generic compat_sys_sigaltstack()

Again, conditional on CONFIG_GENERIC_SIGALTSTACK

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

1 files changed, 45 insertions, 0 deletions

diff --git a/kernel/signal.c b/kernel/signal.c
index f05f4c4150d9..aee85bd76b8a 100644
--- a/kernel/signal.c
+++ b/kernel/signal.c
@@ -31,6 +31,7 @@
 #include <linux/nsproxy.h>
 #include <linux/user_namespace.h>
 #include <linux/uprobes.h>
+#include <linux/compat.h>
 #define CREATE_TRACE_POINTS
 #include <trace/events/signal.h>
 
@@ -3116,6 +3117,50 @@ int restore_altstack(const stack_t __user *uss)
         return err == -EFAULT ? err : 0;
 }
 
+#ifdef CONFIG_COMPAT
+#ifdef CONFIG_GENERIC_SIGALTSTACK
+asmlinkage long compat_sys_sigaltstack(const compat_stack_t __user *uss_ptr,
+                                       compat_stack_t __user *uoss_ptr)
+{
+        stack_t uss, uoss;
+        int ret;
+        mm_segment_t seg;
+
+        if (uss_ptr) {
+                compat_stack_t uss32;
+
+                memset(&uss, 0, sizeof(stack_t));
+                if (copy_from_user(&uss32, uss_ptr, sizeof(compat_stack_t)))
+                        return -EFAULT;
+                uss.ss_sp = compat_ptr(uss32.ss_sp);
+                uss.ss_flags = uss32.ss_flags;
+                uss.ss_size = uss32.ss_size;
+        }
+        seg = get_fs();
+        set_fs(KERNEL_DS);
+        ret = do_sigaltstack((stack_t __force __user *) (uss_ptr ? &uss : NULL),
+                             (stack_t __force __user *) &uoss,
+                             compat_user_stack_pointer());
+        set_fs(seg);
+        if (ret >= 0 && uoss_ptr)  {
+                if (!access_ok(VERIFY_WRITE, uoss_ptr, sizeof(compat_stack_t)) ||
+                    __put_user(ptr_to_compat(uoss.ss_sp), &uoss_ptr->ss_sp) ||
+                    __put_user(uoss.ss_flags, &uoss_ptr->ss_flags) ||
+                    __put_user(uoss.ss_size, &uoss_ptr->ss_size))
+                        ret = -EFAULT;
+        }
+        return ret;
+}
+
+int compat_restore_altstack(const compat_stack_t __user *uss)
+{
+        int err = compat_sys_sigaltstack(uss, NULL);
+        /* squash all but -EFAULT for now */
+        return err == -EFAULT ? err : 0;
+}
+#endif
+#endif
+
 #ifdef __ARCH_WANT_SYS_SIGPENDING
 
 /**