@@ -20,7 +20,10 @@ Deprecated and removed features, and other changes affecting compatibility:
Changes to build and runtime requirements:
- [Add changes to build and runtime requirements here]
+* On Linux, the shm_open, sem_open, and related functions now expect the
+ file shared memory file system to be mounted at /dev/shm. These functions
+ no longer search among the system's mount points for a suitable
+ replacement if /dev/shm is not available.
Security related changes:
@@ -132,8 +132,6 @@ libpthread-routines := pt-attr pt-attr-destroy pt-attr-getdetachstate \
sem-post sem-timedwait sem-trywait sem_unlink \
sem-wait sem-waitfast \
\
- shm-directory \
- \
cancellation \
cthreads-compat \
herrno \
@@ -168,7 +168,6 @@ libpthread {
GLIBC_PRIVATE {
__pthread_initialize_minimal;
- __shm_directory;
__pthread_threads;
__cthread_detach;
similarity index 56%
rename from sysdeps/nptl/shm-directory.h
rename to include/shm-directory.h
@@ -1,4 +1,4 @@
-/* Header for directory for shm/sem files. NPTL version.
+/* Header for directory for shm/sem files.
Copyright (C) 2014-2021 Free Software Foundation, Inc.
This file is part of the GNU C Library.
@@ -18,14 +18,24 @@
#ifndef _SHM_DIRECTORY_H
-#include <sysdeps/posix/shm-directory.h>
-
-/* For NPTL the __shm_directory function lives in libpthread.
- We don't want PLT calls from there. But it's also used from
- librt, so it cannot just be declared hidden. */
-
-#if IS_IN (libpthread)
-hidden_proto (__shm_directory)
-#endif
+#include <limits.h>
+#include <paths.h>
+#include <stdbool.h>
+
+/* The directory that contains shared POSIX objects. */
+#define SHMDIR _PATH_DEV "shm/"
+
+struct shmdir_name
+{
+ /* The combined prefix/name. The sizeof includes the terminating
+ NUL byte. 4 bytes are needed for the optional "sem." prefix. */
+ char name[sizeof (SHMDIR) + 4 + NAME_MAX];
+};
+
+/* Sets RESULT->name to the constructed name and returns 0 on success,
+ or -1 on failure. Includes the "sem." prefix in the name if
+ SEM_PREFIX is true. */
+int __shm_get_name (struct shmdir_name *result, const char *name,
+ bool sem_prefix);
#endif /* shm-directory.h */
@@ -137,7 +137,6 @@ libpthread-routines = nptl-init nptlfreeres vars events version pt-interp \
pthread_once \
old_pthread_atfork \
pthread_getcpuclockid \
- shm-directory \
sem_init sem_destroy \
sem_open sem_close sem_unlink \
sem_getvalue \
@@ -303,7 +303,6 @@ libpthread {
__pthread_unwind; __pthread_get_minstack;
__pthread_barrier_init; __pthread_barrier_wait;
__futex_abstimed_wait64; __futex_abstimed_wait_cancelable64;
- __shm_directory;
__libpthread_freeres;
}
}
@@ -27,6 +27,5 @@ __libpthread_freeres (void)
{
call_function_static_weak (__default_pthread_attr_freeres);
call_function_static_weak (__nptl_stacks_freeres);
- call_function_static_weak (__shm_directory_freeres);
call_function_static_weak (__nptl_unwind_freeres);
}
@@ -629,7 +629,6 @@ extern void __nptl_set_robust (struct pthread *self);
#endif
extern void __nptl_stacks_freeres (void) attribute_hidden;
-extern void __shm_directory_freeres (void) attribute_hidden;
extern void __wait_lookup_done (void) attribute_hidden;
@@ -65,7 +65,8 @@ routines := \
spawnattr_setsigmask spawnattr_setschedpolicy spawnattr_setschedparam \
posix_madvise \
get_child_max sched_cpucount sched_cpualloc sched_cpufree \
- streams-compat
+ streams-compat \
+ shm-directory
aux := init-posix environ
tests := test-errno tstgetopt testfnm runtests runptests \
@@ -150,5 +150,6 @@ libc {
GLIBC_PRIVATE {
__libc_fork; __libc_pread; __libc_pwrite;
__nanosleep_nocancel; __pause_nocancel;
+ __shm_get_name;
}
}
similarity index 60%
rename from sysdeps/posix/shm-directory.c
rename to posix/shm-directory.c
@@ -16,23 +16,31 @@
License along with the GNU C Library; if not, see
<https://www.gnu.org/licenses/>. */
-#include <shm-directory.h>
#include <unistd.h>
#if _POSIX_MAPPED_FILES
-# include <paths.h>
-
-# define SHMDIR (_PATH_DEV "shm/")
