TOMOYO: Add description of lists and structures.

This patch adds some descriptions of lists and structures.
This patch contains no code changes.

Signed-off-by: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
Signed-off-by: James Morris <jmorris@namei.org>

1 files changed, 115 insertions, 6 deletions

diff --git a/security/tomoyo/file.c b/security/tomoyo/file.c
index ab0cd3538510..5ae3a571559f 100644
--- a/security/tomoyo/file.c
+++ b/security/tomoyo/file.c
@@ -14,21 +14,50 @@
 #include "realpath.h"
 #define ACC_MODE(x) ("\000\004\002\006"[(x)&O_ACCMODE])
 
-/* Structure for "allow_read" keyword. */
+/*
+ * tomoyo_globally_readable_file_entry is a structure which is used for holding
+ * "allow_read" entries.
+ * It has following fields.
+ *
+ *  (1) "list" which is linked to tomoyo_globally_readable_list .
+ *  (2) "filename" is a pathname which is allowed to open(O_RDONLY).
+ *  (3) "is_deleted" is a bool which is true if marked as deleted, false
+ *      otherwise.
+ */
 struct tomoyo_globally_readable_file_entry {
         struct list_head list;
         const struct tomoyo_path_info *filename;
         bool is_deleted;
 };
 
-/* Structure for "file_pattern" keyword. */
+/*
+ * tomoyo_pattern_entry is a structure which is used for holding
+ * "tomoyo_pattern_list" entries.
+ * It has following fields.
+ *
+ *  (1) "list" which is linked to tomoyo_pattern_list .
+ *  (2) "pattern" is a pathname pattern which is used for converting pathnames
+ *      to pathname patterns during learning mode.
+ *  (3) "is_deleted" is a bool which is true if marked as deleted, false
+ *      otherwise.
+ */
 struct tomoyo_pattern_entry {
         struct list_head list;
         const struct tomoyo_path_info *pattern;
         bool is_deleted;
 };
 
-/* Structure for "deny_rewrite" keyword. */
+/*
+ * tomoyo_no_rewrite_entry is a structure which is used for holding
+ * "deny_rewrite" entries.
+ * It has following fields.
+ *
+ *  (1) "list" which is linked to tomoyo_no_rewrite_list .
+ *  (2) "pattern" is a pathname which is by default not permitted to modify
+ *      already existing content.
+ *  (3) "is_deleted" is a bool which is true if marked as deleted, false
+ *      otherwise.
+ */
 struct tomoyo_no_rewrite_entry {
         struct list_head list;
         const struct tomoyo_path_info *pattern;
@@ -141,7 +170,31 @@ static int tomoyo_update_single_path_acl(const u8 type, const char *filename,
                                          struct tomoyo_domain_info *
                                          const domain, const bool is_delete);
 
-/* The list for "struct tomoyo_globally_readable_file_entry". */
+/*
+ * tomoyo_globally_readable_list is used for holding list of pathnames which
+ * are by default allowed to be open()ed for reading by any process.
+ *
+ * An entry is added by
+ *
+ * # echo 'allow_read /lib/libc-2.5.so' > \
+ *                               /sys/kernel/security/tomoyo/exception_policy
+ *
+ * and is deleted by
+ *
+ * # echo 'delete allow_read /lib/libc-2.5.so' > \
+ *                               /sys/kernel/security/tomoyo/exception_policy
+ *
+ * and all entries are retrieved by
+ *
+ * # grep ^allow_read /sys/kernel/security/tomoyo/exception_policy
+ *
+ * In the example above, any process is allowed to
+ * open("/lib/libc-2.5.so", O_RDONLY).
+ * One exception is, if the domain which current process belongs to is marked
+ * as "ignore_global_allow_read", current process can't do so unless explicitly
+ * given "allow_read /lib/libc-2.5.so" to the domain which current process
+ * belongs to.
+ */
 static LIST_HEAD(tomoyo_globally_readable_list);
 static DECLARE_RWSEM(tomoyo_globally_readable_list_lock);
 
@@ -256,7 +309,35 @@ bool tomoyo_read_globally_readable_policy(struct tomoyo_io_buffer *head)
         return done;
 }
 
-/* The list for "struct tomoyo_pattern_entry". */
+/* tomoyo_pattern_list is used for holding list of pathnames which are used for
+ * converting pathnames to pathname patterns during learning mode.
+ *
+ * An entry is added by
+ *
+ * # echo 'file_pattern /proc/\$/mounts' > \
+ *                             /sys/kernel/security/tomoyo/exception_policy
+ *
+ * and is deleted by
+ *
+ * # echo 'delete file_pattern /proc/\$/mounts' > \
+ *                             /sys/kernel/security/tomoyo/exception_policy
+ *
+ * and all entries are retrieved by
+ *
+ * # grep ^file_pattern /sys/kernel/security/tomoyo/exception_policy
+ *
+ * In the example above, if a process which belongs to a domain which is in
+ * learning mode requested open("/proc/1/mounts", O_RDONLY),
+ * "allow_read /proc/\$/mounts" is automatically added to the domain which that
+ * process belongs to.
+ *
+ * It is not a desirable behavior that we have to use /proc/\$/ instead of
+ * /proc/self/ when current process needs to access only current process's
+ * information. As of now, LSM version of TOMOYO is using __d_path() for
+ * calculating pathname. Non LSM version of TOMOYO is using its own function
+ * which pretends as if /proc/self/ is not a symlink; so that we can forbid
+ * current process from accessing other process's information.
+ */
 static LIST_HEAD(tomoyo_pattern_list);
 static DECLARE_RWSEM(tomoyo_pattern_list_lock);
 
@@ -377,7 +458,35 @@ bool tomoyo_read_file_pattern(struct tomoyo_io_buffer *head)
         return done;
 }
 
-/* The list for "struct tomoyo_no_rewrite_entry". */
+/*
+ * tomoyo_no_rewrite_list is used for holding list of pathnames which are by
+ * default forbidden to modify already written content of a file.
+ *
+ * An entry is added by
+ *
+ * # echo 'deny_rewrite /var/log/messages' > \
+ *                              /sys/kernel/security/tomoyo/exception_policy
+ *
+ * and is deleted by
+ *
+ * # echo 'delete deny_rewrite /var/log/messages' > \
+ *                              /sys/kernel/security/tomoyo/exception_policy
+ *
+ * and all entries are retrieved by
+ *
+ * # grep ^deny_rewrite /sys/kernel/security/tomoyo/exception_policy
+ *
+ * In the example above, if a process requested to rewrite /var/log/messages ,
+ * the process can't rewrite unless the domain which that process belongs to
+ * has "allow_rewrite /var/log/messages" entry.
+ *
+ * It is not a desirable behavior that we have to add "\040(deleted)" suffix
+ * when we want to allow rewriting already unlink()ed file. As of now,
+ * LSM version of TOMOYO is using __d_path() for calculating pathname.
+ * Non LSM version of TOMOYO is using its own function which doesn't append
+ * " (deleted)" suffix if the file is already unlink()ed; so that we don't
+ * need to worry whether the file is already unlink()ed or not.
+ */
 static LIST_HEAD(tomoyo_no_rewrite_list);
 static DECLARE_RWSEM(tomoyo_no_rewrite_list_lock);