Re: BUG: unable to handle kernel paging request

Linus Torvalds
2011-03-27T15:37:57Z

Al, this smells like your /proc cleanups/fixes...

On Sun, Mar 27, 2011 at 2:16 AM, Anca Emanuel <anca.emanuel@gmail.com> wrote:
> Hi, I'm using latest kernel git.
>
>
> [15117.080119] BUG: unable to handle kernel paging request at fffffffffffffff3

That's "-13" (possibly -EACCES)

> [15117.080152] IP: [<ffffffff811b4989>] vma_stop+0x19/0x40

.. and the code disassembles to

0: 55 push %rbp
1: 48 89 e5 mov %rsp,%rbp
4: 53 push %rbx
5: 48 83 ec 08 sub $0x8,%rsp
9: 0f 1f 44 00 00 nopl 0x0(%rax,%rax,1)
e: 48 85 f6 test %rsi,%rsi
11: 74 1a je 0x2d
13: 48 39 77 10 cmp %rsi,0x10(%rdi)
17: 74 14 je 0x2d
19: 8b 1e mov (%rsi),%ebx
1b: 48 8d 7b 60 lea 0x60(%rbx),%rdi
1f: e8 eb 2f ed ff callq up_read

where that instruction at 0x19 is the access "mm = vma->vm_mm". So
it's vma that is -EPERM.

I bet it's due to commit ec6fd8a4355c ("report errors in /proc/*/*map*
sanely"), which replaces NULL with various ERR_PTR() cases.

> [15117.080660] Call Trace:
> [15117.080671]  [<ffffffff811b4a3a>] m_stop+0x1a/0x40
> [15117.080685]  [<ffffffff8117d991>] seq_read+0x1e1/0x420
> [15117.080698]  [<ffffffff8115c685>] vfs_read+0xc5/0x190
> [15117.080711]  [<ffffffff8115c851>] sys_read+0x51/0x90
> [15117.080724]  [<ffffffff815b2d02>] system_call_fastpath+0x16/0x1b

Al?

Linus