Re: 2.6.13: loop ioctl crashes

["linux-os \(Dick Johnson\)" <linux-os@analogic.com>]

On Fri, 9 Sep 2005, Ian Collier wrote:

> I'm trying out PPDD from https://retiisi.dyndns.org/~sailus/ppdd/
> because I have some old stuff in that format.  However, the crash
> seems to occur in code that isn't touched by the PPDD patch.  It
> happens while I'm trying to set up the loop device - I haven't got
> as far as actually using it yet.
>
> If I'm lucky then when I issue the losetup command and successfully
> type in the passphrase then losetup says something of the form
> ioctl: LOOP_SET_STATUS: Bad address
> and the kernel says:
>
> Debug: sleeping function called from invalid context at arch/i386/lib/usercopy.c:634
> in_atomic():1, irqs_disabled():0
>  [<c011f8eb>] __might_sleep+0xab/0xc0
>  [<c0211aa3>] copy_from_user+0x23/0x90
>  [<d0a9fe80>] loop_set_status_old+0x30/0x70 [loop]
>
> However, it often seems to panic in a variety of horrible ways while
> trying to print the above message.
>
> Clearly I have CONFIG_DEBUG_SPINLOCK_SLEEP set (as my config is
> based on Fedora's), and I suppose I could just try unsetting it to
> make the message go away.  That wouldn't make the underlying bug go
> away, though.  If it makes any difference, loop and all the crypto
> algorithms are compiled as modules.
>
> I don't understand why it's an invalid context.  I also don't understand
> why the traceback stops at loop_set_status_old given that it must have
> been called from lo_ioctl.  (But maybe the answer to the latter would
> explain the former.)
>
> I may try just moving the copy_from_user() out to the beginning of
> lo_ioctl and see what happens.  Any other suggestions?  In case it's
> not obvious by now, I'm not really a kernel hacker.
>
> imc

I guess you are trying to do a copy_from_user() with a spin-lock
being held or the interrupts otherwise disabled. You can hold
a semaphore, to prevent somebody else from interfering with
you, but you cannot hold a spin-lock during copy/to/from/user().


Cheers,
Dick Johnson
Penguin : Linux version 2.6.13 on an i686 machine (5589.54 BogoMips).
Warning : 98.36% of all statistics are fiction.
.
I apologize for the following. I tried to kill it with the above dot :

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