From c0ab6e56dcb7ca9903d460247cb464e769ae6e77 Mon Sep 17 00:00:00 2001 From: Casey Schaufler Date: Fri, 11 Oct 2013 18:06:39 -0700 Subject: Smack: Implement lock security mode Linux file locking does not follow the same rules as other mechanisms. Even though it is a write operation a process can set a read lock on files which it has open only for read access. Two programs with read access to a file can use read locks to communicate. This is not acceptable in a Mandatory Access Control environment. Smack treats setting a read lock as the write operation that it is. Unfortunately, many programs assume that setting a read lock is a read operation. These programs are unhappy in the Smack environment. This patch introduces a new access mode (lock) to address this problem. A process with lock access to a file can set a read lock. A process with write access to a file can set a read lock or a write lock. This prevents a situation where processes are granted write access just so they can set read locks. Targeted for git://git.gitorious.org/smack-next/kernel.git Signed-off-by: Casey Schaufler --- security/smack/smack_access.c | 10 ++++++++++ 1 file changed, 10 insertions(+) (limited to 'security/smack/smack_access.c') diff --git a/security/smack/smack_access.c b/security/smack/smack_access.c index b3b59b1e93d6..14293cd9b1e5 100644 --- a/security/smack/smack_access.c +++ b/security/smack/smack_access.c @@ -84,6 +84,8 @@ int log_policy = SMACK_AUDIT_DENIED; * * Do the object check first because that is more * likely to differ. + * + * Allowing write access implies allowing locking. */ int smk_access_entry(char *subject_label, char *object_label, struct list_head *rule_list) @@ -99,6 +101,11 @@ int smk_access_entry(char *subject_label, char *object_label, } } + /* + * MAY_WRITE implies MAY_LOCK. + */ + if ((may & MAY_WRITE) == MAY_WRITE) + may |= MAY_LOCK; return may; } @@ -245,6 +252,7 @@ out_audit: static inline void smack_str_from_perm(char *string, int access) { int i = 0; + if (access & MAY_READ) string[i++] = 'r'; if (access & MAY_WRITE) @@ -255,6 +263,8 @@ static inline void smack_str_from_perm(char *string, int access) string[i++] = 'a'; if (access & MAY_TRANSMUTE) string[i++] = 't'; + if (access & MAY_LOCK) + string[i++] = 'l'; string[i] = '\0'; } /** -- cgit v1.2.3