[S390] Protect against sigaltstack wraparound.

This is just a port of 83bd01024b1fdfc41d9b758e5669e80fca72df66
"x86: protect against sigaltstack wraparound".

Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
Signed-off-by: Heiko Carstens <heiko.carstens@de.ibm.com>

2 files changed, 20 insertions, 0 deletions

diff --git a/arch/s390/kernel/compat_signal.c b/arch/s390/kernel/compat_signal.c
index a5692c460bad..ae2f2d313930 100644
--- a/arch/s390/kernel/compat_signal.c
+++ b/arch/s390/kernel/compat_signal.c
@@ -428,6 +428,10 @@ get_sigframe(struct k_sigaction *ka, struct pt_regs * regs, size_t frame_size)
         /* Default to using normal stack */
         sp = (unsigned long) A(regs->gprs[15]);
 
+        /* Overflow on alternate signal stack gives SIGSEGV. */
+        if (on_sig_stack(sp) && !on_sig_stack((sp - frame_size) & -8UL))
+                return (void __user *) -1UL;
+
         /* This is the X/Open sanctioned signal stack switching.  */
         if (ka->sa.sa_flags & SA_ONSTACK) {
                 if (! sas_ss_flags(sp))
@@ -461,6 +465,9 @@ static int setup_frame32(int sig, struct k_sigaction *ka,
         if (!access_ok(VERIFY_WRITE, frame, sizeof(sigframe32)))
                 goto give_sigsegv;
 
+        if (frame == (void __user *) -1UL)
+                goto give_sigsegv;
+
         if (__copy_to_user(&frame->sc.oldmask, &set->sig, _SIGMASK_COPY_SIZE32))
                 goto give_sigsegv;
 
@@ -514,6 +521,9 @@ static int setup_rt_frame32(int sig, struct k_sigaction *ka, siginfo_t *info,
         if (!access_ok(VERIFY_WRITE, frame, sizeof(rt_sigframe32)))
                 goto give_sigsegv;
 
+        if (frame == (void __user *) -1UL)
+                goto give_sigsegv;
+
         if (copy_siginfo_to_user32(&frame->info, info))
                 goto give_sigsegv;
 
diff --git a/arch/s390/kernel/signal.c b/arch/s390/kernel/signal.c
index 4449bf32cbf1..8c92191949c2 100644
--- a/arch/s390/kernel/signal.c
+++ b/arch/s390/kernel/signal.c
@@ -235,6 +235,10 @@ get_sigframe(struct k_sigaction *ka, struct pt_regs * regs, size_t frame_size)
         /* Default to using normal stack */
         sp = regs->gprs[15];
 
+        /* Overflow on alternate signal stack gives SIGSEGV. */
+        if (on_sig_stack(sp) && !on_sig_stack((sp - frame_size) & -8UL))
+                return (void __user *) -1UL;
+
         /* This is the X/Open sanctioned signal stack switching.  */
         if (ka->sa.sa_flags & SA_ONSTACK) {
                 if (! sas_ss_flags(sp))
@@ -270,6 +274,9 @@ static int setup_frame(int sig, struct k_sigaction *ka,
         if (!access_ok(VERIFY_WRITE, frame, sizeof(sigframe)))
                 goto give_sigsegv;
 
+        if (frame == (void __user *) -1UL)
+                goto give_sigsegv;
+
         if (__copy_to_user(&frame->sc.oldmask, &set->sig, _SIGMASK_COPY_SIZE))
                 goto give_sigsegv;
 
@@ -327,6 +334,9 @@ static int setup_rt_frame(int sig, struct k_sigaction *ka, siginfo_t *info,
         if (!access_ok(VERIFY_WRITE, frame, sizeof(rt_sigframe)))
                 goto give_sigsegv;
 
+        if (frame == (void __user *) -1UL)
+                goto give_sigsegv;
+
         if (copy_siginfo_to_user(&frame->info, info))
                 goto give_sigsegv;