tomoyo: reduce mmap_sem hold for mm->exe_file
The mm->exe_file is currently serialized with mmap_sem (shared) in order
to both safely (1) read the file and (2) compute the realpath by calling
tomoyo_realpath_from_path, making it an absolute overkill. Good users
will, on the other hand, make use of the more standard get_mm_exe_file(),
requiring only holding the mmap_sem to read the value, and relying on
reference
[akpm@linux-foundation.org: coding-style fixes]
Signed-off-by: Davidlohr Bueso <dbueso@suse.de>
Acked-by: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
Cc: James Morris <jmorris@namei.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/security/tomoyo/util.c b/security/tomoyo/util.c
index 2952ba5..b974a69 100644
--- a/security/tomoyo/util.c
+++ b/security/tomoyo/util.c
@@ -948,15 +948,18 @@
*/
const char *tomoyo_get_exe(void)
{
+ struct file *exe_file;
+ const char *cp;
struct mm_struct *mm = current->mm;
- const char *cp = NULL;
if (!mm)
return NULL;
- down_read(&mm->mmap_sem);
- if (mm->exe_file)
- cp = tomoyo_realpath_from_path(&mm->exe_file->f_path);
- up_read(&mm->mmap_sem);
+ exe_file = get_mm_exe_file(mm);
+ if (!exe_file)
+ return NULL;
+
+ cp = tomoyo_realpath_from_path(&exe_file->f_path);
+ fput(exe_file);
return cp;
}