syzbot


WARNING: suspicious RCU usage in __clear_user

Status: fixed on 2021/11/10 00:50
Reported-by: syzbot+@syzkaller.appspotmail.com
Fix commit: 3066820034b5 rcu: Reject RCU_LOCKDEP_WARN() false positives
First crash: 614d, last: 614d

Sample crash report:
=============================
WARNING: suspicious RCU usage
5.13.0-rc3-syzkaller #0 Not tainted
-----------------------------
kernel/sched/core.c:8304 Illegal context switch in RCU-bh read-side critical section!

other info that might help us debug this:


rcu_scheduler_active = 2, debug_locks = 0
1 lock held by syz-executor.1/8484:
 #0: 
ffff888027c1cd88
 (
&xt[i].mutex
){+.+.}-{3:3}
, at: xt_find_table_lock+0x18d/0xae0 net/netfilter/x_tables.c:1226

stack backtrace:
CPU: 1 PID: 8484 Comm: syz-executor.1 Not tainted 5.13.0-rc3-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
Call Trace:
 __dump_stack lib/dump_stack.c:79 [inline]
 dump_stack+0x141/0x1d7 lib/dump_stack.c:120
 ___might_sleep+0x229/0x2c0 kernel/sched/core.c:8304
 __might_fault+0x6e/0x180 mm/memory.c:5067
 __clear_user+0x1e/0x70 arch/x86/lib/usercopy_64.c:20
 clear_user+0xd3/0x110 arch/x86/lib/usercopy_64.c:54
 xt_data_to_user+0xbb/0xf0 net/netfilter/x_tables.c:305
 xt_target_to_user net/netfilter/x_tables.c:330 [inline]
 xt_target_to_user+0x165/0x200 net/netfilter/x_tables.c:326
 copy_entries_to_user net/ipv6/netfilter/ip6_tables.c:876 [inline]
 get_entries net/ipv6/netfilter/ip6_tables.c:1040 [inline]
 do_ip6t_get_ctl+0x852/0xa10 net/ipv6/netfilter/ip6_tables.c:1671
 nf_getsockopt+0x72/0xd0 net/netfilter/nf_sockopt.c:116
 ipv6_getsockopt+0x1be/0x270 net/ipv6/ipv6_sockglue.c:1486
 tcp_getsockopt+0x86/0xd0 net/ipv4/tcp.c:4252
 __sys_getsockopt+0x21f/0x5f0 net/socket.c:2161
 __do_sys_getsockopt net/socket.c:2176 [inline]
 __se_sys_getsockopt net/socket.c:2173 [inline]
 __x64_sys_getsockopt+0xba/0x150 net/socket.c:2173
 do_syscall_64+0x3a/0xb0 arch/x86/entry/common.c:47
 entry_SYSCALL_64_after_hwframe+0x44/0xae
RIP: 0033:0x467bea
Code: 48 c7 c1 bc ff ff ff f7 d8 64 89 01 48 83 c8 ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 44 00 00 49 89 ca b8 37 00 00 00 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 c7 c1 bc ff ff ff f7 d8 64 89 01 48
RSP: 002b:0000000000a9f678 EFLAGS: 00000212 ORIG_RAX: 0000000000000037
RAX: ffffffffffffffda RBX: 0000000000000029 RCX: 0000000000467bea
RDX: 0000000000000041 RSI: 0000000000000029 RDI: 0000000000000003
RBP: 0000000000a9f6a0 R08: 0000000000a9f69c R09: 0079746972756365
R10: 0000000000a9f700 R11: 0000000000000212 R12: 0000000000a9f700
R13: 0000000000000003 R14: 0000000000a9f69c R15: 0000000000542b40

Crashes (1):
Manager Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets Title
ci-upstream-kasan-gce 2021/05/25 16:04 upstream a050a6d2b7e8 3c7fef33 .config console log report info WARNING: suspicious RCU usage in __clear_user
* Struck through repros no longer work on HEAD.