net: use-after-free in worker_thread

[Andrey Konovalov]

Hi!

I'm seeing lots of the following error reports while running the
syzkaller fuzzer.

Reports appeared when I updated to 3c49de52 (Dec 2) from 2caceb32 (Dec 1).

==================================================================
BUG: KASAN: use-after-free in worker_thread+0x17d8/0x18a0
Read of size 8 at addr ffff880067f3ecd8 by task kworker/3:1/774

page:ffffea00019fce00 count:1 mapcount:0 mapping:          (null)
index:0xffff880067f39c10 compound_mapcount: 0
flags: 0x500000000004080(slab|head)
page dumped because: kasan: bad access detected

CPU: 3 PID: 774 Comm: kworker/3:1 Not tainted 4.9.0-rc7+ #66
Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS Bochs 01/01/2011
 ffff88006c267838 ffffffff81f882da ffffffff6c25e338 1ffff1000d84ce9a
 ffffed000d84ce92 ffff88006c25e340 0000000041b58ab3 ffffffff8541e198
 ffffffff81f88048 0000000100000000 0000000041b58ab3 ffffffff853d3ee8
Call Trace:
 [<     inline     >] __dump_stack lib/dump_stack.c:15
 [<ffffffff81f882da>] dump_stack+0x292/0x398 lib/dump_stack.c:51
 [<     inline     >] describe_address mm/kasan/report.c:262
 [<ffffffff817e50d1>] kasan_report_error+0x121/0x560 mm/kasan/report.c:368
 [<     inline     >] kasan_report mm/kasan/report.c:390
 [<ffffffff817e560e>] __asan_report_load8_noabort+0x3e/0x40
mm/kasan/report.c:411
 [<ffffffff81329b88>] worker_thread+0x17d8/0x18a0 kernel/workqueue.c:2228
 [<ffffffff8133ebf3>] kthread+0x323/0x3e0 kernel/kthread.c:209
 [<ffffffff84a2a22a>] ret_from_fork+0x2a/0x40 arch/x86/entry/entry_64.S:433

The buggy address belongs to the object at ffff880067f3e6d0
 which belongs to the cache kmalloc-2048 of size 2048
The buggy address ffff880067f3ecd8 is located 1544 bytes inside
 of 2048-byte region [ffff880067f3e6d0, ffff880067f3eed0)

Freed by task 0:
 [<ffffffff81203526>] save_stack_trace+0x16/0x20 arch/x86/kernel/stacktrace.c:57
 [<ffffffff817e4173>] save_stack+0x43/0xd0 mm/kasan/kasan.c:495
 [<     inline     >] set_track mm/kasan/kasan.c:507
 [<ffffffff817e4a53>] kasan_slab_free+0x73/0xc0 mm/kasan/kasan.c:571
 [<     inline     >] slab_free_hook mm/slub.c:1352
 [<     inline     >] slab_free_freelist_hook mm/slub.c:1374
 [<     inline     >] slab_free mm/slub.c:2951
 [<ffffffff817e0eb7>] kfree+0xe7/0x2b0 mm/slub.c:3871
 [<     inline     >] sk_prot_free net/core/sock.c:1372
 [<ffffffff831ea1c7>] __sk_destruct+0x5c7/0x6e0 net/core/sock.c:1445
 [<ffffffff831f3517>] sk_destruct+0x47/0x80 net/core/sock.c:1453
 [<ffffffff831f35a7>] __sk_free+0x57/0x230 net/core/sock.c:1461
 [<ffffffff831f37a3>] sk_free+0x23/0x30 net/core/sock.c:1472
 [<     inline     >] sock_put include/net/sock.h:1591
 [<ffffffff8348ca9c>] deferred_put_nlk_sk+0x2c/0x40 net/netlink/af_netlink.c:671
 [<     inline     >] __rcu_reclaim kernel/rcu/rcu.h:118
 [<ffffffff8146d42f>] rcu_do_batch.isra.67+0x8ff/0xc50 kernel/rcu/tree.c:2776
 [<     inline     >] invoke_rcu_callbacks kernel/rcu/tree.c:3040
 [<     inline     >] __rcu_process_callbacks kernel/rcu/tree.c:3007
 [<ffffffff8146e097>] rcu_process_callbacks+0x2b7/0xba0 kernel/rcu/tree.c:3024
 [<ffffffff84a2d08b>] __do_softirq+0x2fb/0xb63 kernel/softirq.c:284

Allocated by task 10748:
 [<ffffffff81203526>] save_stack_trace+0x16/0x20 arch/x86/kernel/stacktrace.c:57
 [<ffffffff817e4173>] save_stack+0x43/0xd0 mm/kasan/kasan.c:495
 [<     inline     >] set_track mm/kasan/kasan.c:507
 [<ffffffff817e43fd>] kasan_kmalloc+0xad/0xe0 mm/kasan/kasan.c:598
 [<ffffffff817e0050>] __kmalloc+0xa0/0x2d0 mm/slub.c:3734
 [<     inline     >] kmalloc include/linux/slab.h:495
 [<ffffffff831e4c01>] sk_prot_alloc+0x101/0x2a0 net/core/sock.c:1333
 [<ffffffff831efd15>] sk_alloc+0x105/0x1000 net/core/sock.c:1389
 [<ffffffff8348ad46>] __netlink_create+0x66/0x1d0 net/netlink/af_netlink.c:588
 [<ffffffff8348cdab>] netlink_create+0x2fb/0x500 net/netlink/af_netlink.c:647
 [<ffffffff831dd1d6>] __sock_create+0x4f6/0x880 net/socket.c:1168
 [<     inline     >] sock_create net/socket.c:1208
 [<     inline     >] SYSC_socket net/socket.c:1238
 [<ffffffff831dd799>] SyS_socket+0xf9/0x230 net/socket.c:1218
 [<ffffffff84a29fc1>] entry_SYSCALL_64_fastpath+0x1f/0xc2

Memory state around the buggy address:
 ffff880067f3eb80: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff880067f3ec00: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>ffff880067f3ec80: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
                                                    ^
 ffff880067f3ed00: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff880067f3ed80: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
==================================================================