syzbot


KASAN: use-after-free Read in __sock_release
Status: fixed on 2020/10/05 13:19
Reported-by: syzbot+6e72fe680f6f0744cc9d@syzkaller.appspotmail.com
Fix commit: c5c6e00f6cc5 fix regression in "epoll: Keep a reference on files added to the check list"
First crash: 640d, last: 631d

Fix bisection: fixed by (bisect log) :
commit c5c6e00f6cc5d3ed0d6464b14e33f2f5c8505888
Author: Al Viro <viro@zeniv.linux.org.uk>
Date: Wed Sep 2 15:30:48 2020 +0000

  fix regression in "epoll: Keep a reference on files added to the check list"

similar bugs (1):
Kernel Title Repro Cause bisect Fix bisect Count Last Reported Patched Status
linux-4.19 KASAN: use-after-free Read in __sock_release 1 632d 632d 0/1 auto-closed as invalid on 2021/01/01 16:13

Sample crash report:
IPv6: ADDRCONF(NETDEV_UP): batadv_slave_1: link is not ready
batman_adv: batadv0: Interface activated: batadv_slave_1
IPv6: ADDRCONF(NETDEV_CHANGE): batadv_slave_1: link becomes ready
IPv6: ADDRCONF(NETDEV_CHANGE): veth1_to_batadv: link becomes ready
==================================================================
BUG: KASAN: use-after-free in __read_once_size include/linux/compiler.h:183 [inline]
BUG: KASAN: use-after-free in atomic64_read arch/x86/include/asm/atomic64_64.h:22 [inline]
BUG: KASAN: use-after-free in atomic_long_read include/asm-generic/atomic-long.h:45 [inline]
BUG: KASAN: use-after-free in __rwsem_down_write_failed_common kernel/locking/rwsem-xadd.c:590 [inline]
BUG: KASAN: use-after-free in rwsem_down_write_failed+0x5d7/0x6d0 kernel/locking/rwsem-xadd.c:617
Read of size 8 at addr ffff888082b76ad0 by task syz-executor.0/8725

CPU: 1 PID: 8725 Comm: syz-executor.0 Not tainted 4.14.196-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
Call Trace:
 __dump_stack lib/dump_stack.c:17 [inline]
 dump_stack+0x1b2/0x283 lib/dump_stack.c:58
 print_address_description.cold+0x54/0x1d3 mm/kasan/report.c:252
 kasan_report_error.cold+0x8a/0x194 mm/kasan/report.c:351
 kasan_report mm/kasan/report.c:409 [inline]
 __asan_report_load8_noabort+0x68/0x70 mm/kasan/report.c:430
 __read_once_size include/linux/compiler.h:183 [inline]
 atomic64_read arch/x86/include/asm/atomic64_64.h:22 [inline]
 atomic_long_read include/asm-generic/atomic-long.h:45 [inline]
 __rwsem_down_write_failed_common kernel/locking/rwsem-xadd.c:590 [inline]
 rwsem_down_write_failed+0x5d7/0x6d0 kernel/locking/rwsem-xadd.c:617
 call_rwsem_down_write_failed+0x13/0x20 arch/x86/lib/rwsem.S:105
 __down_write arch/x86/include/asm/rwsem.h:126 [inline]
 down_write+0x4f/0x90 kernel/locking/rwsem.c:56
 inode_lock include/linux/fs.h:719 [inline]
 __sock_release+0x86/0x2b0 net/socket.c:601
 sock_close+0x15/0x20 net/socket.c:1139
 __fput+0x25f/0x7a0 fs/file_table.c:210
 task_work_run+0x11f/0x190 kernel/task_work.c:113
 tracehook_notify_resume include/linux/tracehook.h:191 [inline]
 exit_to_usermode_loop+0x1ad/0x200 arch/x86/entry/common.c:164
 prepare_exit_to_usermode arch/x86/entry/common.c:199 [inline]
 syscall_return_slowpath arch/x86/entry/common.c:270 [inline]
 do_syscall_64+0x4a3/0x640 arch/x86/entry/common.c:297
 entry_SYSCALL_64_after_hwframe+0x46/0xbb
RIP: 0033:0x45d5b9
RSP: 002b:00007ff130f6fc78 EFLAGS: 00000246 ORIG_RAX: 00000000000000e9
RAX: 0000000000000000 RBX: 0000000000002ac0 RCX: 000000000045d5b9
RDX: 0000000000000005 RSI: 0000000000000001 RDI: 0000000000000004
RBP: 000000000118cf88 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000020000080 R11: 0000000000000246 R12: 000000000118cf4c
R13: 00007ffed61d28ef R14: 00007ff130f709c0 R15: 000000000118cf4c

