[pacman-dev] [PATCH] Fix segfault during install when a package update adds a new file to 'backup'

[Andrew Gregory]

On 04/01/16 at 10:52am, Will Miles wrote:
> When a new package release adds a new entry to the backup list, no hash exists
> for that file in the previously installed package version.  Fix two places
> where that nonexistent hash may be dereferenced.
> 
> Signed-off-by: Will Miles <wmiles at sgl.com>
> ---
>  lib/libalpm/add.c      | 2 +-
>  lib/libalpm/be_local.c | 4 +++-
>  2 files changed, 4 insertions(+), 2 deletions(-)
> 
> diff --git a/lib/libalpm/add.c b/lib/libalpm/add.c
> index f5c9a95..ff0b81d 100644
> --- a/lib/libalpm/add.c
> +++ b/lib/libalpm/add.c
> @@ -341,7 +341,7 @@ static int extract_single_file(alpm_handle_t *handle, struct archive *archive,
>  		_alpm_log(handle, ALPM_LOG_DEBUG, "checking hashes for %s\n", origfile);
>  		_alpm_log(handle, ALPM_LOG_DEBUG, "current:  %s\n", hash_local);
>  		_alpm_log(handle, ALPM_LOG_DEBUG, "new:      %s\n", hash_pkg);
> -		_alpm_log(handle, ALPM_LOG_DEBUG, "original: %s\n", hash_orig);
> +		_alpm_log(handle, ALPM_LOG_DEBUG, "original: %s\n", (hash_orig ? hash_orig : "NULL") );

All of these hashed can potentially be NULL if we encounter an error
when reading the file.  This check should be applied to all of them.

>  		if(hash_local && hash_pkg && strcmp(hash_local, hash_pkg) == 0) {
>  			/* local and new files are the same, updating anyway to get
> diff --git a/lib/libalpm/be_local.c b/lib/libalpm/be_local.c
> index f817822..5e39199 100644
> --- a/lib/libalpm/be_local.c
> +++ b/lib/libalpm/be_local.c
> @@ -1037,7 +1037,9 @@ int _alpm_local_db_write(alpm_db_t *db, alpm_pkg_t *info, alpm_dbinfrq_t inforeq
>  			fputs("%BACKUP%\n", fp);
>  			for(lp = info->backup; lp; lp = lp->next) {
>  				const alpm_backup_t *backup = lp->data;
> -				fprintf(fp, "%s\t%s\n", backup->name, backup->hash);
> +				if (backup->hash) {
> +					fprintf(fp, "%s\t%s\n", backup->name, backup->hash);
> +				}

We should still add these entries to the database even if we don't
have hashes for them.  Just skip printing the hash itself (or replace
it with an empty string) if it's NULL.

>  			}
>  			fputc('\n', fp);
>  		}
> -- 
> 2.6.3