:0 mapping:ffff8880aa400000 index:0x0
flags: 0xfffe0000000200(slab)
raw: 00fffe0000000200 ffffea0002830e08 ffffea000263c548 ffff8880aa400000
raw: 0000000000000000 ffff8880a0d70000 0000000100000010 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
ffff8880a0d6ff00: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
ffff8880a0d6ff80: fb fb fb fb fb fb fb fc fc fc fc fc fc fc fc fc
>ffff8880a0d70000: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
^
ffff8880a0d70080: fb fb fb fb fb fb fb fb fc fc fc fc fc fc fc fc
ffff8880a0d70100: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
==================================================================


---
This bug is generated by a bot. It may contain errors.
See https://goo.gl/tpsmEJ for more information about syzbot.
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[Hillf Danton]

On Fri, 13 Mar 2020 00:24:09 -0700

Add rcu_read_lock() in an attempt to work out why rtnl_dereference()
failed to provide protection for readers.

--- a/net/sched/cls_route.c
+++ b/net/sched/cls_route.c
@@ -227,14 +227,18 @@ static void *route4_get(struct tcf_proto
if (h2 > 32)
return NULL;

+ rcu_read_lock();
b = rtnl_dereference(head->table[h1]);
if (b) {
for (f = rtnl_dereference(b->ht[h2]);
f;
f = rtnl_dereference(f->next))
- if (f->handle == handle)
+ if (f->handle == handle) {
+ rcu_read_unlock();
return f;
+ }
}
+ rcu_read_unlock();
return NULL;
}

[Cong Wang]

#syz fix: net_sched: cls_route: remove the right filter from hashtable

[syzbot]

syzbot has found a reproducer for the following crash on:

HEAD commit: 5076190d mm: slub: be more careful about the double cmpxch..
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=1645af81e00000
kernel config: https://syzkaller.appspot.com/x/.config?x=9f894bd92023de02
dashboard link: https://syzkaller.appspot.com/bug?extid=1cba26af4a37d30e8040
compiler: gcc (GCC) 9.0.0 20181231 (experimental)
syz repro: https://syzkaller.appspot.com/x/repro.syz?x=14a2c5f9e00000
C reproducer: https://syzkaller.appspot.com/x/repro.c?x=145da7c3e00000

IMPORTANT: if you fix the bug, please add the following tag to the commit:
Reported-by: syzbot+1cba26...@syzkaller.appspotmail.com

==================================================================

BUG: KASAN: use-after-free in route4_get+0x3e1/0x420 net/sched/cls_route.c:235
Read of size 4 at addr ffff8880a6ad6340 by task syz-executor193/9646

CPU: 1 PID: 9646 Comm: syz-executor193 Not tainted 5.6.0-rc6-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+0x188/0x20d lib/dump_stack.c:118
print_address_description.constprop.0.cold+0xd3/0x315 mm/kasan/report.c:374
__kasan_report.cold+0x1a/0x32 mm/kasan/report.c:506
kasan_report+0xe/0x20 mm/kasan/common.c:641
route4_get+0x3e1/0x420 net/sched/cls_route.c:235
tc_new_tfilter+0x7a9/0x20b0 net/sched/cls_api.c:2082
rtnetlink_rcv_msg+0x810/0xad0 net/core/rtnetlink.c:5427
netlink_rcv_skb+0x15a/0x410 net/netlink/af_netlink.c:2478
netlink_unicast_kernel net/netlink/af_netlink.c:1303 [inline]
netlink_unicast+0x537/0x740 net/netlink/af_netlink.c:1329
netlink_sendmsg+0x882/0xe10 net/netlink/af_netlink.c:1918
sock_sendmsg_nosec net/socket.c:652 [inline]
sock_sendmsg+0xcf/0x120 net/socket.c:672
____sys_sendmsg+0x6b9/0x7d0 net/socket.c:2343
___sys_sendmsg+0x100/0x170 net/socket.c:2397
__sys_sendmsg+0xec/0x1b0 net/socket.c:2430
do_syscall_64+0xf6/0x7d0 arch/x86/entry/common.c:294
entry_SYSCALL_64_after_hwframe+0x49/0xbe
RIP: 0033:0x44c3d9
Code: e8 7c e6 ff ff 48 83 c4 18 c3 0f 1f 80 00 00 00 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 0f 83 1b 05 fc ff c3 66 2e 0f 1f 84 00 00 00 00
RSP: 002b:00007f51dd98ace8 EFLAGS: 00000246 ORIG_RAX: 000000000000002e
RAX: ffffffffffffffda RBX: 00000000006e8a28 RCX: 000000000044c3d9

