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. --- sysdeps/pthread/sem_unlink.c | 10 +++++++--- 1 file changed, 7 insertions(+), 3 deletions(-) (limited to 'sysdeps/pthread/sem_unlink.c') diff --git a/sysdeps/pthread/sem_unlink.c b/sysdeps/pthread/sem_unlink.c index faafbe4e91..1f06a55b8e 100644 --- a/sysdeps/pthread/sem_unlink.c +++ b/sysdeps/pthread/sem_unlink.c @@ -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; -- cgit 1.4.1