Re: Question regarding BUG in mm/slub.c

[Pekka Enberg]

On Wed, Nov 11, 2009 at 9:34 PM, Larry Finger <Larry.Finger@xxxxxxxxxxxx> wrote:
> One of the users of a BCM4312 device hit the BUG in the mm/slub.c version of
> kfree in the following code fragment:
>
>        page = virt_to_head_page(x);
>        if (unlikely(!PageSlab(page))) {
>                BUG_ON(!PageCompound(page));
>                kmemleak_free(x);
>                put_page(page);
>                return;
>        }
>
> What is the meaning of PageCompound(page) being zero?

You're passing a pointer to kfree() that did not come from kmalloc().
If a page is not PageSlab(), it needs to be a compound page if it came
from the page allocator pass-through.

> For completeness, the system log output is:
>
> Nov 11 14:31:31 doughnut ntpd[398]: kernel time sync status change 2001
> Nov 11 14:36:57 doughnut ntpd[398]: synchronized to 130.88.200.4, stratum 2
> Nov 11 14:37:31 doughnut kernel: ------------[ cut here ]------------
> Nov 11 14:37:31 doughnut kernel: kernel BUG at mm/slub.c:2969!
> Nov 11 14:37:31 doughnut kernel: invalid opcode: 0000 [#1] SMP
> Nov 11 14:37:31 doughnut kernel: last sysfs file:
> /sys/devices/pci0000:00/0000:00:02.1/resource
> Nov 11 14:37:31 doughnut kernel: Modules linked in:
> Nov 11 14:37:31 doughnut kernel:
> Nov 11 14:37:31 doughnut kernel: Pid: 343, comm: irq/17-b43 Not tainted
> (2.6.32-rc6-wl #1) Inspiron 910
> Nov 11 14:37:31 doughnut kernel: EIP: 0060:[<c107a5b9>] EFLAGS: 00010246 CPU: 0
> Nov 11 14:37:31 doughnut kernel: EIP is at kfree+0xa9/0xb0
> Nov 11 14:37:31 doughnut kernel: EAX: dededede EBX: f68f8200 ECX: 40000000 EDX:
> c19b9da0
> Nov 11 14:37:31 doughnut kernel: ESI: ef000000 EDI: 00000400 EBP: f72c5400 ESP:
> f6a3ded0
> Nov 11 14:37:31 doughnut kernel:  DS: 007b ES: 007b FS: 00d8 GS: 00e0 SS: 0068
> Nov 11 14:37:31 doughnut kernel: Process irq/17-b43 (pid: 343, ti=f6a3c000
> task=f73fa380 task.ti=f6a3c000)
> Nov 11 14:37:31 doughnut kernel: Stack:
> Nov 11 14:37:31 doughnut kernel:  000e7ef0 c1021c31 f68f8200 ef000000 00000400
> c12d47ce c13ee7c0 f73fa380
> Nov 11 14:37:31 doughnut kernel: <0> 7fff7fff dededede 00000000 c141c934
> f7093458 f6a3df64 f73b7000 f72c5400
> Nov 11 14:37:31 doughnut kernel: <0> f72c5400 f6a3df64 00000000 c12d0556
> 00000000 c12c0b77 00000046 00000046
> Nov 11 14:37:31 doughnut kernel: Call Trace:
> Nov 11 14:37:31 doughnut kernel:  [<c1021c31>] ? update_curr_rt+0x251/0x2c0
> Nov 11 14:37:31 doughnut kernel:  [<c12d47ce>] ? b43_dma_handle_txstatus+0xbe/0x270
> Nov 11 14:37:31 doughnut kernel:  [<c12d0556>] ? b43_handle_txstatus+0x36/0x60
> Nov 11 14:37:31 doughnut kernel:  [<c12c0b77>] ? b43_do_interrupt_thread+0x1d7/0x5d0
> Nov 11 14:37:31 doughnut kernel:  [<c12c0f85>] ?
> b43_interrupt_thread_handler+0x15/0x30
> Nov 11 14:37:31 doughnut kernel:  [<c1050a94>] ? irq_thread+0x104/0x1d0
> Nov 11 14:37:31 doughnut kernel:  [<c101d320>] ? complete+0x40/0x60
> Nov 11 14:37:31 doughnut kernel:  [<c1050990>] ? irq_thread+0x0/0x1d0
> Nov 11 14:37:31 doughnut kernel:  [<c1039c64>] ? kthread+0x74/0x80
> Nov 11 14:37:31 doughnut kernel:  [<c1039bf0>] ? kthread+0x0/0x80
> Nov 11 14:37:31 doughnut kernel:  [<c10038cf>] ? kernel_thread_helper+0x7/0x18
> Nov 11 14:37:31 doughnut kernel: Code: e8 1d fc ff ff eb d9 66 f7 c1 00 c0 74 1d
> 8b 5c 24 08 89 d0 8b 74 24 0c 8b 7c 24 10 83 c4 14 e9 8e 24 fe ff 8b 52 0c 8b 0a
> eb 84 <0f> 0b eb fe 8d 76 00 83 e8 60 e9 48 ff ff ff 90 8d b4 26 00 00
> Nov 11 14:37:31 doughnut kernel: EIP: [<c107a5b9>] kfree+0xa9/0xb0 SS:ESP
> 0068:f6a3ded0
> Nov 11 14:37:31 doughnut kernel: ---[ end trace 021257f2296ca88f ]---
> Nov 11 14:37:31 doughnut kernel: exiting task "irq/17-b43" (343) is an active
> IRQ thread (irq 17)
>
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