+#include <alloc_buffer.h>
+#include <shm-directory.h>
+#include <string.h>
-const char *
-__shm_directory (size_t *len)
+int
+__shm_get_name (struct shmdir_name *result, const char *name, bool sem_prefix)
{
- *len = sizeof SHMDIR - 1;
- return SHMDIR;
+ while (name[0] == '/')
+ ++name;
+ size_t namelen = strlen (name);
+
+ struct alloc_buffer buffer
+ = alloc_buffer_create (result->name, sizeof (result->name));
+ alloc_buffer_copy_bytes (&buffer, SHMDIR, strlen (SHMDIR));
+ if (sem_prefix)
+ alloc_buffer_copy_bytes (&buffer, "sem.", strlen ("sem."));
+ alloc_buffer_copy_bytes (&buffer, name, namelen + 1);
+ if (namelen == 0 || memchr (name, '/', namelen) != NULL
+ || alloc_buffer_has_failed (&buffer))
+ return -1;
+ return 0;
}
-# if IS_IN (libpthread)
-hidden_def (__shm_directory)
-# endif
#endif
deleted file mode 100644
@@ -1,30 +0,0 @@
-/* Header for directory for shm/sem files. libpthread version.
- Copyright (C) 2014-2021 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
- <https://www.gnu.org/licenses/>. */
-
-#ifndef _SHM_DIRECTORY_H
-
-#include <sysdeps/posix/shm-directory.h>
-
-/* For libpthread the __shm_directory function lives in libpthread.
- We don't want PLT calls from there. But it's also used from
- librt, so it cannot just be declared hidden. */
-
-#if IS_IN (libpthread)
-hidden_proto (__shm_directory)
-#endif
-#endif /* shm-directory.h */
@@ -3,9 +3,3 @@ L_tmpnam = 20
TMP_MAX = 238328
L_ctermid = 9
L_cuserid = 9
-
-ifeq ($(subdir)|$(have-thread-library),rt|no)
-# With NPTL, this lives in libpthread so it can be used for sem_open too.
-# Without NPTL, it's just private in librt.
-librt-routines += shm-directory
-endif
deleted file mode 100644
@@ -1,66 +0,0 @@
-/* Header for directory for shm/sem files.
- Copyright (C) 2014-2021 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
- <https://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. PREFIX is a string constant used as a
- prefix on NAME. */
-
-#define SHM_GET_NAME(errno_for_invalid, retval_for_invalid, prefix) \
- 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 + sizeof prefix - 1 + namelen); \
- __mempcpy (__mempcpy (__mempcpy (shm_name, shm_dir, shm_dirlen), \
- prefix, sizeof prefix - 1), \
- name, namelen)
-
-#endif /* shm-directory.h */
@@ -24,6 +24,7 @@
#else
+# include <errno.h>
# include <fcntl.h>
# include <pthread.h>
# include <shm-directory.h>
@@ -33,7 +34,12 @@
int
shm_open (const char *name, int oflag, mode_t mode)
{
- SHM_GET_NAME (EINVAL, -1, "");
+ struct shmdir_name dirname;
+ if (__shm_get_name (&dirname, name, false) != 0)
+ {
+ __set_errno (EINVAL);
+ return -1;
+ }
oflag |= O_NOFOLLOW | O_CLOEXEC;
@@ -41,7 +47,7 @@ shm_open (const char *name, int oflag, mode_t mode)
int state;
pthread_setcancelstate (PTHREAD_CANCEL_DISABLE, &state);
- int fd = open (shm_name, oflag, mode);
+ int fd = open (dirname.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
@@ -25,16 +25,21 @@
#include <errno.h>
#include <string.h>
-#include "shm-directory.h"
+#include <shm-directory.h>
/* Remove shared memory object. */
int
shm_unlink (const char *name)
{
- SHM_GET_NAME (ENOENT, -1, "");
-
- int result = unlink (shm_name);
+ struct shmdir_name dirname;
+ if (__shm_get_name (&dirname, name, false) != 0)
+ {
+ __set_errno (ENOENT);
+ return -1;
+ }
+
+ int result = unlink (dirname.name);
if (result < 0 && errno == EPERM)
__set_errno (EACCES);
return result;
@@ -62,8 +62,9 @@ int __sem_mappings_lock attribute_hidden = LLL_LOCK_INITIALIZER;
/* Search for existing mapping and if possible add the one provided. */
static sem_t *
-check_add_mapping (const char *name, size_t namelen, int fd, sem_t *existing)
+check_add_mapping (const char *name, int fd, sem_t *existing)
{
+ size_t namelen = strlen (name);
sem_t *result = SEM_FAILED;
/* Get the information about the file. */
@@ -150,8 +151,12 @@ sem_open (const char *name, int oflag, ...)
