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Date:   Mon, 20 Jul 2020 21:41:20 -0700
From:   syzbot <>
Subject: KASAN: use-after-free Read in sock_def_write_space (2)


syzbot found the following issue on:

HEAD commit:    5714ee50 copy_xstate_to_kernel: Fix typo which caused GDB ..
git tree:       upstream
console output:
kernel config:
dashboard link:
compiler:       gcc (GCC) 10.1.0-syz 20200507
userspace arch: i386
syz repro:
C reproducer:

IMPORTANT: if you fix the issue, please add the following tag to the commit:

IPVS: ftp: loaded support on port[0] = 21
BUG: KASAN: use-after-free in list_empty include/linux/list.h:282 [inline]
BUG: KASAN: use-after-free in waitqueue_active include/linux/wait.h:127 [inline]
BUG: KASAN: use-after-free in wq_has_sleeper include/linux/wait.h:161 [inline]
BUG: KASAN: use-after-free in skwq_has_sleeper include/net/sock.h:2143 [inline]
BUG: KASAN: use-after-free in sock_def_write_space+0x609/0x630 net/core/sock.c:2926
Read of size 8 at addr ffff88808a6d25c0 by task syz-executor863/6817

CPU: 0 PID: 6817 Comm: syz-executor863 Not tainted 5.8.0-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+0x18f/0x20d lib/dump_stack.c:118
 print_address_description.constprop.0.cold+0xae/0x436 mm/kasan/report.c:383
 __kasan_report mm/kasan/report.c:513 [inline]
 kasan_report.cold+0x1f/0x37 mm/kasan/report.c:530
 list_empty include/linux/list.h:282 [inline]
 waitqueue_active include/linux/wait.h:127 [inline]
 wq_has_sleeper include/linux/wait.h:161 [inline]
 skwq_has_sleeper include/net/sock.h:2143 [inline]
 sock_def_write_space+0x609/0x630 net/core/sock.c:2926
 sock_wfree+0x1cc/0x240 net/core/sock.c:2060
 skb_release_head_state+0x9f/0x250 net/core/skbuff.c:651
 skb_release_all net/core/skbuff.c:662 [inline]
 __kfree_skb net/core/skbuff.c:678 [inline]
 kfree_skb.part.0+0x89/0x350 net/core/skbuff.c:696
 kfree_skb+0x7d/0x100 include/linux/refcount.h:270
 skb_queue_purge+0x14/0x30 net/core/skbuff.c:3077
 qrtr_tun_release+0x40/0x60 net/qrtr/tun.c:118
 __fput+0x33c/0x880 fs/file_table.c:281
 task_work_run+0xdd/0x190 kernel/task_work.c:135
 tracehook_notify_resume include/linux/tracehook.h:188 [inline]
 exit_to_usermode_loop arch/x86/entry/common.c:239 [inline]
 __prepare_exit_to_usermode+0x1e9/0x1f0 arch/x86/entry/common.c:269
 __do_fast_syscall_32 arch/x86/entry/common.c:475 [inline]
 do_fast_syscall_32+0x7f/0x120 arch/x86/entry/common.c:503
RIP: 0023:0xf7fc2569
Code: Bad RIP value.
RSP: 002b:00000000ffd1de7c EFLAGS: 00000246 ORIG_RAX: 0000000000000006
RAX: 0000000000000000 RBX: 0000000000000006 RCX: 0000000020000180
RDX: 0000000000000007 RSI: 00000000080bffdb RDI: 000000002000018e
RBP: 00000000ffd1dee8 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000000 R12: 0000000000000000
R13: 0000000000000000 R14: 0000000000000000 R15: 0000000000000000

Allocated by task 6817:
 save_stack+0x1b/0x40 mm/kasan/common.c:48
 set_track mm/kasan/common.c:56 [inline]
 __kasan_kmalloc.constprop.0+0xc2/0xd0 mm/kasan/common.c:494
 slab_post_alloc_hook mm/slab.h:586 [inline]
 slab_alloc mm/slab.c:3320 [inline]
 kmem_cache_alloc+0x12c/0x3b0 mm/slab.c:3484
 sock_alloc_inode+0x18/0x1c0 net/socket.c:253
 alloc_inode+0x61/0x230 fs/inode.c:232
 new_inode_pseudo+0x14/0xe0 fs/inode.c:928
 sock_alloc+0x3c/0x260 net/socket.c:573
 __sock_create+0xb9/0x740 net/socket.c:1392
 sock_create net/socket.c:1479 [inline]
 __sys_socket+0xef/0x200 net/socket.c:1521
 __do_sys_socket net/socket.c:1530 [inline]
 __se_sys_socket net/socket.c:1528 [inline]
 __ia32_sys_socket+0x6f/0xb0 net/socket.c:1528
 do_syscall_32_irqs_on+0x3f/0x60 arch/x86/entry/common.c:428
 __do_fast_syscall_32 arch/x86/entry/common.c:475 [inline]
 do_fast_syscall_32+0x7f/0x120 arch/x86/entry/common.c:503

Freed by task 16:
 save_stack+0x1b/0x40 mm/kasan/common.c:48
 set_track mm/kasan/common.c:56 [inline]
 kasan_set_free_info mm/kasan/common.c:316 [inline]
 __kasan_slab_free+0xf5/0x140 mm/kasan/common.c:455
 __cache_free mm/slab.c:3426 [inline]
 kmem_cache_free+0x7f/0x310 mm/slab.c:3694
 i_callback+0x3f/0x70 fs/inode.c:221
 rcu_do_batch kernel/rcu/tree.c:2414 [inline]
 rcu_core+0x5c7/0x1160 kernel/rcu/tree.c:2641
 __do_softirq+0x34c/0xa60 kernel/softirq.c:292

The buggy address belongs to the object at ffff88808a6d2540
 which belongs to the cache sock_inode_cache of size 1216
The buggy address is located 128 bytes inside of
 1216-byte region [ffff88808a6d2540, ffff88808a6d2a00)
The buggy address belongs to the page:
page:ffffea000229b480 refcount:1 mapcount:0 mapping:0000000000000000 index:0xffff88808a6d2ffd
flags: 0xfffe0000000200(slab)
raw: 00fffe0000000200 ffffea0002250f88 ffffea000229a608 ffff88821b77f700
raw: ffff88808a6d2ffd ffff88808a6d2000 0000000100000003 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
 ffff88808a6d2480: fb fb fb fb fb fb fb fb fc fc fc fc fc fc fc fc
 ffff88808a6d2500: fc fc fc fc fc fc fc fc fb fb fb fb fb fb fb fb
>ffff88808a6d2580: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff88808a6d2600: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff88808a6d2680: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb

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