Commit-ID: bd1c149aa9915b9abb6d83d0f01dfd2ace0680b5
Gitweb: http://git.kernel.org/tip/bd1c149aa9915b9abb6d83d0f01dfd2ace0680b5
Author: Al Viro <[email protected]>
AuthorDate: Sun, 1 Sep 2013 20:35:01 +0100
Committer: H. Peter Anvin <[email protected]>
CommitDate: Sun, 1 Sep 2013 14:16:33 -0700
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 <[email protected]>
Signed-off-by: Al Viro <[email protected]>
Signed-off-by: H. Peter Anvin <[email protected]>
Cc: <[email protected]> # v3.8+
Link: http://lkml.kernel.org/n/[email protected]
---
arch/x86/ia32/ia32_signal.c | 2 +-
arch/x86/kernel/signal.c | 6 +++---
include/linux/compat.h | 7 +++++++
include/linux/signal.h | 8 ++++++++
4 files changed, 19 insertions(+), 4 deletions(-)
diff --git a/arch/x86/ia32/ia32_signal.c b/arch/x86/ia32/ia32_signal.c
index bccfca6..665a730 100644
--- a/arch/x86/ia32/ia32_signal.c
+++ b/arch/x86/ia32/ia32_signal.c
@@ -457,7 +457,7 @@ int ia32_setup_rt_frame(int sig, struct ksignal *ksig,
else
put_user_ex(0, &frame->uc.uc_flags);
put_user_ex(0, &frame->uc.uc_link);
- err |= __compat_save_altstack(&frame->uc.uc_stack, regs->sp);
+ compat_save_altstack_ex(&frame->uc.uc_stack, regs->sp);
if (ksig->ka.sa.sa_flags & SA_RESTORER)
restorer = ksig->ka.sa.sa_restorer;
diff --git a/arch/x86/kernel/signal.c b/arch/x86/kernel/signal.c
index cf91358..d859eea 100644
--- a/arch/x86/kernel/signal.c
+++ b/arch/x86/kernel/signal.c
@@ -358,7 +358,7 @@ static int __setup_rt_frame(int sig, struct ksignal *ksig,
else
put_user_ex(0, &frame->uc.uc_flags);
put_user_ex(0, &frame->uc.uc_link);
- err |= __save_altstack(&frame->uc.uc_stack, regs->sp);
+ save_altstack_ex(&frame->uc.uc_stack, regs->sp);
/* Set up to return from userspace. */
restorer = VDSO32_SYMBOL(current->mm->context.vdso,
rt_sigreturn);
@@ -423,7 +423,7 @@ static int __setup_rt_frame(int sig, struct ksignal *ksig,
else
put_user_ex(0, &frame->uc.uc_flags);
put_user_ex(0, &frame->uc.uc_link);
- err |= __save_altstack(&frame->uc.uc_stack, regs->sp);
+ save_altstack_ex(&frame->uc.uc_stack, regs->sp);
/* Set up to return from userspace. If provided, use a stub
already in userspace. */
@@ -490,7 +490,7 @@ static int x32_setup_rt_frame(struct ksignal *ksig,
else
put_user_ex(0, &frame->uc.uc_flags);
put_user_ex(0, &frame->uc.uc_link);
- err |= __compat_save_altstack(&frame->uc.uc_stack, regs->sp);
+ compat_save_altstack_ex(&frame->uc.uc_stack, regs->sp);
put_user_ex(0, &frame->uc.uc__pad0);
if (ksig->ka.sa.sa_flags & SA_RESTORER) {
diff --git a/include/linux/compat.h b/include/linux/compat.h
index 7f0c1dd..ec1aee4 100644
--- a/include/linux/compat.h
+++ b/include/linux/compat.h
@@ -669,6 +669,13 @@ asmlinkage long compat_sys_sigaltstack(const
compat_stack_t __user *uss_ptr,
int compat_restore_altstack(const compat_stack_t __user *uss);
int __compat_save_altstack(compat_stack_t __user *, unsigned long);
+#define compat_save_altstack_ex(uss, sp) do { \
+ compat_stack_t __user *__uss = uss; \
+ struct task_struct *t = current; \
+ put_user_ex(ptr_to_compat((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);
asmlinkage long compat_sys_sched_rr_get_interval(compat_pid_t pid,
struct compat_timespec __user
*interval);
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 @@ void signals_init(void);
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 *);
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