Re: pciconf -lv - /dev/pci error

From: Robert Watson (rwatson_at_freebsd.org)
Date: 12/31/03

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    Date: Wed, 31 Dec 2003 13:01:06 -0500 (EST)
To: William Michael Grim <wgrim@siue.edu>

    On Wed, 31 Dec 2003, William Michael Grim wrote:

    > I have 5.1-RELEASE installed on my system, and I've never needed to do a
    > "pciconf -lv" to probe the system before. However, I tried doing it
    > earlier today after logging in through SSH and doing "su -" to become
    > superuser. I received this error:
    >
    > [root@snow 09:12:42 root]# pciconf -lv
    > pciconf: /dev/pci: Operation not permitted
    >
    > [root@snow 09:15:41 root]# ls -l /dev/pci
    > crw-r--r-- 1 root wheel 251, 0 Nov 2 05:09 /dev/pci
    >
    > So, as you can see, the permissions are correct. Perhaps I don't have
    > something compiled into my kernel? I can attach a dmesg and kernel
    > config if it's necessary.

    pciconf -lv appears to cause pciconf to open /dev/pci writable:

       731 pciconf CALL open(0x8049a55,0x2,0)
       731 pciconf NAMI "/dev/pci"
       731 pciconf RET open -1 errno 13 Permission denied

    And, of course, it's not writable by non-root. The attached patch causes
    pciconf to open /dev/pci read-only when listing devices (apply to
    usr.sbin/pciconf/pciconf.c):

    Index: pciconf.c
    ===================================================================
    RCS file: /home/ncvs/src/usr.sbin/pciconf/pciconf.c,v
    retrieving revision 1.19
    diff -u -r1.19 pciconf.c
    --- pciconf.c 20 Jun 2003 23:59:25 -0000 1.19
    +++ pciconf.c 31 Dec 2003 17:58:45 -0000
    @@ -165,7 +165,7 @@
             if (verbose)
                     load_vendors();
     
    - fd = open(_PATH_DEVPCI, O_RDWR, 0);
    + fd = open(_PATH_DEVPCI, O_RDONLY, 0);
             if (fd < 0)
                     err(1, "%s", _PATH_DEVPCI);
     

    The pci_user.c code in the kernel requires that the caller hold a writable
    file descriptor for most of the ioctls; the exception is PCIOCGETCONF,
    which is the only ioctl pciconf's list_devs() uses. We can probably just
    go ahead and commit this patch, I think. The reason a check was added to
    the kernel pci ioctl code is that unaligned writes to /dev/pci can cause
    faults, I believe...

    Robert N M Watson FreeBSD Core Team, TrustedBSD Projects
    robert@fledge.watson.org Senior Research Scientist, McAfee Research

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