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Date: Sun, 05 Apr 2015 23:59:52 -0400
From: Sasha Levin <sasha.levin@...cle.com>
To: LKML <linux-kernel@...r.kernel.org>
CC: Rusty Russell <rusty@...tcorp.com.au>,
Dave Jones <davej@...hat.com>, Michal Hocko <mhocko@...e.cz>,
Borislav Petkov <bp@...en8.de>,
Linus Torvalds <torvalds@...ux-foundation.org>
Subject: Hang on large copy_from_user with PREEMPT_NONE
Hi all,
I'm seeing an interesting hang when trinity is trying to load a large module, where
the size passed by userspace is larger than the amount of memory actually allocated
in userspace and passed in the 'from' parameter:
[ 1549.080032] NMI watchdog: BUG: soft lockup - CPU#11 stuck for 22s! [trinity-c11:12699]
[ 1549.080032] Modules linked in:
[ 1549.080032] hardirqs last enabled at (4202427): restore_args (arch/x86/kernel/entry_64.S:750)
[ 1549.080032] hardirqs last disabled at (4202428): apic_timer_interrupt (arch/x86/kernel/entry_64.S:890)
[ 1549.080032] softirqs last enabled at (4202426): __do_softirq (./arch/x86/include/asm/preempt.h:22 kernel/softirq.c:300)
[ 1549.080032] softirqs last disabled at (4202421): irq_exit (kernel/softirq.c:350 kernel/softirq.c:391)
[ 1549.080032] CPU: 11 PID: 12699 Comm: trinity-c11 Not tainted 4.0.0-rc6-next-20150402-sasha-00039-ge0bdae3-dirty #2125
[ 1549.080032] task: ffff880260f30000 ti: ffff88025ebe8000 task.ti: ffff88025ebe8000
[ 1549.080032] RIP: copy_user_handle_tail (arch/x86/lib/usercopy_64.c:85)
[ 1549.080032] RSP: 0000:ffff88025ebefe38 EFLAGS: 00010202
[ 1549.080032] RAX: 00000000356cb494 RBX: 1ffff1004bd7dfcb RCX: 0000000000000000
[ 1549.080032] RDX: 000000009277d652 RSI: ffffc90078bba001 RDI: ffffc90078bba000
[ 1549.080032] RBP: ffff88025ebefe38 R08: 0000000000000000 R09: 0000000002f75001
[ 1549.080032] R10: 0000000000000000 R11: 0000000000000000 R12: ffff88025ebefe78
[ 1549.080032] R13: ffff88025ebeff18 R14: 0000000094949494 R15: 0000000000da91be
[ 1549.080032] FS: 00007f1f669df700(0000) GS:ffff8803f2800000(0000) knlGS:0000000000000000
[ 1549.080032] CS: 0010 DS: 0000 ES: 0000 CR0: 000000008005003b
[ 1549.080032] CR2: 0000000002f75000 CR3: 000000025d031000 CR4: 00000000000007a0
[ 1549.080032] Stack:
[ 1549.080032] ffff88025ebeff48 ffffffff963c5ef0 ffffc9001993c000 0000000000da91be
[ 1549.080032] 0000000041b58ab3 ffffffffa32918f3 ffffffff963c5da0 0000000000000286
[ 1549.080032] ffffc9001993c000 0000000094949494 0000000000000000 0000000000000000
[ 1549.080032] Call Trace:
[ 1549.080032] SyS_init_module (kernel/module.c:2505 kernel/module.c:3401 kernel/module.c:3388)
[ 1549.080032] ? load_module (kernel/module.c:3388)
[ 1549.080032] ia32_do_call (arch/x86/ia32/ia32entry.S:501)
[ 1549.080032] Code: d0 66 66 90 8a 06 66 66 90 45 85 c0 74 d3 85 c9 74 23 89 d0 45 31 c0 eb 08 83 e8 01 48 89 f7 74 14 48 8d 77 01 44 89 c1 66 66 90 <c6> 07 00 66 66 90 85 c9 74 e4 89 d0 66 66 90 5d c3 0f 1f 44 00
All code
========
0: d0 66 66 shlb 0x66(%rsi)
3: 90 nop
4: 8a 06 mov (%rsi),%al
6: 66 66 90 data32 xchg %ax,%ax
9: 45 85 c0 test %r8d,%r8d
c: 74 d3 je 0xffffffffffffffe1
e: 85 c9 test %ecx,%ecx
10: 74 23 je 0x35
12: 89 d0 mov %edx,%eax
14: 45 31 c0 xor %r8d,%r8d
17: eb 08 jmp 0x21
19: 83 e8 01 sub $0x1,%eax
1c: 48 89 f7 mov %rsi,%rdi
1f: 74 14 je 0x35
21: 48 8d 77 01 lea 0x1(%rdi),%rsi
25: 44 89 c1 mov %r8d,%ecx
28: 66 66 90 data32 xchg %ax,%ax
2b:* c6 07 00 movb $0x0,(%rdi) <-- trapping instruction
2e: 66 66 90 data32 xchg %ax,%ax
31: 85 c9 test %ecx,%ecx
33: 74 e4 je 0x19
35: 89 d0 mov %edx,%eax
37: 66 66 90 data32 xchg %ax,%ax
3a: 5d pop %rbp
3b: c3 retq
3c: 0f 1f 44 00 00 nopl 0x0(%rax,%rax,1)
Code starting with the faulting instruction
===========================================
0: c6 07 00 movb $0x0,(%rdi)
3: 66 66 90 data32 xchg %ax,%ax
6: 85 c9 test %ecx,%ecx
8: 74 e4 je 0xffffffffffffffee
a: 89 d0 mov %edx,%eax
c: 66 66 90 data32 xchg %ax,%ax
f: 5d pop %rbp
10: c3 retq
11: 0f 1f 44 00 00 nopl 0x0(%rax,%rax,1)
This is the result of getting copy_user_handle_tail to zero out a large block of
kernel memory very inefficiently:
for (c = 0, zero_len = len; zerorest && zero_len; --zero_len)
if (__put_user_nocheck(c, to++, sizeof(char)))
break;
Thanks,
Sasha
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