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Kernel: Support null act argument for sigaction syscall

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Userspace can provide a null argument for the `act` argument to the
`sigaction` syscall to not set any new behavior. This is described
here:

https://pubs.opengroup.org/onlinepubs/007904875/functions/sigaction.html

Without this fix, the `copy_from_user(...)` invocation on `user_act`
fails and makes the syscall return early.
This commit is contained in:
Jelle Raaijmakers 2021-04-24 02:17:22 +02:00 committed by Andreas Kling
parent 0ad29bc3c9
commit 54f5b1346c
1 changed files with 7 additions and 6 deletions
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13
Kernel/Syscalls/sigaction.cpp
View file

@ -55,10 +55,6 @@ KResultOr<int> Process::sys$sigaction(int signum, Userspace<const sigaction*> us
if (signum < 1 || signum >= 32 || signum == SIGKILL || signum == SIGSTOP)
return EINVAL;
sigaction act {};
if (!copy_from_user(&act, user_act))
return EFAULT;
InterruptDisabler disabler; // FIXME: This should use a narrower lock. Maybe a way to ignore signals temporarily?
auto& action = Thread::current()->m_signal_action_data[signum];
if (user_old_act) {
@ -68,8 +64,13 @@ KResultOr<int> Process::sys$sigaction(int signum, Userspace<const sigaction*> us
if (!copy_to_user(user_old_act, &old_act))
return EFAULT;
}
action.flags = act.sa_flags;
action.handler_or_sigaction = VirtualAddress { reinterpret_cast<void*>(act.sa_sigaction) };
if (user_act) {
sigaction act {};
if (!copy_from_user(&act, user_act))
return EFAULT;
action.flags = act.sa_flags;
action.handler_or_sigaction = VirtualAddress { reinterpret_cast<void*>(act.sa_sigaction) };
}
return 0;
}