From: Alan Cox <alan@linux.intel.com>
Date: Thu, 5 Oct 2017 23:06:06 +0000 (+0100)
Subject: kernel: fix signal race
X-Git-Url: https://git.ndcode.org/public/gitweb.cgi?a=commitdiff_plain;h=5294216520f10041a55bfdb7f5e97f866e2ca359;p=FUZIX.git

kernel: fix signal race

Without this we can have the following occur

kill(pid, foo)
	queues signal processing for foo
signal(SIGFOO, SIG_IGN)
	executes pending signal and jumps to lala land
---

diff --git a/Kernel/TODO.md b/Kernel/TODO.md
index d5958715..ce1014fc 100644
--- a/Kernel/TODO.md
+++ b/Kernel/TODO.md
@@ -86,8 +86,10 @@ Other
 -----
 - [IP]	Check safety of changes to allow interrupts during swapper
 
-- [ ]	Check we don't have any races of the form
+- [x]	Check we don't have any races of the form
 	kill()
 		checks signal has handler
 	signal(x, SIG_DFL)
 		signal serviced
+
+	(We now clear the cached signal in this and the mask case)
diff --git a/Kernel/syscall_proc.c b/Kernel/syscall_proc.c
index eb37a1b1..47fd9792 100644
--- a/Kernel/syscall_proc.c
+++ b/Kernel/syscall_proc.c
@@ -476,8 +476,10 @@ arg_t _signal(void)
 	retval = (arg_t) udata.u_sigvec[sig];
 	if (sig != SIGKILL && sig != SIGSTOP)
 		udata.u_sigvec[sig] = func;
+	/* Force recalculation of signal pending in the syscall return path */
+	udata.u_cursig = 0;
 	irqrestore(irq);
-
+	
 	return (retval);
 
 nogood:
@@ -506,6 +508,8 @@ arg_t _sigdisp(void)
 		udata.u_ptab->p_held |= sigmask(sig);
 	else
 		udata.u_ptab->p_held &= ~sigmask(sig);
+	/* Force recalculation of signal pending in the syscall return path */
+	udata.u_cursig = 0;
 	return 0;
 }