Subject: KASAN: use-after-free Read in rxrpc_send_data_packet

From: syzbot <[email-masked]>
Date: Mon, 01 Feb 2021 00:03:19 -0800

Hello,

syzbot found the following issue on:

HEAD commit:    78031381 bpf: Drop disabled LSM hooks from the sleepable set
git tree:       bpf
console output: https://syzkaller.appspot.com/x/log.txt?x=11274530d00000
kernel config:  https://syzkaller.appspot.com/x/.config?x=be33d8015c9de024
dashboard link: https://syzkaller.appspot.com/bug?extid=174de899852504e4a74a
compiler:       gcc (GCC) 10.1.0-syz 20200507

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: [email-masked]

==================================================================
BUG: KASAN: use-after-free in rxrpc_send_data_packet+0x19b4/0x1e70 net/rxrpc/output.c:372
Read of size 4 at addr ffff888011606e04 by task kworker/0:0/5

CPU: 0 PID: 5 Comm: kworker/0:0 Not tainted 5.11.0-rc4-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
Workqueue: krxrpcd rxrpc_process_call
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
 rxrpc_send_data_packet+0x19b4/0x1e70 net/rxrpc/output.c:372
 rxrpc_resend net/rxrpc/call_event.c:266 [inline]
 rxrpc_process_call+0x1634/0x1f60 net/rxrpc/call_event.c:412
 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

Allocated by task 2318:
 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
 kasan_slab_alloc include/linux/kasan.h:209 [inline]
 slab_post_alloc_hook mm/slab.h:512 [inline]
 slab_alloc_node mm/slub.c:2891 [inline]
 kmem_cache_alloc_node+0x1e0/0x470 mm/slub.c:2927
 __alloc_skb+0x71/0x5a0 net/core/skbuff.c:198
 alloc_skb include/linux/skbuff.h:1099 [inline]
 alloc_skb_with_frags+0x93/0x5d0 net/core/skbuff.c:5894
 sock_alloc_send_pskb+0x793/0x920 net/core/sock.c:2348
 rxrpc_send_data+0xb51/0x2bf0 net/rxrpc/sendmsg.c:358
 rxrpc_do_sendmsg+0xc03/0x1350 net/rxrpc/sendmsg.c:744
 rxrpc_sendmsg+0x420/0x630 net/rxrpc/af_rxrpc.c:560
 sock_sendmsg_nosec net/socket.c:652 [inline]
 sock_sendmsg+0xcf/0x120 net/socket.c:672
 ____sys_sendmsg+0x6e8/0x810 net/socket.c:2345
 ___sys_sendmsg+0xf3/0x170 net/socket.c:2399
 __sys_sendmsg+0xe5/0x1b0 net/socket.c:2432
 do_syscall_64+0x2d/0x70 arch/x86/entry/common.c:46
 entry_SYSCALL_64_after_hwframe+0x44/0xa9

Freed by task 2318:
 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:3142 [inline]
 kmem_cache_free+0x82/0x350 mm/slub.c:3158
 kfree_skbmem+0xef/0x1b0 net/core/skbuff.c:636
 __kfree_skb net/core/skbuff.c:693 [inline]
 kfree_skb net/core/skbuff.c:710 [inline]
 kfree_skb+0x140/0x3f0 net/core/skbuff.c:704
 rxrpc_free_skb+0x11d/0x150 net/rxrpc/skbuff.c:78
 rxrpc_cleanup_ring net/rxrpc/call_object.c:485 [inline]
 rxrpc_release_call+0x5dd/0x860 net/rxrpc/call_object.c:552
 rxrpc_release_calls_on_socket+0x21c/0x300 net/rxrpc/call_object.c:579
 rxrpc_release_sock net/rxrpc/af_rxrpc.c:885 [inline]
 rxrpc_release+0x263/0x5a0 net/rxrpc/af_rxrpc.c:916
 __sock_release+0xcd/0x280 net/socket.c:597
 sock_close+0x18/0x20 net/socket.c:1256
 __fput+0x283/0x920 fs/file_table.c:280
 task_work_run+0xdd/0x190 kernel/task_work.c:140
 get_signal+0x1c7f/0x20f0 kernel/signal.c:2554
 arch_do_signal_or_restart+0x2a8/0x1eb0 arch/x86/kernel/signal.c:811
 handle_signal_work kernel/entry/common.c:147 [inline]
 exit_to_user_mode_loop kernel/entry/common.c:171 [inline]
 exit_to_user_mode_prepare+0x148/0x250 kernel/entry/common.c:201
 __syscall_exit_to_user_mode_work kernel/entry/common.c:291 [inline]
 syscall_exit_to_user_mode+0x19/0x50 kernel/entry/common.c:302
 entry_SYSCALL_64_after_hwframe+0x44/0xa9

The buggy address belongs to the object at ffff888011606dc0
 which belongs to the cache skbuff_head_cache of size 232
The buggy address is located 68 bytes inside of
 232-byte region [ffff888011606dc0, ffff888011606ea8)
The buggy address belongs to the page:
page:0000000003512b7c refcount:1 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x11606
flags: 0xfff00000000200(slab)
raw: 00fff00000000200 ffffea00008b6e00 0000000b0000000b ffff888010cbbc80
raw: 0000000000000000 00000000000c000c 00000001ffffffff 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
 ffff888011606d00: fb fb fb fb fb fb fb fb fb fb fb fb fb fc fc fc
 ffff888011606d80: fc fc fc fc fc fc fc fc fa fb fb fb fb fb fb fb
>ffff888011606e00: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
                   ^
 ffff888011606e80: fb fb fb fb fb fc fc fc fc fc fc fc fc fc fc fc
 ffff888011606f00: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
==================================================================

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