Hi all,
While fuzzing with trinity running inside a KVM tools guest using latest -next kernel,
I've stumbled on a "mm: BUG: Bad rss-counter state" error which was pretty non-obvious
in the mix of the kernel spew (why?).
I've added a small BUG() after the printk() in check_mm(), and here's the full output:
[ 318.334905] BUG: Bad rss-counter state mm:ffff8801e6dec000 idx:0 val:1
[ 318.335955] ------------[ cut here ]------------
[ 318.336507] kernel BUG at kernel/fork.c:562!
[ 318.336930] invalid opcode: 0000 [#1] PREEMPT SMP DEBUG_PAGEALLOC
[ 318.337826] Dumping ftrace buffer:
[ 318.338431] (ftrace buffer empty)
[ 318.338951] Modules linked in:
[ 318.339287] CPU: 45 PID: 10022 Comm: trinity-c190 Tainted: G W 3.13.0-next
-20140122-sasha-00011-gcc8342a-dirty #4
[ 318.340120] task: ffff8801e6a9b000 ti: ffff8801e6aee000 task.ti: ffff8801e6aee000
[ 318.340120] RIP: 0010:[<ffffffff8113ca4a>] [<ffffffff8113ca4a>] __mmdrop+0x9a/0xc0
[ 318.340120] RSP: 0000:ffff8801e6aefe68 EFLAGS: 00010292
[ 318.340120] RAX: 000000000000003a RBX: ffff8801e6dec000 RCX: 0000000000000001
[ 318.340120] RDX: 0000000000000000 RSI: 0000000000000001 RDI: 0000000000000286
[ 318.340120] RBP: ffff8801e6aefe78 R08: 0000000000000001 R09: 0000000000000000
[ 318.340120] R10: 0000000000000001 R11: 0000000000000001 R12: ffff8801e6dec138
[ 318.340120] R13: ffff8801e6dec000 R14: ffff8801e6dec0a8 R15: 00000000000000a3
[ 318.340120] FS: 00007f6bc5915700(0000) GS:ffff88007b400000(0000) knlGS:000000000000
0000
[ 318.340120] CS: 0010 DS: 0000 ES: 0000 CR0: 000000008005003b
[ 318.340120] CR2: 00007fffd3d62588 CR3: 0000000005e26000 CR4: 00000000000006e0
[ 318.340120] Stack:
[ 318.340120] ffff8801e6dec138 ffff8801e6dec000 ffff8801e6aefe98 ffffffff8113cb3b
[ 318.340120] ffff8801e6a9bbb0 ffff8801e6a9b000 ffff8801e6aefef8 ffffffff81140ced
[ 318.340120] ffff8801e6c4db00 ffff8801e6c4db00 ffff8801e6aefef8 ffffffff811f3ea5
[ 318.340120] Call Trace:
[ 318.340120] [<ffffffff8113cb3b>] mmput+0xcb/0xe0
[ 318.340120] [<ffffffff81140ced>] exit_mm+0x18d/0x1a0
[ 318.340120] [<ffffffff811f3ea5>] ? acct_collect+0x175/0x1b0
[ 318.340120] [<ffffffff8114315f>] do_exit+0x26f/0x520
[ 318.355754] [<ffffffff811434b9>] do_group_exit+0xa9/0xe0
[ 318.355754] [<ffffffff81143507>] SyS_exit_group+0x17/0x20
[ 318.355754] [<ffffffff8444b7d0>] tracesys+0xdd/0xe2
[ 318.355754] Code: 00 00 eb 16 0f 1f 44 00 00 48 8b 8b 68 03 00 00 48 85 c9 74 24 ba 02 00 00 00
48 89 de 48 c7 c7 10 16 68 85 31 c0 e8 a2 d2 2f 03 <0f> 0b 0f 1f 40 00 eb fe 66 0f 1f 44 00 00 48 89
de 48 8b 3d 1e
[ 318.355754] RIP [<ffffffff8113ca4a>] __mmdrop+0x9a/0xc0
[ 318.355754] RSP <ffff8801e6aefe68>
[ 318.363991] ---[ end trace 7d85aceb881be62b ]---
Thanks,
Sasha
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