[libvirt] [PATCH] util: Don't try to fchown files opened as non-root

Eric Blake eblake at redhat.com
Fri Jul 8 13:46:06 UTC 2011

On 07/08/2011 07:30 AM, Jiri Denemark wrote:
> When virFileOpenAs is called with VIR_FILE_OPEN_AS_UID flag and uid/gid
> different from root/root while libvirtd is running as root, we fork a
> new child, change its effective UID/GID to uid/gid and run
> virFileOpenAsNoFork. It doesn't make any sense to fchown() the opened
> file in this case since we already know that uid/gid can access the file
> when open succeeds and one of the following situations may happen:
> - the file is already owned by uid/gid and we skip fchown even before
>   this patch
> - the file is owned by uid but not gid because it was created in a
>   directory with SETGID set, in which case it is desirable not to change
>   the group
> - the file may be owned by a completely different user and/or group
>   because it was created on a root-squashed or even all-squashed NFS
>   filesystem, in which case fchown would most likely fail anyway
> ---
>  src/util/util.c |   31 +++++++++++++++++++------------
>  1 files changed, 19 insertions(+), 12 deletions(-)


> +    /* VIR_FILE_OPEN_AS_UID in flags means we are running in a child process
> +     * owned by uid and gid */
> +    if (!(flags & VIR_FILE_OPEN_AS_UID)) {
> +        struct stat st;
> +        if (fstat(fd, &st) == -1) {

Style nit - add a newline between the declaration of st and the first
statement (the nested if).

Eric Blake   eblake at redhat.com    +1-801-349-2682
Libvirt virtualization library http://libvirt.org

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