From bf2c51426dc4c8b528e6f2efff4aaca8c9430317 Mon Sep 17 00:00:00 2001
From: "K. Lange" <klange@toaruos.org>
Date: Sat, 29 Oct 2022 17:27:05 +0900
Subject: [PATCH] kernel: proc->group may have exited

Handling of thread parents needs to be better... the initial thread
of a process can disappear, and with pid reuse it could even be
replaced by a different process... this needs to be cleaned up more.
---
 kernel/arch/x86_64/idt.c | 8 +++++---
 kernel/sys/syscall.c     | 3 +++
 2 files changed, 8 insertions(+), 3 deletions(-)

diff --git a/kernel/arch/x86_64/idt.c b/kernel/arch/x86_64/idt.c
index ba4ee88b..62bae8d6 100644
--- a/kernel/arch/x86_64/idt.c
+++ b/kernel/arch/x86_64/idt.c
@@ -357,7 +357,7 @@ void arch_dump_traceback(void) {
  *
  * @param fromAddr The low address to map, should be page aligned.
  */
-static void map_more_stack(uintptr_t fromAddr) {
+static int map_more_stack(uintptr_t fromAddr) {
 	volatile process_t * volatile proc = this_core->current_process;
 
 	/* Is this thread the process leader? */
@@ -365,6 +365,8 @@ static void map_more_stack(uintptr_t fromAddr) {
 		proc = process_from_pid(proc->group);
 	}
 
+	if (!proc) return 0;
+
 	/* Make sure nothing else is going to mess with this process's page tables */
 	spin_lock(proc->image.lock);
 
@@ -378,6 +380,7 @@ static void map_more_stack(uintptr_t fromAddr) {
 	proc->image.userstack = fromAddr;
 
 	spin_unlock(proc->image.lock);
+	return 1;
 }
 
 /**
@@ -520,8 +523,7 @@ static void _page_fault(struct regs * r) {
 
 	/* Quietly map more stack if it was a viable stack address. */
 	if (faulting_address < 0x800000000000 && faulting_address > 0x700000000000) {
-		map_more_stack(faulting_address & 0xFFFFffffFFFFf000);
-		return;
+		if (map_more_stack(faulting_address & 0xFFFFffffFFFFf000)) return;
 	}
 
 	/* Otherwise, segfault the current process. */
diff --git a/kernel/sys/syscall.c b/kernel/sys/syscall.c
index e012a371..f9b4159d 100644
--- a/kernel/sys/syscall.c
+++ b/kernel/sys/syscall.c
@@ -55,6 +55,7 @@ long sys_sbrk(ssize_t size) {
 	if (proc->group != 0) {
 		proc = process_from_pid(proc->group);
 	}
+	if (!proc) return -EINVAL;
 	spin_lock(proc->image.lock);
 	uintptr_t out = proc->image.heap;
 	for (uintptr_t i = out; i < out + size; i += 0x1000) {
@@ -135,6 +136,7 @@ long sys_sysfunc(long fn, char ** args) {
 			if (!args[0]) return -EFAULT;
 			volatile process_t * volatile proc = this_core->current_process;
 			if (proc->group != 0) proc = process_from_pid(proc->group);
+			if (!proc) return -EFAULT;
 			spin_lock(proc->image.lock);
 			proc->image.heap = (uintptr_t)args[0];
 			spin_unlock(proc->image.lock);
@@ -149,6 +151,7 @@ long sys_sysfunc(long fn, char ** args) {
 			if (!args) return -EFAULT;
 			volatile process_t * volatile proc = this_core->current_process;
 			if (proc->group != 0) proc = process_from_pid(proc->group);
+			if (!proc) return -EFAULT;
 			spin_lock(proc->image.lock);
 			/* Align inputs */
 			uintptr_t start = ((uintptr_t)args[0]) & 0xFFFFffffFFFFf000UL;