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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
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@ -457,7 +457,7 @@ int ia32_setup_rt_frame(int sig, struct ksignal *ksig,
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else
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put_user_ex(0, &frame->uc.uc_flags);
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put_user_ex(0, &frame->uc.uc_link);
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err |= __compat_save_altstack(&frame->uc.uc_stack, regs->sp);
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compat_save_altstack_ex(&frame->uc.uc_stack, regs->sp);
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if (ksig->ka.sa.sa_flags & SA_RESTORER)
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restorer = ksig->ka.sa.sa_restorer;
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@ -358,7 +358,7 @@ static int __setup_rt_frame(int sig, struct ksignal *ksig,
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else
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put_user_ex(0, &frame->uc.uc_flags);
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put_user_ex(0, &frame->uc.uc_link);
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err |= __save_altstack(&frame->uc.uc_stack, regs->sp);
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save_altstack_ex(&frame->uc.uc_stack, regs->sp);
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/* Set up to return from userspace. */
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restorer = VDSO32_SYMBOL(current->mm->context.vdso, rt_sigreturn);
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@ -423,7 +423,7 @@ static int __setup_rt_frame(int sig, struct ksignal *ksig,
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else
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put_user_ex(0, &frame->uc.uc_flags);
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put_user_ex(0, &frame->uc.uc_link);
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err |= __save_altstack(&frame->uc.uc_stack, regs->sp);
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save_altstack_ex(&frame->uc.uc_stack, regs->sp);
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/* Set up to return from userspace. If provided, use a stub
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already in userspace. */
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@ -490,7 +490,7 @@ static int x32_setup_rt_frame(struct ksignal *ksig,
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else
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put_user_ex(0, &frame->uc.uc_flags);
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put_user_ex(0, &frame->uc.uc_link);
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err |= __compat_save_altstack(&frame->uc.uc_stack, regs->sp);
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compat_save_altstack_ex(&frame->uc.uc_stack, regs->sp);
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put_user_ex(0, &frame->uc.uc__pad0);
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if (ksig->ka.sa.sa_flags & SA_RESTORER) {
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@ -669,6 +669,13 @@ asmlinkage long compat_sys_sigaltstack(const compat_stack_t __user *uss_ptr,
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int compat_restore_altstack(const compat_stack_t __user *uss);
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int __compat_save_altstack(compat_stack_t __user *, unsigned long);
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#define compat_save_altstack_ex(uss, sp) do { \
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compat_stack_t __user *__uss = uss; \
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struct task_struct *t = current; \
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put_user_ex(ptr_to_compat((void __user *)t->sas_ss_sp), &__uss->ss_sp); \
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put_user_ex(sas_ss_flags(sp), &__uss->ss_flags); \
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put_user_ex(t->sas_ss_size, &__uss->ss_size); \
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} while (0);
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asmlinkage long compat_sys_sched_rr_get_interval(compat_pid_t pid,
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struct compat_timespec __user *interval);
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@ -434,6 +434,14 @@ void signals_init(void);
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int restore_altstack(const stack_t __user *);
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int __save_altstack(stack_t __user *, unsigned long);
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#define save_altstack_ex(uss, sp) do { \
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stack_t __user *__uss = uss; \
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struct task_struct *t = current; \
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put_user_ex((void __user *)t->sas_ss_sp, &__uss->ss_sp); \
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put_user_ex(sas_ss_flags(sp), &__uss->ss_flags); \
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put_user_ex(t->sas_ss_size, &__uss->ss_size); \
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} while (0);
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#ifdef CONFIG_PROC_FS
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struct seq_file;
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extern void render_sigset_t(struct seq_file *, const char *, sigset_t *);
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