Refactor shm_{open,unlink} code to separate Linux-specific directory choice from POSIX-generic code.

5 files changed, 132 insertions, 55 deletions

diff --git a/sysdeps/posix/Makefile b/sysdeps/posix/Makefile
index b58aa6aadb..8e5f7c3bba 100644
--- a/sysdeps/posix/Makefile
+++ b/sysdeps/posix/Makefile
@@ -3,3 +3,7 @@ L_tmpnam  = 20
 TMP_MAX   = 238328
 L_ctermid = 9
 L_cuserid = 9
+
+ifeq ($(subdir),rt)
+librt-routines += shm-directory
+endif
diff --git a/sysdeps/posix/shm-directory.c b/sysdeps/posix/shm-directory.c
new file mode 100644
index 0000000000..aea5f963b0
--- /dev/null
+++ b/sysdeps/posix/shm-directory.c
@@ -0,0 +1,35 @@
+/* Determine directory for shm/sem files.  Generic POSIX version.
+   Copyright (C) 2014 Free Software Foundation, Inc.
+   This file is part of the GNU C Library.
+
+   The GNU C Library is free software; you can redistribute it and/or
+   modify it under the terms of the GNU Lesser General Public
+   License as published by the Free Software Foundation; either
+   version 2.1 of the License, or (at your option) any later version.
+
+   The GNU C Library is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+   Lesser General Public License for more details.
+
+   You should have received a copy of the GNU Lesser General Public
+   License along with the GNU C Library; if not, see
+   <http://www.gnu.org/licenses/>.  */
+
+#include "shm-directory.h"
+#include <unistd.h>
+
+#if _POSIX_MAPPED_FILES
+
+# include <paths.h>
+
+# define SHMDIR (_PATH_DEV "shm/")
+
+const char *
+__shm_directory (size_t *len)
+{
+  *len = sizeof SHMDIR - 1;
+  return SHMDIR;
+}
+
+#endif
diff --git a/sysdeps/posix/shm-directory.h b/sysdeps/posix/shm-directory.h
new file mode 100644
index 0000000000..1c4d965b28
--- /dev/null
+++ b/sysdeps/posix/shm-directory.h
@@ -0,0 +1,63 @@
+/* Header for directory for shm/sem files.
+   Copyright (C) 2014 Free Software Foundation, Inc.
+   This file is part of the GNU C Library.
+
+   The GNU C Library is free software; you can redistribute it and/or
+   modify it under the terms of the GNU Lesser General Public
+   License as published by the Free Software Foundation; either
+   version 2.1 of the License, or (at your option) any later version.
+
+   The GNU C Library is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+   Lesser General Public License for more details.
+
+   You should have received a copy of the GNU Lesser General Public
+   License along with the GNU C Library; if not, see
+   <http://www.gnu.org/licenses/>.  */
+
+#ifndef _SHM_DIRECTORY_H
+
+#include <errno.h>
+#include <limits.h>
+#include <stdbool.h>
+#include <stdlib.h>
+#include <string.h>
+
+extern const char *__shm_directory (size_t *len);
+
+/* This defines local variables SHM_DIR and SHM_DIRLEN, giving the
+   directory prefix (with trailing slash) and length (not including '\0'
+   terminator) of the directory used for shm files.  If that cannot be
+   determined, it sets errno to ENOSYS and returns RETVAL_FOR_INVALID.
+
+   This uses the local variable NAME as an lvalue, and increments it past
+   any leading slashes.  It then defines the local variable NAMELEN, giving
+   strlen (NAME) + 1.  If NAME is invalid, it sets errno to
+   ERRNO_FOR_INVALID and returns RETVAL_FOR_INVALID.  Finally, it defines
+   the local variable SHM_NAME, giving the absolute file name of the shm
+   file corresponding to NAME.  */
+
+#define SHM_GET_NAME(errno_for_invalid, retval_for_invalid)		      \
+  size_t shm_dirlen;							      \
+  const char *shm_dir = __shm_directory (&shm_dirlen);			      \
+  /* If we don't know what directory to use, there is nothing we can do.  */  \
+  if (__glibc_unlikely (shm_dir == NULL))				      \
+    {									      \
+      __set_errno (ENOSYS);						      \
+      return retval_for_invalid;					      \
+    }									      \
+  /* Construct the filename.  */					      \
+  while (name[0] == '/')						      \
+    ++name;								      \
+  size_t namelen = strlen (name) + 1;					      \
+  /* Validate the filename.  */						      \
+  if (namelen == 1 || namelen >= NAME_MAX || strchr (name, '/') != NULL)      \
+    {									      \
+      __set_errno (errno_for_invalid);					      \
+      return retval_for_invalid;					      \
+    }									      \
+  char *shm_name = __alloca (shm_dirlen + namelen);			      \
+  __mempcpy (__mempcpy (shm_name, shm_dir, shm_dirlen), name, namelen)
+
+#endif	/* shm-directory.h */
diff --git a/sysdeps/posix/shm_open.c b/sysdeps/posix/shm_open.c
index 456b3d8b8f..064fecf3f2 100644
--- a/sysdeps/posix/shm_open.c
+++ b/sysdeps/posix/shm_open.c
@@ -19,50 +19,41 @@
 #include <unistd.h>
 
