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Commit 230e51f2 authored by Linus Torvalds's avatar Linus Torvalds
Browse files

Merge branch 'core-signals-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip 

Pull core signal updates from Ingo Molnar:
 "These updates from Stas Sergeev and Andy Lutomirski, improve the
  sigaltstack interface by extending its ABI with the SS_AUTODISARM
  feature, which makes it possible to use swapcontext() in a sighandler
  that works on sigaltstack.  Without this flag, the subsequent signal
  will corrupt the state of the switched-away sighandler.

  The inspiration is more robust dosemu signal handling"

* 'core-signals-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  signals/sigaltstack: Change SS_AUTODISARM to (1U << 31)
  signals/sigaltstack: Report current flag bits in sigaltstack()
  selftests/sigaltstack: Fix the sigaltstack test on old kernels
  signals/sigaltstack: If SS_AUTODISARM, bypass on_sig_stack()
  selftests/sigaltstack: Add new testcase for sigaltstack(SS_ONSTACK|SS_AUTODISARM)
  signals/sigaltstack: Implement SS_AUTODISARM flag
  signals/sigaltstack: Prepare to add new SS_xxx flags
  signals/sigaltstack, x86/signals: Unify the x86 sigaltstack check with other architectures
parents a3871bd4 91c61805

arch/x86/kernel/signal.c

+11 −12
Original line number Diff line number Diff line
@@ -248,19 +248,18 @@ get_sigframe(struct k_sigaction *ka, struct pt_regs *regs, size_t frame_size, 
	if (config_enabled(CONFIG_X86_64))

		sp -= 128;



	if (!onsigstack) {

	/* This is the X/Open sanctioned signal stack switching.  */

	if (ka->sa.sa_flags & SA_ONSTACK) {

			if (current->sas_ss_size)

		if (sas_ss_flags(sp) == 0)

			sp = current->sas_ss_sp + current->sas_ss_size;

	} else if (config_enabled(CONFIG_X86_32) &&

		   !onsigstack &&

		   (regs->ss & 0xffff) != __USER_DS &&

		   !(ka->sa.sa_flags & SA_RESTORER) &&

		   ka->sa.sa_restorer) {

		/* This is the legacy signal stack switching. */

		sp = (unsigned long) ka->sa.sa_restorer;

	}

	}



	if (fpu->fpstate_active) {

		sp = fpu__alloc_mathframe(sp, config_enabled(CONFIG_X86_32),

include/linux/sched.h

+20 −0
Original line number Diff line number Diff line
@@ -1595,6 +1595,7 @@ struct task_struct { 


	unsigned long sas_ss_sp;

	size_t sas_ss_size;

	unsigned sas_ss_flags;



	struct callback_head *task_works;
@@ -2574,6 +2575,18 @@ static inline int kill_cad_pid(int sig, int priv) 
 */

static inline int on_sig_stack(unsigned long sp)

{

	/*

	 * If the signal stack is SS_AUTODISARM then, by construction, we

	 * can't be on the signal stack unless user code deliberately set

	 * SS_AUTODISARM when we were already on it.

	 *

	 * This improves reliability: if user state gets corrupted such that

	 * the stack pointer points very close to the end of the signal stack,

	 * then this check will enable the signal to be handled anyway.

	 */

	if (current->sas_ss_flags & SS_AUTODISARM)

		return 0;



#ifdef CONFIG_STACK_GROWSUP

	return sp >= current->sas_ss_sp &&

		sp - current->sas_ss_sp < current->sas_ss_size;
@@ -2591,6 +2604,13 @@ static inline int sas_ss_flags(unsigned long sp) 
	return on_sig_stack(sp) ? SS_ONSTACK : 0;

}



static inline void sas_ss_reset(struct task_struct *p)

{

	p->sas_ss_sp = 0;

	p->sas_ss_size = 0;

	p->sas_ss_flags = SS_DISABLE;

}



static inline unsigned long sigsp(unsigned long sp, struct ksignal *ksig)

{

	if (unlikely((ksig->ka.sa.sa_flags & SA_ONSTACK)) && ! sas_ss_flags(sp))

include/linux/signal.h

+3 −1
Original line number Diff line number Diff line
@@ -432,8 +432,10 @@ int __save_altstack(stack_t __user *, unsigned long); 
	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_flags, &__uss->ss_flags); \

	put_user_ex(t->sas_ss_size, &__uss->ss_size); \

	if (t->sas_ss_flags & SS_AUTODISARM) \

		sas_ss_reset(t); \

} while (0);



#ifdef CONFIG_PROC_FS

include/uapi/linux/signal.h

+5 −0
Original line number Diff line number Diff line
@@ -7,4 +7,9 @@ 
#define SS_ONSTACK	1

#define SS_DISABLE	2



/* bit-flags */

#define SS_AUTODISARM	(1U << 31)	/* disable sas during sighandling */

/* mask for all SS_xxx flags */

#define SS_FLAG_BITS	SS_AUTODISARM



#endif /* _UAPI_LINUX_SIGNAL_H */

kernel/fork.c

+1 −1
Original line number Diff line number Diff line
@@ -1494,7 +1494,7 @@ static struct task_struct *copy_process(unsigned long clone_flags, 
	 * sigaltstack should be cleared when sharing the same VM

	 */

	if ((clone_flags & (CLONE_VM|CLONE_VFORK)) == CLONE_VM)

		p->sas_ss_sp = p->sas_ss_size = 0;

		sas_ss_reset(p);



	/*

	 * Syscall tracing and stepping should be turned off in the