[Libguestfs] [PATCH 1/2] daemon: run 'udevadm settle' with --exit-if-exists option
Pavel Butsykin
pbutsykin at virtuozzo.com
Thu Apr 13 08:55:50 UTC 2017
On 13.04.2017 00:11, Richard W.M. Jones wrote:
> On Wed, Apr 12, 2017 at 05:01:10PM +0300, Pavel Butsykin wrote:
>> Add udev_settle_file() to run 'udevadm settle' with --exit-if-exists option. It
>> will slightly reduce the waiting-time for pending events if we need to wait
>> for events related to a particular device/file.
>>
>> Signed-off-by: Pavel Butsykin <pbutsykin at virtuozzo.com>
>> ---
>> daemon/daemon.h | 2 ++
>> daemon/guestfsd.c | 20 ++++++++++++++++----
>> 2 files changed, 18 insertions(+), 4 deletions(-)
>>
>> diff --git a/daemon/daemon.h b/daemon/daemon.h
>> index 79a5288f6..90ebaafbe 100644
>> --- a/daemon/daemon.h
>> +++ b/daemon/daemon.h
>> @@ -141,6 +141,8 @@ extern int parse_btrfsvol (const char *desc, mountable_t *mountable);
>>
>> extern int prog_exists (const char *prog);
>>
>> +extern void udev_settle_file (const char *file);
>> +
>> extern void udev_settle (void);
>>
>> extern int random_name (char *template);
>> diff --git a/daemon/guestfsd.c b/daemon/guestfsd.c
>> index 85ce5d2ad..dccfa15bc 100644
>> --- a/daemon/guestfsd.c
>> +++ b/daemon/guestfsd.c
>> @@ -1213,13 +1213,18 @@ random_name (char *template)
>> * fussed if it fails.
>> */
>> void
>> -udev_settle (void)
>> +udev_settle_file (const char *file)
>> {
>> - char cmd[80];
>> + size_t cmd_size = strlen (str_udevadm) +
>> + sizeof (" settle") +
>> + sizeof (" --debug") +
>> + (file ? sizeof (" --exit-if-exists=") + strlen (file) : 0);
>> + char *cmd = malloc (cmd_size);
>> int r;
>>
>> - snprintf (cmd, sizeof cmd, "%s%s settle",
>> - str_udevadm, verbose ? " --debug" : "");
>> + snprintf(cmd, cmd_size, "%s%s settle%s%s",
>> + str_udevadm, verbose ? " --debug" : "",
>> + file ? " --exit-if-exists=" : "", file ? file : "");
>> if (verbose)
>> printf ("%s\n", cmd);
>> r = system (cmd);
>> @@ -1227,6 +1232,13 @@ udev_settle (void)
>> perror ("system");
>> else if (!WIFEXITED (r) || WEXITSTATUS (r) != 0)
>> fprintf (stderr, "warning: udevadm command failed\n");
>> + free (cmd);
>
> There are some ugly quoting (and hence, possibly, security) problems
> with this patch.
>
> It's more secure and also much simpler to call ADD_ARG + commandv
> here. For an example of how to use it, see:
>
> https://github.com/libguestfs/libguestfs/blob/master/daemon/mkfs.c#L41-L247
I agree, it would be better, thanks!
> Rich.
>
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