 #if ! _POSIX_MAPPED_FILES
-#include <rt/shm_open.c>
+
+# include <rt/shm_open.c>
 
 #else
 
-#include <errno.h>
-#include <sys/mman.h>
-#include <fcntl.h>
-#include <string.h>
-#include <stdlib.h>
-#include <paths.h>
+# include <fcntl.h>
+# include <shm-directory.h>
 
-#define SHMDIR	(_PATH_DEV "shm/")
 
 /* Open shared memory object.  */
 int
 shm_open (const char *name, int oflag, mode_t mode)
 {
-  size_t namelen;
-  char *fname;
-  int fd;
-
-  /* Construct the filename.  */
-  while (name[0] == '/')
-    ++name;
-
-  if (name[0] == '\0')
-    {
-      /* The name "/" is not supported.  */
-      __set_errno (EINVAL);
-      return -1;
-    }
-
-  namelen = strlen (name);
-  fname = (char *) __alloca (sizeof SHMDIR - 1 + namelen + 1);
-  __mempcpy (__mempcpy (fname, SHMDIR, sizeof SHMDIR - 1),
-	     name, namelen + 1);
-
-  fd = open (name, oflag, mode);
+  SHM_GET_NAME (EINVAL, -1);
+
+# ifdef O_NOFOLLOW
+  oflag |= O_NOFOLLOW;
+# endif
+# ifdef O_CLOEXEC
+  oflag |= O_CLOEXEC;
+# endif
+  int fd = open (shm_name, oflag, mode);
+  if (fd == -1 && __glibc_unlikely (errno == EISDIR))
+    /* It might be better to fold this error with EINVAL since
+       directory names are just another example for unsuitable shared
+       object names and the standard does not mention EISDIR.  */
+    __set_errno (EINVAL);
+
+# ifndef O_CLOEXEC
   if (fd != -1)
     {
       /* We got a descriptor.  Now set the FD_CLOEXEC bit.  */
       int flags = fcntl (fd, F_GETFD, 0);
 
-      if (__builtin_expect (flags, 0) != -1)
+      if (__glibc_likely (flags != -1))
 	{
 	  flags |= FD_CLOEXEC;
 	  flags = fcntl (fd, F_SETFD, flags);
@@ -77,8 +68,9 @@ shm_open (const char *name, int oflag, mode_t mode)
 	  __set_errno (save_errno);
 	}
     }
+# endif
 
   return fd;
 }
 
-#endif
+#endif  /* _POSIX_MAPPED_FILES */
diff --git a/sysdeps/posix/shm_unlink.c b/sysdeps/posix/shm_unlink.c
index dc94e1692b..81c3a02642 100644
--- a/sysdeps/posix/shm_unlink.c
+++ b/sysdeps/posix/shm_unlink.c
@@ -24,37 +24,20 @@
 #else
 
 #include <errno.h>
-#include <sys/mman.h>
 #include <string.h>
-#include <stdlib.h>
-#include <paths.h>
+#include "shm-directory.h"
 
-#define SHMDIR	(_PATH_DEV "shm/")
 
 /* Remove shared memory object.  */
 int
 shm_unlink (const char *name)
 {
-  size_t namelen;
-  char *fname;
-
-  /* Construct the filename.  */
-  while (name[0] == '/')
-    ++name;
-
-  if (name[0] == '\0')
-    {
-      /* The name "/" is not supported.  */
-      __set_errno (EINVAL);
-      return -1;
-    }
-
-  namelen = strlen (name);
-  fname = (char *) __alloca (sizeof SHMDIR - 1 + namelen + 1);
-  __mempcpy (__mempcpy (fname, SHMDIR, sizeof SHMDIR - 1),
-	     name, namelen + 1);
-
-  return unlink (name);
+  SHM_GET_NAME (ENOENT, -1);
+
+  int result = unlink (shm_name);
+  if (result < 0 && errno == EPERM)
+    __set_errno (EACCES);
+  return result;
 }
 
 #endif