[pacman-dev] [PATCH 5/8] extract_single_file: consolidate symlink cases

[Allan McRae]

On 27/04/13 10:00, Andrew Gregory wrote:
> Signed-off-by: Andrew Gregory <andrew.gregory.8 at gmail.com>
> ---
>  lib/libalpm/add.c | 33 ++++++++-------------------------
>  1 file changed, 8 insertions(+), 25 deletions(-)
> 
> diff --git a/lib/libalpm/add.c b/lib/libalpm/add.c
> index 1d9db60..0b8aedf 100644
> --- a/lib/libalpm/add.c
> +++ b/lib/libalpm/add.c
> @@ -204,19 +204,17 @@ static int extract_single_file(alpm_handle_t *handle, struct archive *archive,
>  	 *  D            |   10  |  11 |  12
>  	 *
>  	 *  1,2,3- extract, no magic necessary. lstat (_alpm_lstat) will fail here.
> -	 *  4,5,6,7,8- conflict checks should have caught this. either overwrite
> +	 *  4,5,6,7,8,9- conflict checks should have caught this. either overwrite
>  	 *      or backup the file.
> -	 *  9- follow the symlink, hopefully it is a directory, check it.
> -	 *  10- file replacing directory- don't allow it.
> -	 *  11- don't extract symlink- a dir exists here. we don't want links to
> -	 *      links, etc.
> +	 *  10,11- file replacing directory- don't allow it.
>  	 *  12- skip extraction, dir already exists.
>  	 */
>  
> -	/* do both a lstat and a stat, so we can see what symlinks point to */
>  	struct stat lsbuf, sbuf;
> -	if(_alpm_lstat(filename, &lsbuf) != 0 || stat(filename, &sbuf) != 0) {
> -		/* cases 1,2,3: couldn't stat an existing file, skip all backup checks */
> +	if(stat(filename, &sbuf) != 0 || _alpm_lstat(filename, &lsbuf) != 0) {
> +		/* cases 1,2,3: file doesn't exist or is a broken symlink,
> +		 * skip all backup checks */
> +		/* TODO: should we really treat broken symlinks as if they don't exist? */

NO!  We definitely should not...

In fact, I'd like to see this patch result in this:

	 * (F=file, N=node, S=symlink, D=dir)
	 *               | F/N/S |   D
	 *  non-existent |   1   |   2
	 *  F/N/S        |   3   |   4
	 *  D            |   5   |   6

because now there is no difference between a file and a symlink.  Which
probably means getting rid of the lstat call (although I did not look at
the code to confirm...)

>  	} else {
>  		if(S_ISDIR(lsbuf.st_mode)) {
>  			if(S_ISDIR(entrymode)) {
> @@ -243,23 +241,8 @@ static int extract_single_file(alpm_handle_t *handle, struct archive *archive,
>  				archive_read_data_skip(archive);
>  				return 1;
>  			}
> -		} else if(S_ISLNK(lsbuf.st_mode) && S_ISDIR(entrymode)) {
> -			/* case 9: existing symlink, dir in package */
> -			if(S_ISDIR(sbuf.st_mode)) {
> -				/* the symlink on FS is to a directory, so we'll use it */
> -				_alpm_log(handle, ALPM_LOG_DEBUG, "extract: skipping symlink overwrite of %s\n",
> -						filename);
> -				archive_read_data_skip(archive);
> -				return 0;
> -			} else {
> -				/* this is BAD. symlink was not to a directory */
> -				_alpm_log(handle, ALPM_LOG_ERROR, _("extract: symlink %s does not point to dir\n"),
> -						filename);
> -				archive_read_data_skip(archive);
> -				return 1;
> -			}
> -		} else if(S_ISREG(lsbuf.st_mode) && S_ISDIR(entrymode)) {
> -			/* case 6: trying to overwrite file with dir */
> +		} else if(!S_ISDIR(lsbuf.st_mode) && S_ISDIR(entrymode)) {
> +			/* case 6,9: trying to overwrite file with dir */
>  			_alpm_log(handle, ALPM_LOG_DEBUG, "extract: overwriting file with dir %s\n",
>  					filename);
>  		} else if(S_ISREG(entrymode)) {
>