[PATCH 3/3] signal(x86-64): alternative signal stack wraparound occurs

[Shi Weihua <shiwh@cn.fujitsu.com>]

Fixing alternative signal stack wraparound.

If a process uses alternative signal stack by using sigaltstack()
and that stack overflow, stack wraparound occurs.
This patch checks whether the signal frame is on the alternative
stack. If the frame is not on there, kill a signal SIGSEGV to the process forcedly
then the process will be terminated.

This patch is for x86-64,version is 2.6.23-rc8.

Signed-off-by: Shi Weihua <shiwh@cn.fujitsu.com>

diff -pur linux-2.6.23-rc8.orig/arch/x86_64/ia32/ia32_signal.c 
linux-2.6.23-rc8/arch/x86_64/ia32/ia32_signal.c
--- linux-2.6.23-rc8.orig/arch/x86_64/ia32/ia32_signal.c	2007-07-09 08:32:17.000000000 +0900
+++ linux-2.6.23-rc8/arch/x86_64/ia32/ia32_signal.c	2007-09-26 12:09:07.000000000 +0900
@@ -428,6 +428,10 @@ int ia32_setup_frame(int sig, struct k_s

 	frame = get_sigframe(ka, regs, sizeof(*frame));

+	if ((ka->sa.sa_flags & SA_ONSTACK)
+		&& (sas_ss_flags((unsigned long) frame) == 0))
+		goto give_sigsegv;
+
 	if (!access_ok(VERIFY_WRITE, frame, sizeof(*frame)))
 		goto give_sigsegv;

@@ -518,6 +522,10 @@ int ia32_setup_rt_frame(int sig, struct

 	frame = get_sigframe(ka, regs, sizeof(*frame));

+	if ((ka->sa.sa_flags & SA_ONSTACK)
+		&& (sas_ss_flags((unsigned long) frame) == 0))
+		goto give_sigsegv;
+
 	if (!access_ok(VERIFY_WRITE, frame, sizeof(*frame)))
 		goto give_sigsegv;

diff -pur linux-2.6.23-rc8.orig/arch/x86_64/kernel/signal.c linux-2.6.23-rc8/arch/x86_64/kernel/signal.c
--- linux-2.6.23-rc8.orig/arch/x86_64/kernel/signal.c	2007-09-26 09:44:09.000000000 +0900
+++ linux-2.6.23-rc8/arch/x86_64/kernel/signal.c	2007-09-26 12:09:31.000000000 +0900
@@ -235,6 +235,10 @@ static int setup_rt_frame(int sig, struc
 	} else
 		frame = get_stack(ka, regs, sizeof(struct rt_sigframe)) - 8;

+	if ((ka->sa.sa_flags & SA_ONSTACK)
+		&& (sas_ss_flags((unsigned long) frame) == 0))
+		goto give_sigsegv;
+
 	if (!access_ok(VERIFY_WRITE, frame, sizeof(*frame)))
 		goto give_sigsegv;


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