[pacman-dev] [PATCH] Allow querying directory ownership
Menachem Moystoviz
moystovi at g.jct.ac.il
Fri Sep 7 07:06:25 EDT 2012
I'm not a dev, nor the original author of the patch, but...
On Fri, Sep 7, 2012 at 10:29 AM, Allan McRae <allan at archlinux.org> wrote:
> On 06/09/12 13:34, Andrew Gregory wrote:
>> The restriction of not checking the ownership of a directory is
>> unnecessary given that all the package filelists contain this
>> information. Remove this restriction, with the expectation that you
>> might get multiple packages returned for a given directory.
>> Additionally attempt to minimise the number of files getting through
>> to the slow realpath call.
>>
>> Original-work-by: Dan McGee <dan at archlinux.org>
>> Original-work-by: Allan McRae <allan at archlinux.org>
>> Signed-off-by: Andrew Gregory <andrew.gregory.8 at gmail.com>
>> ---
>>
>> Applies on top of my other -Qo patches queued in Allan's
>> working-split/query-owner branch.
>>
>> src/pacman/query.c | 61 +++++++++++++++++++++++++++++++++++++++++-------------
>> 1 file changed, 47 insertions(+), 14 deletions(-)
>>
>> diff --git a/src/pacman/query.c b/src/pacman/query.c
>> index 92219e8..06505eb 100644
>> --- a/src/pacman/query.c
>> +++ b/src/pacman/query.c
>> @@ -97,6 +97,7 @@ static int query_fileowner(alpm_list_t *targets)
>> size_t rootlen;
>> alpm_list_t *t;
>> alpm_db_t *db_local;
>> + alpm_list_t *packages;
>>
>> /* This code is here for safety only */
>> if(targets == NULL) {
>> @@ -129,13 +130,14 @@ static int query_fileowner(alpm_list_t *targets)
>> }
>>
>> db_local = alpm_get_localdb(config->handle);
>> + packages = alpm_db_get_pkgcache(db_local);
>>
>> for(t = targets; t; t = alpm_list_next(t)) {
>> char *filename = NULL, *dname = NULL, *rpath = NULL;
>> const char *bname;
>> struct stat buf;
>> alpm_list_t *i;
>> - size_t len;
>> + size_t len, is_dir, bname_len, pbname_len;
>> int found = 0;
>>
>> if((filename = strdup(t->data)) == NULL) {
>> @@ -163,15 +165,20 @@ static int query_fileowner(alpm_list_t *targets)
>> }
>> }
>>
>> - if(S_ISDIR(buf.st_mode)) {
>> - pm_printf(ALPM_LOG_ERROR,
>> - _("cannot determine ownership of directory '%s'\n"), filename);
>> - goto targcleanup;
>> + if((is_dir = S_ISDIR(buf.st_mode))) {
>> + /* the entire filename is safe to resolve if we know it points to a dir,
>> + * and it's necessary in case it ends in . or .. */
>> + dname = realpath(filename, NULL);
>> + bname = mbasename(dname);
>> + rpath = mdirname(dname);
>> + } else {
>> + bname = mbasename(filename);
>> + dname = mdirname(filename);
>> + rpath = realpath(dname, NULL);
>> }
>>
>> - bname = mbasename(filename);
>> - dname = mdirname(filename);
>> - rpath = realpath(dname, NULL);
>> + bname_len = strlen(bname);
>> + pbname_len = bname_len + (is_dir ? 1 : 0);
>>
>> if(!dname || !rpath) {
>> pm_printf(ALPM_LOG_ERROR, _("cannot determine real path for '%s': %s\n"),
>> @@ -179,7 +186,7 @@ static int query_fileowner(alpm_list_t *targets)
>> goto targcleanup;
>> }
>>
>> - for(i = alpm_db_get_pkgcache(db_local); i && !found; i = alpm_list_next(i)) {
>> + for(i = packages; i && (!found || is_dir); i = alpm_list_next(i)) {
>> alpm_pkg_t *info = i->data;
>> alpm_filelist_t *filelist = alpm_pkg_get_files(info);
>> size_t j;
>> @@ -188,22 +195,48 @@ static int query_fileowner(alpm_list_t *targets)
>> const alpm_file_t *file = filelist->files + j;
>> char *ppath, *pdname;
>> const char *pkgfile = file->name;
>> + size_t pkgfile_len = strlen(pkgfile);
>> +
>> + /* make sure pkgfile and target are of the same type */
>> + if(!is_dir != !(pkgfile[pkgfile_len - 1] == '/')) {
>
> !!! - literally.... How about:
>
> if (is_dir && (pkgfile[pkgfile_len - 1] != '/'))
This isn't the same check - Andrew's check verifies that is_dir XOR
(pkgfile's last character is not '/' (i.e. pkgfile names a file
path)),
is true, while your test is for AND. This way of defining XOR is quite
confusing, though - isn't there a clearer way? (i.e. macros, inline
functions?)