Allocated by task 8725:
 save_stack mm/kasan/kasan.c:447 [inline]
 set_track mm/kasan/kasan.c:459 [inline]
 kasan_kmalloc+0xeb/0x160 mm/kasan/kasan.c:551
 kmem_cache_alloc+0x124/0x3c0 mm/slab.c:3552
 sock_alloc_inode+0x19/0x250 net/socket.c:251
 alloc_inode+0x5d/0x170 fs/inode.c:210
 new_inode_pseudo+0x14/0xe0 fs/inode.c:899
 sock_alloc+0x3c/0x270 net/socket.c:569
 __sock_create+0x8a/0x620 net/socket.c:1239
 sock_create net/socket.c:1315 [inline]
 SYSC_socket net/socket.c:1345 [inline]
 SyS_socket+0xd1/0x1b0 net/socket.c:1325
 do_syscall_64+0x1d5/0x640 arch/x86/entry/common.c:292
 entry_SYSCALL_64_after_hwframe+0x46/0xbb

Freed by task 8717:
 save_stack mm/kasan/kasan.c:447 [inline]
 set_track mm/kasan/kasan.c:459 [inline]
 kasan_slab_free+0xc3/0x1a0 mm/kasan/kasan.c:524
 __cache_free mm/slab.c:3496 [inline]
 kmem_cache_free+0x7c/0x2b0 mm/slab.c:3758
 destroy_inode+0xb9/0x110 fs/inode.c:267
 iput_final fs/inode.c:1524 [inline]
 iput+0x458/0x7e0 fs/inode.c:1551
 dentry_unlink_inode+0x25c/0x310 fs/dcache.c:387
 __dentry_kill+0x320/0x550 fs/dcache.c:591
 dentry_kill fs/dcache.c:632 [inline]
 dput.part.0+0x56f/0x710 fs/dcache.c:847
 dput+0x1b/0x30 fs/dcache.c:811
 __fput+0x445/0x7a0 fs/file_table.c:228
 task_work_run+0x11f/0x190 kernel/task_work.c:113
 tracehook_notify_resume include/linux/tracehook.h:191 [inline]
 exit_to_usermode_loop+0x1ad/0x200 arch/x86/entry/common.c:164
 prepare_exit_to_usermode arch/x86/entry/common.c:199 [inline]
 syscall_return_slowpath arch/x86/entry/common.c:270 [inline]
 do_syscall_64+0x4a3/0x640 arch/x86/entry/common.c:297
 entry_SYSCALL_64_after_hwframe+0x46/0xbb

The buggy address belongs to the object at ffff888082b769c0
 which belongs to the cache sock_inode_cache of size 1000
The buggy address is located 272 bytes inside of
 1000-byte region [ffff888082b769c0, ffff888082b76da8)
The buggy address belongs to the page:
page:ffffea00020add80 count:1 mapcount:0 mapping:ffff888082b760c0 index:0xffff888082b76ffd
flags: 0xfffe0000000100(slab)
raw: 00fffe0000000100 ffff888082b760c0 ffff888082b76ffd 0000000100000003
raw: ffffea00020ae2a0 ffffea00020adde0 ffff8880a99bd900 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
 ffff888082b76980: fc fc fc fc fc fc fc fc fb fb fb fb fb fb fb fb
 ffff888082b76a00: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>ffff888082b76a80: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
                                                 ^
 ffff888082b76b00: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff888082b76b80: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
==================================================================

Crashes (3):
Manager Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Title
ci2-linux-4-14 2020/09/04 05:14 linux-4.14.y 2f166cdcf8a9 abf9ba4f .config log report syz
ci2-linux-4-14 2020/09/01 10:07 linux-4.14.y d7e78d08fa77 d5a3ae1f .config log report syz
ci2-linux-4-14 2020/08/27 04:12 linux-4.14.y d7e78d08fa77 318430cb .config log report