return SEM_FAILED;
}
- /* Create the name of the final file in local variable SHM_NAME. */
- SHM_GET_NAME (EINVAL, SEM_FAILED, SEM_SHM_PREFIX);
+ struct shmdir_name dirname;
+ if (__shm_get_name (&dirname, name, true) != 0)
+ {
+ __set_errno (EINVAL);
+ return SEM_FAILED;
+ }
/* Disable asynchronous cancellation. */
#ifdef __libc_ptf_call
@@ -164,7 +169,7 @@ sem_open (const char *name, int oflag, ...)
if ((oflag & O_CREAT) == 0 || (oflag & O_EXCL) == 0)
{
try_again:
- fd = __libc_open (shm_name,
+ fd = __libc_open (dirname.name,
(oflag & ~(O_CREAT|O_ACCMODE)) | O_NOFOLLOW | O_RDWR);
if (fd == -1)
@@ -178,13 +183,12 @@ sem_open (const char *name, int oflag, ...)
else
/* Check whether we already have this semaphore mapped and
create one if necessary. */
- result = check_add_mapping (name, namelen, fd, SEM_FAILED);
+ result = check_add_mapping (name, fd, SEM_FAILED);
}
else
{
/* We have to open a temporary file first since it must have the
correct form before we can start using it. */
- char *tmpfname;
mode_t mode;
unsigned int value;
va_list ap;
@@ -217,16 +221,11 @@ sem_open (const char *name, int oflag, ...)
memset ((char *) &sem.initsem + sizeof (struct new_sem), '\0',
sizeof (sem_t) - sizeof (struct new_sem));
- tmpfname = __alloca (shm_dirlen + sizeof SEM_SHM_PREFIX + 6);
- char *xxxxxx = __mempcpy (tmpfname, shm_dir, shm_dirlen);
-
+ char tmpfname[] = SHMDIR "sem.XXXXXX";
int retries = 0;
#define NRETRIES 50
while (1)
{
- /* Add the suffix for mktemp. */
- strcpy (xxxxxx, "XXXXXX");
-
/* We really want to use mktemp here. We cannot use mkstemp
since the file must be opened with a specific mode. The
mode cannot later be set since then we cannot apply the
@@ -244,7 +243,12 @@ sem_open (const char *name, int oflag, ...)
if (errno == EEXIST)
{
if (++retries < NRETRIES)
- continue;
+ {
+ /* Restore the six placeholder bytes before the
+ null terminator before the next attempt. */
+ memcpy (tmpfname + sizeof (tmpfname) - 7, "XXXXXX", 6);
+ continue;
+ }
__set_errno (EAGAIN);
}
@@ -265,7 +269,7 @@ sem_open (const char *name, int oflag, ...)
fd, 0)) != MAP_FAILED)
{
/* Create the file. Don't overwrite an existing file. */
- if (link (tmpfname, shm_name) != 0)
+ if (link (tmpfname, dirname.name) != 0)
{
/* Undo the mapping. */
(void) munmap (result, sizeof (sem_t));
@@ -290,7 +294,7 @@ sem_open (const char *name, int oflag, ...)
/* Insert the mapping into the search tree. This also
determines whether another thread sneaked by and already
added such a mapping despite the fact that we created it. */
- result = check_add_mapping (name, namelen, fd, result);
+ result = check_add_mapping (name, fd, result);
}
/* Now remove the temporary name. This should never fail. If
@@ -27,11 +27,15 @@
int
sem_unlink (const char *name)
{
- /* Construct the filename. */
- SHM_GET_NAME (ENOENT, -1, SEM_SHM_PREFIX);
+ struct shmdir_name dirname;
+ if (__shm_get_name (&dirname, name, true) != 0)
+ {
+ __set_errno (ENOENT);
+ return -1;
+ }
/* Now try removing it. */
- int ret = unlink (shm_name);
+ int ret = unlink (dirname.name);
if (ret < 0 && errno == EPERM)
__set_errno (EACCES);
return ret;
deleted file mode 100644
@@ -1,147 +0,0 @@
-/* Determine directory for shm/sem files. Linux version.