>
>> + continue;
>> + }
>> +
>> + /* make sure pkgfile is long enough */
>> + if(pkgfile_len < pbname_len) {
>> + continue;
>> + }
>
> If I understand this correctly, we are comparing the length of the final
> component of the passed in parameter to the entire filename length from
> the package. I think that it would be quite uncommon to hit the
> continue here, so that can be removed.
>
I think you mean to say that we replace this if(){continue;} with
if(!){...} wrapping the rest of the loop?
That would make sense if this branch is costly.
>>
>> - /* avoid the costly realpath usage if the basenames don't match */
>> - if(strcmp(mbasename(pkgfile), bname) != 0) {
>> + /* make sure pbname_len takes us to the start of a path component */
>> + if(pbname_len != pkgfile_len && pkgfile[pkgfile_len - pbname_len - 1] != '/') {
>
> With the above removal:
> if (pbname_len > pkgfile_len)
>
>> + continue;
>> + }
>> +
>> + /* compare basename with bname */
>> + if(strncmp(pkgfile + pkgfile_len - pbname_len, bname, bname_len) != 0) {
>
> Why an strncmp here? strcmp will do the same comparison...
>
In order to make sure that we don't run into buffer overflow issues -
http://stackoverflow.com/questions/448563/am-i-correct-that-strcmp-is-equivalent-and-safe-for-literals
>> continue;
>> }
>>
>> /* concatenate our file and the root path */
>> - if(rootlen + 1 + strlen(pkgfile) > PATH_MAX) {
>> + if(rootlen + 1 + pkgfile_len > PATH_MAX) {
>> path[rootlen] = '\0'; /* reset path for error message */
>> pm_printf(ALPM_LOG_ERROR, _("path too long: %s%s\n"), path, pkgfile);
>> continue;
>> }
>> strcpy(path + rootlen, pkgfile);
>>
>> - pdname = mdirname(path);
>> - ppath = realpath(pdname, NULL);
>> + /* check that the file exists on disk and is the correct type */
>> + if(lstat(path, &buf) == -1 || !is_dir != !S_ISDIR(buf.st_mode)) {
>
> !!! again. How about:
>
> if(is_dir && lstat(path, &buf) == 0 && !S_ISDIR(buf.st_mode))
>
> which is what I think is being tested here.
Again, your fix doesn't match the original test - Andrew's test
verifies that the file either doesn't exist
or that (the file is a directory) XOR is_dir is true.
>
> But I wonder if we really need this... I believe this is to avoid
> "strange" results when people replace directories in a package with
> symlinks to directories in another package. The more I think about
> this, the more I want to just remove our special case handling of this
> in general. A directory in a package and a symlink on the filesystem
> should just be a conflict. So unless I am missing another reason for
> this, get rid of it.
>
No comment, as I do not know the codebase well enough to respond.
>> + continue;
>> + }
>> +
>> + if(is_dir) {
>> + pdname = realpath(path, NULL);
>> + ppath = mdirname(pdname);
>> + } else {
>> + pdname = mdirname(path);
>> + ppath = realpath(pdname, NULL);
>> + }
>> free(pdname);
>
> Umm... why calculate pdname just to free it immediately?
Since we need to use it to calculate ppath?
>
>> if(!ppath) {
>>
>
>
Overall, I can't really judge the quality of Andrew's patch, but I definitely
do not agree with the comments given by Allan.
HTH in my own way,
Gesh
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