Introduce [compat_]save_altstack_ex() to unbreak x86 SMAP
For performance reasons, when SMAP is in use, SMAP is left open for an
entire put_user_try { ... } put_user_catch(); block, however, calling
__put_user() in the middle of that block will close SMAP as the
STAC..CLAC constructs intentionally do not nest.
Furthermore, using __put_user() rather than put_user_ex() here is bad
for performance.
Thus, introduce new [compat_]save_altstack_ex() helpers that replace
__[compat_]save_altstack() for x86, being currently the only
architecture which supports put_user_try { ... } put_user_catch().
Reported-by: H. Peter Anvin <hpa@linux.intel.com>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: H. Peter Anvin <hpa@linux.intel.com>
Cc: <stable@vger.kernel.org> # v3.8+
Link: http://lkml.kernel.org/n/tip-es5p6y64if71k8p5u08agv9n@git.kernel.org
diff --git a/include/linux/signal.h b/include/linux/signal.h
index d897484..2ac423b 100644
--- a/include/linux/signal.h
+++ b/include/linux/signal.h
@@ -434,6 +434,14 @@
int restore_altstack(const stack_t __user *);
int __save_altstack(stack_t __user *, unsigned long);
+#define save_altstack_ex(uss, sp) do { \
+ stack_t __user *__uss = uss; \
+ struct task_struct *t = current; \
+ put_user_ex((void __user *)t->sas_ss_sp, &__uss->ss_sp); \
+ put_user_ex(sas_ss_flags(sp), &__uss->ss_flags); \
+ put_user_ex(t->sas_ss_size, &__uss->ss_size); \
+} while (0);
+
#ifdef CONFIG_PROC_FS
struct seq_file;
extern void render_sigset_t(struct seq_file *, const char *, sigset_t *);