- Copyright (C) 2000-2021 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
- <https://www.gnu.org/licenses/>. */
-
-#include "shm-directory.h"
-
-#include <errno.h>
-#include <mntent.h>
-#include <paths.h>
-#include <stdio.h>
-#include <string.h>
-#include <sys/statfs.h>
-#include <libc-lock.h>
-#include "linux_fsinfo.h"
-
-
-/* Mount point of the shared memory filesystem. */
-static struct
-{
- char *dir;
- size_t dirlen;
-} mountpoint;
-
-/* This is the default directory. */
-static const char defaultdir[] = "/dev/shm/";
-
-/* Protect the `mountpoint' variable above. */
-__libc_once_define (static, once);
-
-
-/* Determine where the shmfs is mounted (if at all). */
-static void
-where_is_shmfs (void)
-{
- char buf[512];
- struct statfs f;
- struct mntent resmem;
- struct mntent *mp;
- FILE *fp;
-
- /* The canonical place is /dev/shm. This is at least what the
- documentation tells everybody to do. */
- if (__statfs (defaultdir, &f) == 0 && (f.f_type == SHMFS_SUPER_MAGIC
- || f.f_type == RAMFS_MAGIC))
- {
- /* It is in the normal place. */
- mountpoint.dir = (char *) defaultdir;
- mountpoint.dirlen = sizeof (defaultdir) - 1;
-
- return;
- }
-
- /* OK, do it the hard way. Look through the /proc/mounts file and if
- this does not exist through /etc/fstab to find the mount point. */
- fp = __setmntent ("/proc/mounts", "r");
- if (__glibc_unlikely (fp == NULL))
- {
- fp = __setmntent (_PATH_MNTTAB, "r");
- if (__glibc_unlikely (fp == NULL))
- /* There is nothing we can do. Blind guesses are not helpful. */
- return;
- }
-
- /* Now read the entries. */
- while ((mp = __getmntent_r (fp, &resmem, buf, sizeof buf)) != NULL)
- /* The original name is "shm" but this got changed in early Linux
- 2.4.x to "tmpfs". */
- if (strcmp (mp->mnt_type, "tmpfs") == 0
- || strcmp (mp->mnt_type, "shm") == 0)
- {
- /* Found it. There might be more than one place where the
- filesystem is mounted but one is enough for us. */
- size_t namelen;
-
- /* First make sure this really is the correct entry. At least
- some versions of the kernel give wrong information because
- of the implicit mount of the shmfs for SysV IPC. */
- if (__statfs (mp->mnt_dir, &f) != 0 || (f.f_type != SHMFS_SUPER_MAGIC
- && f.f_type != RAMFS_MAGIC))
- continue;
-
- namelen = strlen (mp->mnt_dir);
-
- if (namelen == 0)
- /* Hum, maybe some crippled entry. Keep on searching. */
- continue;
-
- mountpoint.dir = (char *) malloc (namelen + 2);
- if (mountpoint.dir != NULL)
- {
- char *cp = __mempcpy (mountpoint.dir, mp->mnt_dir, namelen);
- if (cp[-1] != '/')
- *cp++ = '/';
- *cp = '\0';
- mountpoint.dirlen = cp - mountpoint.dir;
- }
-
- break;
- }
-
- /* Close the stream. */
- __endmntent (fp);
-}
-
-
-const char *
-__shm_directory (size_t *len)
-{
- /* Determine where the shmfs is mounted. */
- __libc_once (once, where_is_shmfs);
-
- /* If we don't know the mount points there is nothing we can do. Ever. */
- if (__glibc_unlikely (mountpoint.dir == NULL))
- {
- __set_errno (ENOSYS);
- return NULL;
- }
-
- *len = mountpoint.dirlen;
- return mountpoint.dir;
-}
-#if IS_IN (libpthread)
-hidden_def (__shm_directory)
-
-/* Make sure the table is freed if we want to free everything before
- exiting. */
-void
-__shm_directory_freeres (void)
-{
- if (mountpoint.dir != defaultdir)
- free (mountpoint.dir);
-}
-#endif