[libvirt] [PATCH v2] storage: Sanitize pool target paths
Cole Robinson
crobinso at redhat.com
Mon May 24 18:51:04 UTC 2010
On 05/21/2010 02:33 PM, Eric Blake wrote:
> On 05/21/2010 11:05 AM, Cole Robinson wrote:
>> Spurious / in a pool target path makes life difficult for apps using the
>> GetVolByPath, and doing other path based comparisons with pools. This
>> has caused a few issues for virt-manager users:
>>
>> https://bugzilla.redhat.com/show_bug.cgi?id=494005
>> https://bugzilla.redhat.com/show_bug.cgi?id=593565
>>
>> Add a new util API which removes spurious /, virFileSanitizePath. Sanitize
>> target paths when parsing pool XML, and for paths passed to GetVolByPath.
>>
>> v2: Leading // must be preserved, properly sanitize path=/, sanitize
>> away /./ -> /
>
> Nice - you caught one case that my review did not ("/" as the entire path).
>
>> +/* Remove spurious / characters from a path. The result must be freed */
>> +char *
>> +virFileSanitizePath(const char *path)
>> +{
>> + const char *cur = path;
>> + char *cleanpath;
>> + int idx = 0;
>> +
>> + cleanpath = strdup(path);
>> + if (!cleanpath) {
>> + virReportOOMError();
>> + return NULL;
>> + }
>> +
>> + /* Starting with // is valid posix, but ///foo == /foo */
>> + if (cur[0] == '/' && cur[1] == '/' && cur[2] != '/') {
>> + cleanpath[0] = '/';
>> + cleanpath[1] = '/';
>
> Delete these two lines; since cleanpath was created by strdup(), they
> are redundant assignments.
>
Will do
>> + idx = 2;
>> + cur += 2;
>> + }
>> +
>> + /* Sanitize path in place */
>> + while (*cur != '\0') {
>> + if (*cur != '/') {
>> + cleanpath[idx++] = *cur++;
>> + continue;
>> + }
>> +
>> + /* Skip all extra / */
>> + while (*cur == '/') {
>> + cur++;
>> +
>> + /* Resolve away /./ to just / */
>> + if (cur[0] == '.' && cur[1] == '/')
>> + cur++;
>> + }
>
> That doesn't simplify "./a" to "a", nor "b/." to "b"
>
Argh, good point.
>> +
>> + /* Don't add a trailing / unless path is only made of / */
>> + if (idx != 0 && *cur == '\0')
>> + break;
>
> This incorrectly collapses plain "//" to "/".
>
Actually we never entered the while() loop with a path of just //, so
this worked in practice.
>> +
>> + cleanpath[idx++] = '/';
>> + }
>
> Maybe a better approach is this pseudo-code:
>
> if (2 leading slashes) {
> advance 2
> if (end) return
> } else if (leading slash)
> advance 1
> do {
> advance past all slashes - they are redundant from previous round
> if (./ or .-end) advance 1 and continue
> copy all non-slashes
> copy one slash
> } while (!end)
> if (trailing slash)
> back up 1
>
I didn't end up going with this configuration, but the resulting code
isn't too bad, and seems to cover all the tests I could think up.
Updated patch sending shortly.
Thanks,
Cole
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