RDX: 0000000000000000 RSI: 0000000020000280 RDI: 0000000000000007

RBP: 00000000006e8a20 R08: 0000000000000065 R09: 0000000000000000
R10: 0000000000000014 R11: 0000000000000246 R12: 00000000006e8a2c
R13: 00007fff6ce670bf R14: 00007f51dd98b9c0 R15: 20c49ba5e353f7cf

Allocated by task 9646:
save_stack+0x1b/0x80 mm/kasan/common.c:72
set_track mm/kasan/common.c:80 [inline]
__kasan_kmalloc mm/kasan/common.c:515 [inline]
__kasan_kmalloc.constprop.0+0xbf/0xd0 mm/kasan/common.c:488
kmem_cache_alloc_trace+0x153/0x7d0 mm/slab.c:3551

kmalloc include/linux/slab.h:555 [inline]
kzalloc include/linux/slab.h:669 [inline]

route4_change+0x2a9/0x2250 net/sched/cls_route.c:493
tc_new_tfilter+0xa59/0x20b0 net/sched/cls_api.c:2103
rtnetlink_rcv_msg+0x810/0xad0 net/core/rtnetlink.c:5427
netlink_rcv_skb+0x15a/0x410 net/netlink/af_netlink.c:2478
netlink_unicast_kernel net/netlink/af_netlink.c:1303 [inline]
netlink_unicast+0x537/0x740 net/netlink/af_netlink.c:1329
netlink_sendmsg+0x882/0xe10 net/netlink/af_netlink.c:1918
sock_sendmsg_nosec net/socket.c:652 [inline]
sock_sendmsg+0xcf/0x120 net/socket.c:672
____sys_sendmsg+0x6b9/0x7d0 net/socket.c:2343
___sys_sendmsg+0x100/0x170 net/socket.c:2397
__sys_sendmsg+0xec/0x1b0 net/socket.c:2430
do_syscall_64+0xf6/0x7d0 arch/x86/entry/common.c:294
entry_SYSCALL_64_after_hwframe+0x49/0xbe

Freed by task 7:
save_stack+0x1b/0x80 mm/kasan/common.c:72

set_track mm/kasan/common.c:80 [inline]
kasan_set_free_info mm/kasan/common.c:337 [inline]

__kasan_slab_free+0xf7/0x140 mm/kasan/common.c:476
__cache_free mm/slab.c:3426 [inline]
kfree+0x109/0x2b0 mm/slab.c:3757
route4_delete_filter_work+0x17/0x20 net/sched/cls_route.c:266
process_one_work+0x94b/0x1690 kernel/workqueue.c:2266
worker_thread+0x96/0xe20 kernel/workqueue.c:2412
kthread+0x357/0x430 kernel/kthread.c:255
ret_from_fork+0x24/0x30 arch/x86/entry/entry_64.S:352

The buggy address belongs to the object at ffff8880a6ad6300

which belongs to the cache kmalloc-192 of size 192
The buggy address is located 64 bytes inside of

192-byte region [ffff8880a6ad6300, ffff8880a6ad63c0)

The buggy address belongs to the page:

page:ffffea00029ab580 refcount:1 mapcount:0 mapping:ffff8880aa000000 index:0x0
flags: 0xfffe0000000200(slab)
raw: 00fffe0000000200 ffffea00023ceec8 ffffea00024bc688 ffff8880aa000000
raw: 0000000000000000 ffff8880a6ad6000 0000000100000010 0000000000000000

page dumped because: kasan: bad access detected

Memory state around the buggy address:

ffff8880a6ad6200: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
ffff8880a6ad6280: 00 00 00 00 00 00 fc fc fc fc fc fc fc fc fc fc
>ffff8880a6ad6300: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
^
ffff8880a6ad6380: fb fb fb fb fb fb fb fb fc fc fc fc fc fc fc fc
ffff8880a6ad6400: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
==================================================================