Re: Bug#274860: Acknowledgement (kernel-image-2.6.8-1-686: CDROM_SEND_PACKET ioctls only work as root)

From: Luke Kenneth Casson Leighton (lkcl_at_lkcl.net)
Date: 10/04/04

  • Next message: Paul Jackson: "Re: Too many __s in donauboe.h" 
    Date:	Mon, 4 Oct 2004 14:53:26 +0100
To: 274860@bugs.debian.org

    found it.

    it's a new piece of kernel code verify_command in
    drivers/block/scsi_ioctl.c, which checks for the capability
    CAP_SYS_RAWIO.

    ah, dammit.

    for k3b to work, you'd have to install it setuid root, call
    getcap(), remove all but the necessary capabilities (i.e. don't
    remove CAP_SYS_RAWIO), do a setfsuid() and setfsgid() and do
    a setcap().

    fuse (file system in userspace) uses this technique for allowing
    mount and unmount but nothing else

    [which doesn't work on 2.6.8 btw: the getcap() fails, but i did notice
    that debian doesn't install fusermount as setuid to root which is half
    the problem...]

    l.

    On Mon, Oct 04, 2004 at 02:10:14PM +0100, Luke Kenneth Casson Leighton wrote:
    > additional info:
    >
    > kernel 2.6.8. ioctl ("/dev/hdc", CDROM_SEND_PACKET, cmd)
    >
    > commands that are failing as non-root, even when permission is granted
    > rwxrwxrwx to /dev/hdc, are, according to some debug info added to k3b:
    >
    > GET CONFIGURATION (46)
    > error code: 0
    > sense key: NO SENSE (2)
    > asc: 0
    > ascq: 0
    >
    > and:
    >
    > MODE SELECT (55)
    > error code: 0
    > sense key: NO SENSE (2)
    > asc: 0
    > ascq: 0
    >
    > the result is that k3b cannot determine that the drive exists, therefore
    > it cannot use it even though cdrecord might actually work.
    >
    >
    > as root, the following errors occur:
    >
    > MODE SELECT (46)
    > errorcode: 70
    > sense key: ILLEGAL REQUEST (5)
    > asc: 26
    > ascq: 0
    >
    > READ DVD STRUCTURE (ad)
    > errorcode: 70
    > sense key: NOT READY (2)
    > asc: 3a
    > ascq: 0
    >
    > presumably it can be concluded that the GET CONFIGURATION ioctl command
    > is the one at fault.
    >
    > ... what gives?
    >
    > l.
    >
    > --
    > --
    > Truth, honesty and respect are rare commodities that all spring from
    > the same well: Love. If you love yourself and everyone and everything
    > around you, funnily and coincidentally enough, life gets a lot better.
    > --
    > lkcl.net <br />
    > <a href="mailto:lkcl@lkcl.net"> lkcl@lkcl.net </a> <br />
    >
    > --
    > --
    > Truth, honesty and respect are rare commodities that all spring from
    > the same well: Love. If you love yourself and everyone and everything
    > around you, funnily and coincidentally enough, life gets a lot better.
    > --
    > lkcl.net <br />
    > <a href="mailto:lkcl@lkcl.net"> lkcl@lkcl.net </a> <br />
    > 

    -- 
--
Truth, honesty and respect are rare commodities that all spring from
the same well: Love.  If you love yourself and everyone and everything
around you, funnily and coincidentally enough, life gets a lot better.
--
<a href="http://lkcl.net">      lkcl.net      </a> <br />
<a href="mailto:lkcl@lkcl.net"> lkcl@lkcl.net </a> <br />
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