Re: [Xen-devel] [PATCH] xl: Return an error if an empty file is passed to cd-insert

[George Dunlap <george.dunlap@xxxxxxxxxxxxx>]

On 13/05/13 10:35, Roger Pau Monné wrote:
> On 10/05/13 17:43, George Dunlap wrote:
> > Two changes:
> > * Stat the file before calling libxl_cdrom_insert()
> > * Return an error if anything fails (including libxl_cdrom_insert)
> >
> > This is in part to work around the fact that the RAW disk type
> > is used for things that aren't actually files; so we can't call
> > stat in libxl_device.c:libxl__device_disk_set_backend() because
> > it may be going over a remote protocol.
> >
> > Signed-off-by: George Dunlap <george.dunlap@xxxxxxxxxxxxx>
> > CC: Ian Campbell <ian.campbell@xxxxxxxxxx>
> > CC: Ian Jackson <ian.jackson@xxxxxxxxxx>
> > ---
> >   tools/libxl/xl_cmdimpl.c |   26 +++++++++++++++++++++-----
> >   1 file changed, 21 insertions(+), 5 deletions(-)
> >
> > diff --git a/tools/libxl/xl_cmdimpl.c b/tools/libxl/xl_cmdimpl.c
> > index c1a969b..e8ce35b 100644
> > --- a/tools/libxl/xl_cmdimpl.c
> > +++ b/tools/libxl/xl_cmdimpl.c
> > @@ -2505,25 +2505,42 @@ int main_memset(int argc, char **argv)
> >       return 0;
> >   }
> >   
> > -static void cd_insert(uint32_t domid, const char *virtdev, char *phys)
> > +static int cd_insert(uint32_t domid, const char *virtdev, char *phys)
> >   {
> >       libxl_device_disk disk; /* we don't free disk's contents */
> >       char *buf = NULL;
> >       XLU_Config *config = 0;
> > +    struct stat b;
> > +    int rc = 0;
> >   
> >   
> >       if (asprintf(&buf, "vdev=%s,access=r,devtype=cdrom,target=%s",
> >                    virtdev, phys ? phys : "") < 0) {
> >           fprintf(stderr, "out of memory\n");
> > -        return;
> > +        return 1;
> ERROR_NOMEM
If this were a library function I would definitely return -ERROR_NOMEM; 
but since this is just a helper function whose value is going to be 
returned to the command-line, I think just returning 1 is the best thing 
to do.
> >       }
> >   
> >       parse_disk_config(&config, buf, &disk);
> >   
> > -    libxl_cdrom_insert(ctx, domid, &disk, NULL);
> > +    /* ATM the existence of the backing file is not checked for qdisk
> > +     * in libxl_cdrom_insert() because RAW is used for remote
> > +     * protocols as well as plain files.  This will ideally be changed
> > +     * for 4.4, but this work-around fixes the problem of "cd-insert"
> > +     * returning success for non-existent files. */
> > +    if (disk.format != LIBXL_DISK_FORMAT_EMPTY
> > +        && stat(disk.pdev_path, &b)) {
> > +        fprintf(stderr, "Cannot stat file: %s\n",
> > +                disk.pdev_path);
> You are leaking buf here, I know xl is just about to exit, but it might
> be best to to define a label below that contains:
Oops!  Sorry about that...

> > +        return 1;
> ERROR_INVAL
>
> > +    }
> > +
> > +    if (libxl_cdrom_insert(ctx, domid, &disk, NULL))
> > +        rc=1;
> You could use the return value of libxl_cdrom_insert instead of 1.
I sort of assumed that libxl_cdrom_insert() was a negative value, and 
that I wanted xl to return 1.
I'll send a respin w/ the leak fixed.

 -George

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