[PATCH][BZ #15763][BZ #14752] Restrict shm_open and shm_unlink to SHMDIR.

[OndÅej BÃlka <neleai at seznam dot cz>]

Hi, this patch adds validation restrict shm_open into a SHMDIR
directory.

A manpage says that it is only recomanded for portability, it is ok to
break nonportable apps? If not then close 15763.

As nobody bothered to test posix shmopen implementations I will not add
validation until its fixed.

OK to commit?


	[BZ #14752], [BZ #15763]
	* sysdeps/unix/sysv/linux/shm_open.c (shm_open, shm_unlink):
	Validate name.
	* rt/tst_shm.c: Add test for escaping directory.

diff --git a/rt/tst-shm.c b/rt/tst-shm.c
index f9d5ab0..cb4b1ee 100644
--- a/rt/tst-shm.c
+++ b/rt/tst-shm.c
@@ -134,6 +134,14 @@ do_test (void)
   int status2;
   struct stat64 st;
 
+  fd = shm_open ("/../escaped", O_RDWR | O_CREAT | O_TRUNC | O_EXCL, 0600);
+  if (fd != -1)
+    {
+      perror ("read file outside of SHMDIR directory");
+      return 1;
+    }
+
+
   /* Create the shared memory object.  */
   fd = shm_open ("/shm-test", O_RDWR | O_CREAT | O_TRUNC | O_EXCL, 0600);
   if (fd == -1)
diff --git a/sysdeps/unix/sysv/linux/shm_open.c b/sysdeps/unix/sysv/linux/shm_open.c
index 41d9315..1e11392 100644
--- a/sysdeps/unix/sysv/linux/shm_open.c
+++ b/sysdeps/unix/sysv/linux/shm_open.c
@@ -148,14 +148,15 @@ shm_open (const char *name, int oflag, mode_t mode)
   while (name[0] == '/')
     ++name;
 
-  if (name[0] == '\0')
+  namelen = strlen (name);
+
+  /* Validate the filename.  */
+  if (name[0] == '\0' || namelen > NAME_MAX || strchr (name, '/'))
     {
-      /* The name "/" is not supported.  */
       __set_errno (EINVAL);
       return -1;
     }
 
-  namelen = strlen (name);
   fname = (char *) alloca (mountpoint.dirlen + namelen + 1);
   __mempcpy (__mempcpy (fname, mountpoint.dir, mountpoint.dirlen),
 	     name, namelen + 1);
@@ -237,14 +238,15 @@ shm_unlink (const char *name)
   while (name[0] == '/')
     ++name;
 
-  if (name[0] == '\0')
+  namelen = strlen (name);
+
+  /* Validate the filename.  */
+  if (name[0] == '\0' || namelen > NAME_MAX || strchr (name, '/'))
     {
-      /* The name "/" is not supported.  */
       __set_errno (ENOENT);
       return -1;
     }
 
-  namelen = strlen (name);
   fname = (char *) alloca (mountpoint.dirlen + namelen + 1);
   __mempcpy (__mempcpy (fname, mountpoint.dir, mountpoint.dirlen),
 	     name, namelen + 1);