From e9fed2438a1ff475821864f906286dc58907f06b Mon Sep 17 00:00:00 2001 From: Florian Weimer Date: Wed, 3 Feb 2021 08:55:13 -0300 Subject: 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. --- posix/Makefile | 3 ++- posix/Versions | 1 + posix/shm-directory.c | 46 ++++++++++++++++++++++++++++++++++++++++++++++ 3 files changed, 49 insertions(+), 1 deletion(-) create mode 100644 posix/shm-directory.c (limited to 'posix') diff --git a/posix/Makefile b/posix/Makefile index 956ef7d397..f54015b9a8 100644 --- a/posix/Makefile +++ b/posix/Makefile @@ -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 \ diff --git a/posix/Versions b/posix/Versions index 7d06a6d0c0..cfd3819966 100644 --- a/posix/Versions +++ b/posix/Versions @@ -150,5 +150,6 @@ libc { GLIBC_PRIVATE { __libc_fork; __libc_pread; __libc_pwrite; __nanosleep_nocancel; __pause_nocancel; + __shm_get_name; } } diff --git a/posix/shm-directory.c b/posix/shm-directory.c new file mode 100644 index 0000000000..c06bf96aa7 --- /dev/null +++ b/posix/shm-directory.c @@ -0,0 +1,46 @@ +/* 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 + . */ + +#include + +#if _POSIX_MAPPED_FILES + +#include +#include +#include + +int +__shm_get_name (struct shmdir_name *result, const char *name, bool sem_prefix) +{ + 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; +} + +#endif -- cgit 1.4.1