On Fri, 9 Sep 2005, Ian Collier wrote:
> On Fri, Sep 09, 2005 at 08:32:10AM -0400, linux-os (Dick Johnson) wrote:
>> 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().
>
> Well, I didn't write the code (it's right there in drivers/block/loop.c
> in 2.6.13) and I can't see where there's a spin-lock. In fact it does
> use a semaphore.
>
> imc
> -
Try to see if it is really the loop device or something that is
interfacing with it. Here I copy the contents of a DOS floppy
to a file, then mount the file through the loop device:
Script started on Fri 09 Sep 2005 10:17:27 AM EDT
[EMAIL PROTECTED] driver]# cp /dev/fd0 image
[EMAIL PROTECTED] driver]# ls -la image
-rw-r----- 1 root root 1474560 Sep 9 10:18 image
[EMAIL PROTECTED] driver]# mount -o loop image /mnt
[EMAIL PROTECTED] driver]# ls -la /mnt
total 894
drwxr-xr-x 2 root root 7168 Dec 31 1969 [01;34m.[00m
drwxr-xr-x 26 root root 4096 Sep 9 08:41 [01;34m..[00m
-rwxr-xr-x 1 root root 170 Apr 10 2003 [01;32mautoexec.bat[00m
-rwxr-xr-x 1 root root 86413 Jul 30 2002 [01;32mcommand.com[00m
-rwxr-xr-x 1 root root 2882 Apr 9 2003 [01;32mconfig.sys[00m
-rwxr-xr-x 1 root root 16967 Mar 27 2003 [01;32merr_lev.bat[00m
-rwxr-xr-x 1 root root 5874 Jan 21 2002 [01;32mfdxxms.sys[00m
-rwxr-xr-x 1 root root 3173 Mar 27 2003 [01;32mfindramd.exe[00m
-rwxr-xr-x 1 root root 41293 Aug 4 2002 [01;32mkernel.sys[00m
-rwxr-xr-x 1 root root 719592 Jun 28 2004 [01;32msw.exe[00m
-rwxr-xr-x 1 root root 25084 Sep 28 2000 [01;32mtdsk.exe[00m
[EMAIL PROTECTED] driver]# umount /mnt
[EMAIL PROTECTED] driver]# exit
Script done on Fri 09 Sep 2005 10:18:55 AM EDT
This seems to work okay in 2.6.13, however I don't think it
__should__ work because in lo_ioctl(), the following
functions reference 'arg' without using copy/to/from/user() or
put/get/user():
loop_set_fd (vi fget()),
loop_change_fd (via fget()),
loop_get_status (via memset() and others),
loop_get_status_old,
loop_set_status64,
loop_get_status64,
... etc.
Basically, anything that uses ioctl() on the loop device may find
that they crash the system. This code is broken.
Anton Altaparmakov last 'touched' that code in Feb 2005. Maybe
he can fix the ioctl procedure to use the correct interface to
user-land????
Cheers,
Dick Johnson
Penguin : Linux version 2.6.13 on an i686 machine (5589.53 BogoMips).
Warning : 98.36% of all statistics are fiction.
.
I apologize for the following. I tried to kill it with the above dot :
****************************************************************
The information transmitted in this message is confidential and may be
privileged. Any review, retransmission, dissemination, or other use of this
information by persons or entities other than the intended recipient is
prohibited. If you are not the intended recipient, please notify Analogic
Corporation immediately - by replying to this message or by sending an email to
[EMAIL PROTECTED] - and destroy all copies of this information, including any
attachments, without reading or disclosing them.
Thank you.
-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to [EMAIL PROTECTED]
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/
