[apparmor] [PATCH] parser: Restore --skip-bad-cache behavior when cache dir DNE

[Tyler Hicks]

When the cache directory does not exist, but --write-cache and
--skip-bad-cache are specified, the cache directory and the features
file should be created but writes to the cache directory should not
happen. This patch restores that behavior.

The errno values libapparmor's aa_policy_cache_new() uses to indicate
when the cache directory does not exist and when an existing, invalid
cache already exists needed to be separated out. They were both ENOENT
but now the latter situation uses EEXIST.

libapparmor also needed to be updated to not print an error message to
the syslog from aa_policy_cache_new() when the max_caches parameter is
0, indicating that a new cache should not be created, and the cache
directory does not exist. This is an error situation but a debug message
is more appropriate.

Signed-off-by: Tyler Hicks <tyhicks at canonical.com>
---

This patch is intended to be applied as a fixup patch at the end of the greater
patch series.

The approach taken is to modify the parser to recall into libapparmor, under
certain conditions, to continue supporting the parser's --skip-bad-cache and
--write-cache behavior when the cache directory does not exist.

 libraries/libapparmor/src/policy_cache.c |  6 ++++--
 parser/parser_main.c                     | 19 ++++++++++++++++++-
 2 files changed, 22 insertions(+), 3 deletions(-)

diff --git a/libraries/libapparmor/src/policy_cache.c b/libraries/libapparmor/src/policy_cache.c
index f685f0a..72c0176 100644
--- a/libraries/libapparmor/src/policy_cache.c
+++ b/libraries/libapparmor/src/policy_cache.c
@@ -78,7 +78,7 @@ static int init_cache_features(aa_policy_cache *policy_cache,
 	} else if (!aa_features_is_equal(policy_cache->features,
 					 kernel_features)) {
 		if (!create) {
-			errno = ENOENT;
+			errno = EEXIST;
 			return -1;
 		}
 
@@ -166,8 +166,10 @@ open:
 			if (mkdirat(dirfd, path, 0700) == 0)
 				goto open;
 			PERROR("Can't create cache directory '%s': %m\n", path);
-		} else {
+		} else if (create) {
 			PERROR("Can't update cache directory '%s': %m\n", path);
+		} else {
+			PDEBUG("Cache directory '%s' does not exist\n", path);
 		}
 
 		save = errno;
diff --git a/parser/parser_main.c b/parser/parser_main.c
index f274d00..3bb115d 100644
--- a/parser/parser_main.c
+++ b/parser/parser_main.c
@@ -918,13 +918,30 @@ int main(int argc, char *argv[])
 		if (create_cache_dir)
 			pwarn(_("The --create-cache-dir option is deprecated. Please use --write-cache.\n"));
 
+retry:
 		retval = aa_policy_cache_new(&policy_cache, features,
 					     AT_FDCWD, cacheloc, max_caches);
 		if (retval) {
-			if (errno != ENOENT) {
+			if (errno != ENOENT && errno != EEXIST) {
 				PERROR(_("Failed setting up policy cache (%s): %s\n"),
 				       cacheloc, strerror(errno));
 				return 1;
+			} else if (errno == ENOENT && max_caches == 0 &&
+				   write_cache && !cond_clear_cache) {
+				/**
+				 * --write-cache and --skip-bad-cache are
+				 * present and errno is ENOENT, meaning that
+				 * the cache dir does not exist. Legacy
+				 * behavior is to create the cache dir in this
+				 * situation so retry with a non-zero
+				 * max_caches. 2.9 went ahead and wrote to the
+				 * newly created cache dir. It has been decided,
+				 * as of r2927, that 2.10 will not write to the
+				 * new cache dir.
+				 */
+				write_cache = 0;
+				max_caches = 1;
+				goto retry;
 			}
 
 			if (show_cache) {
-- 
2.1.4