libselinux: Do not clobber errno of the world #445
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libselinux clobbers errno of all consumers (systemd, sshd you name it)
because its constructors do not properly save and restore errno.
The following program demonstrates it.
int main(void)
{
assert(errno == 0);
/* Just a test, it doesn't matter already clobbered */
if(is_selinux_enabled() < 0) {
perror("not enabled");
return 1;
}
}
if any function sets errno, it is not switched back to the original
value and standards DO NOT require errno to the set to zero before
entering main
Signed-off-by: Cristian Rodríguez <cristian@rodriguez.im>
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standards do not require errno to be reset to zero before entering main, third party libraries like openssl and libcap(1) use ELF constructors that if buggy (1) will clobber errno value to everybody else. Libselinux also clobbers errno in most tests cases (2) ensure that is set to zero before starting. (1) https://git.kernel.org/pub/scm/libs/libcap/libcap.git/commit/?id=f25a1b7e69f7b33e6afb58b3e38f3450b7d2d9a0 (2) SELinuxProject/selinux#445
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Seems fine, just a nit: the identifier Also the main way of contribution is to send patches via |
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libselinux clobbers errno of all consumers (systemd, sshd you name it) because its constructors do not properly save and restore errno. The following program demonstrates it.
int main(void)
{
assert(errno == 0);
/* Just a test, it doesn't matter already clobbered */
if(is_selinux_enabled() < 0) {
perror("not enabled");
return 1;
}
}
if any function sets errno, it is not switched back to the original value and standards DO NOT require errno to the set to zero before entering main