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Make macOS semaphore names more unique, improve assertion

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On macOS, semaphore names are global and processes can open semaphores of other processes by using their name. It was possible that multiple client/server processes randomly tried to create semaphores with the same memory address, which would cause them to have the same name. In that case, `sem_open` would fail because `O_EXCL` prevents creating semaphores if the name is already used.

This is made more unlikely by also including the PID in the semaphore name. Additionally, the semaphore name is prefixed with `/` to more closely follow the construction rules for semaphore names. In particular, the behavior is implementation-defined if the name is not prefixed with a slash.

See https://pubs.opengroup.org/onlinepubs/9799919799/functions/sem_open.html

Closes #8773.

More details are added to the assertion error message in case this does not end up fixing the issue.
This commit is contained in:
Robert Müller 2024-08-20 19:53:08 +02:00
parent 580b2690a0
commit 839c511af4
1 changed files with 10 additions and 5 deletions
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15
src/base/system.cpp
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@ -867,10 +867,15 @@ void sphore_destroy(SEMAPHORE *sem)
#elif defined(CONF_PLATFORM_MACOS)
void sphore_init(SEMAPHORE *sem)
{
char aBuf[32];
str_format(aBuf, sizeof(aBuf), "%p", (void *)sem);
char aBuf[64];
str_format(aBuf, sizeof(aBuf), "/%d.%p", pid(), (void *)sem);
*sem = sem_open(aBuf, O_CREAT | O_EXCL, S_IRWXU | S_IRWXG, 0);
dbg_assert(*sem != SEM_FAILED, "sem_open failure");
if(*sem == SEM_FAILED)
{
char aError[128];
str_format(aError, sizeof(aError), "sem_open failure, errno=%d, name='%s'", errno, aBuf);
dbg_assert(false, aError);
}
}
void sphore_wait(SEMAPHORE *sem)
{
@ -888,8 +893,8 @@ void sphore_signal(SEMAPHORE *sem)
void sphore_destroy(SEMAPHORE *sem)
{
dbg_assert(sem_close(*sem) == 0, "sem_close failure");
char aBuf[32];
str_format(aBuf, sizeof(aBuf), "%p", (void *)sem);
char aBuf[64];
str_format(aBuf, sizeof(aBuf), "/%d.%p", pid(), (void *)sem);
dbg_assert(sem_unlink(aBuf) == 0, "sem_unlink failure");
}
#elif defined(CONF_FAMILY_UNIX)