Commit c5c87812 authored by Gabriel Krisman Bertazi's avatar Gabriel Krisman Bertazi Committed by Thomas Gleixner
Browse files

x86: vdso: Expose sigreturn address on vdso to the kernel 



Syscall user redirection requires the signal trampoline code to not be
captured, in order to support returning with a locked selector while
avoiding recursion back into the signal handler.  For ia-32, which has
the trampoline in the vDSO, expose the entry points to the kernel, such
that it can avoid dispatching syscalls from that region to userspace.

Suggested-by: default avatarAndy Lutomirski <luto@kernel.org>
Signed-off-by: default avatarGabriel Krisman Bertazi <krisman@collabora.com>
Signed-off-by: default avatarThomas Gleixner <tglx@linutronix.de>
Reviewed-by: default avatarKees Cook <keescook@chromium.org>
Reviewed-by: default avatarAndy Lutomirski <luto@kernel.org>
Acked-by: default avatarAndy Lutomirski <luto@kernel.org>
Acked-by: default avatarPeter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lore.kernel.org/r/20201127193238.821364-2-krisman@collabora.com
parent 01fe185d

arch/x86/entry/vdso/vdso2c.c

+2 −0
Original line number Diff line number Diff line
@@ -101,6 +101,8 @@ struct vdso_sym required_syms[] = { 
	{"__kernel_sigreturn", true},

	{"__kernel_rt_sigreturn", true},

	{"int80_landing_pad", true},

	{"vdso32_rt_sigreturn_landing_pad", true},

	{"vdso32_sigreturn_landing_pad", true},

};



__attribute__((format(printf, 1, 2))) __attribute__((noreturn))

arch/x86/entry/vdso/vdso32/sigreturn.S

+2 −0
Original line number Diff line number Diff line
@@ -18,6 +18,7 @@ __kernel_sigreturn: 
	movl $__NR_sigreturn, %eax

	SYSCALL_ENTER_KERNEL

.LEND_sigreturn:

SYM_INNER_LABEL(vdso32_sigreturn_landing_pad, SYM_L_GLOBAL)

	nop

	.size __kernel_sigreturn,.-.LSTART_sigreturn
@@ -29,6 +30,7 @@ __kernel_rt_sigreturn: 
	movl $__NR_rt_sigreturn, %eax

	SYSCALL_ENTER_KERNEL

.LEND_rt_sigreturn:

SYM_INNER_LABEL(vdso32_rt_sigreturn_landing_pad, SYM_L_GLOBAL)

	nop

	.size __kernel_rt_sigreturn,.-.LSTART_rt_sigreturn

	.previous

arch/x86/entry/vdso/vma.c

+15 −0
Original line number Diff line number Diff line
@@ -436,6 +436,21 @@ int arch_setup_additional_pages(struct linux_binprm *bprm, int uses_interp) 
}

#endif



bool arch_syscall_is_vdso_sigreturn(struct pt_regs *regs)

{

#if defined(CONFIG_X86_32) || defined(CONFIG_IA32_EMULATION)

	const struct vdso_image *image = current->mm->context.vdso_image;

	unsigned long vdso = (unsigned long) current->mm->context.vdso;



	if (in_ia32_syscall() && image == &vdso_image_32) {

		if (regs->ip == vdso + image->sym_vdso32_sigreturn_landing_pad ||

		    regs->ip == vdso + image->sym_vdso32_rt_sigreturn_landing_pad)

			return true;

	}

#endif

	return false;

}



#ifdef CONFIG_X86_64

static __init int vdso_setup(char *s)

{

arch/x86/include/asm/elf.h

+2 −0
Original line number Diff line number Diff line
@@ -388,6 +388,8 @@ extern int compat_arch_setup_additional_pages(struct linux_binprm *bprm, 
	compat_arch_setup_additional_pages(bprm, interpreter,		\

					   (ex->e_machine == EM_X86_64))



extern bool arch_syscall_is_vdso_sigreturn(struct pt_regs *regs);



/* Do not change the values. See get_align_mask() */

enum align_flags {

	ALIGN_VA_32	= BIT(0),

arch/x86/include/asm/vdso.h

+2 −0
Original line number Diff line number Diff line
@@ -27,6 +27,8 @@ struct vdso_image { 
	long sym___kernel_rt_sigreturn;

	long sym___kernel_vsyscall;

	long sym_int80_landing_pad;

	long sym_vdso32_sigreturn_landing_pad;

	long sym_vdso32_rt_sigreturn_landing_pad;

};



#ifdef CONFIG_X86_64

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