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author | Florian Weimer <fweimer@redhat.com> | 2021-02-03 08:55:13 -0300 |
---|---|---|
committer | Adhemerval Zanella <adhemerval.zanella@linaro.org> | 2021-02-08 14:10:42 -0300 |
commit | e9fed2438a1ff475821864f906286dc58907f06b (patch) | |
tree | 185b4a49e256ef312e65eafebf836ba17ea2ccef /sysdeps/posix | |
parent | 7f61f785f16d22f185de77086c44a88218436cfb (diff) | |
download | glibc-e9fed2438a1ff475821864f906286dc58907f06b.zip glibc-e9fed2438a1ff475821864f906286dc58907f06b.tar.gz glibc-e9fed2438a1ff475821864f906286dc58907f06b.tar.bz2 |
linux: Require /dev/shm as the shared memory file system
Previously, glibc would pick an arbitrary tmpfs file system from
/proc/mounts if /dev/shm was not available. This could lead to
an unsuitable file system being picked for the backing storage for
shm_open, sem_open, and related functions.
This patch introduces a new function, __shm_get_name, which builds
the file name under the appropriate (now hard-coded) directory. It is
called from the various shm_* and sem_* function. Unlike the
SHM_GET_NAME macro it replaces, the callers handle the return values
and errno updates. shm-directory.c is moved directly into the posix
subdirectory because it can be implemented directly using POSIX
functionality. It resides in libc because it is needed by both
librt and nptl/htl.
In the sem_open implementation, tmpfname is initialized directly
from a string constant. This happens to remove one alloca call.
Checked on x86_64-linux-gnu.
Diffstat (limited to 'sysdeps/posix')
-rw-r--r-- | sysdeps/posix/Makefile | 6 | ||||
-rw-r--r-- | sysdeps/posix/shm-directory.c | 38 | ||||
-rw-r--r-- | sysdeps/posix/shm-directory.h | 66 | ||||
-rw-r--r-- | sysdeps/posix/shm_open.c | 10 | ||||
-rw-r--r-- | sysdeps/posix/shm_unlink.c | 13 |
5 files changed, 17 insertions, 116 deletions
diff --git a/sysdeps/posix/Makefile b/sysdeps/posix/Makefile index 52f20f5..b58aa6a 100644 --- a/sysdeps/posix/Makefile +++ b/sysdeps/posix/Makefile @@ -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 diff --git a/sysdeps/posix/shm-directory.c b/sysdeps/posix/shm-directory.c deleted file mode 100644 index a0510c1..0000000 --- a/sysdeps/posix/shm-directory.c +++ /dev/null @@ -1,38 +0,0 @@ -/* Determine directory for shm/sem files. Generic POSIX 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/>. */ - -#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; -} -# if IS_IN (libpthread) -hidden_def (__shm_directory) -# endif - -#endif diff --git a/sysdeps/posix/shm-directory.h b/sysdeps/posix/shm-directory.h deleted file mode 100644 index 7254bda..0000000 --- a/sysdeps/posix/shm-directory.h +++ /dev/null @@ -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 */ diff --git a/sysdeps/posix/shm_open.c b/sysdeps/posix/shm_open.c index aabc724..1817c52 100644 --- a/sysdeps/posix/shm_open.c +++ b/sysdeps/posix/shm_open.c @@ -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 diff --git a/sysdeps/posix/shm_unlink.c b/sysdeps/posix/shm_unlink.c index f3258a0..c90b854 100644 --- a/sysdeps/posix/shm_unlink.c +++ b/sysdeps/posix/shm_unlink.c @@ -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; |