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Commit f56141e3 authored by Andy Lutomirski's avatar Andy Lutomirski Committed by Linus Torvalds
Browse files

all arches, signal: move restart_block to struct task_struct 



If an attacker can cause a controlled kernel stack overflow, overwriting
the restart block is a very juicy exploit target.  This is because the
restart_block is held in the same memory allocation as the kernel stack.

Moving the restart block to struct task_struct prevents this exploit by
making the restart_block harder to locate.

Note that there are other fields in thread_info that are also easy
targets, at least on some architectures.

It's also a decent simplification, since the restart code is more or less
identical on all architectures.

[james.hogan@imgtec.com: metag: align thread_info::supervisor_stack]
Signed-off-by: default avatarAndy Lutomirski <luto@amacapital.net>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Kees Cook <keescook@chromium.org>
Cc: David Miller <davem@davemloft.net>
Acked-by: default avatarRichard Weinberger <richard@nod.at>
Cc: Richard Henderson <rth@twiddle.net>
Cc: Ivan Kokshaysky <ink@jurassic.park.msu.ru>
Cc: Matt Turner <mattst88@gmail.com>
Cc: Vineet Gupta <vgupta@synopsys.com>
Cc: Russell King <rmk@arm.linux.org.uk>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Will Deacon <will.deacon@arm.com>
Cc: Haavard Skinnemoen <hskinnemoen@gmail.com>
Cc: Hans-Christian Egtvedt <egtvedt@samfundet.no>
Cc: Steven Miao <realmz6@gmail.com>
Cc: Mark Salter <msalter@redhat.com>
Cc: Aurelien Jacquiot <a-jacquiot@ti.com>
Cc: Mikael Starvik <starvik@axis.com>
Cc: Jesper Nilsson <jesper.nilsson@axis.com>
Cc: David Howells <dhowells@redhat.com>
Cc: Richard Kuo <rkuo@codeaurora.org>
Cc: "Luck, Tony" <tony.luck@intel.com>
Cc: Geert Uytterhoeven <geert@linux-m68k.org>
Cc: Michal Simek <monstr@monstr.eu>
Cc: Ralf Baechle <ralf@linux-mips.org>
Cc: Jonas Bonn <jonas@southpole.se>
Cc: "James E.J. Bottomley" <jejb@parisc-linux.org>
Cc: Helge Deller <deller@gmx.de>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: Paul Mackerras <paulus@samba.org>
Acked-by: Michael Ellerman <mpe@ellerman.id.au> (powerpc)
Tested-by: Michael Ellerman <mpe@ellerman.id.au> (powerpc)
Cc: Martin Schwidefsky <schwidefsky@de.ibm.com>
Cc: Heiko Carstens <heiko.carstens@de.ibm.com>
Cc: Chen Liqin <liqin.linux@gmail.com>
Cc: Lennox Wu <lennox.wu@gmail.com>
Cc: Chris Metcalf <cmetcalf@ezchip.com>
Cc: Guan Xuetao <gxt@mprc.pku.edu.cn>
Cc: Chris Zankel <chris@zankel.net>
Cc: Max Filippov <jcmvbkbc@gmail.com>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Guenter Roeck <linux@roeck-us.net>
Signed-off-by: default avatarJames Hogan <james.hogan@imgtec.com>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent edc924e0

arch/alpha/include/asm/thread_info.h

+0 −5
Original line number Diff line number Diff line
@@ -27,8 +27,6 @@ struct thread_info { 
	int bpt_nsaved;

	unsigned long bpt_addr[2];		/* breakpoint handling  */

	unsigned int bpt_insn[2];



	struct restart_block	restart_block;

};



/*
@@ -40,9 +38,6 @@ struct thread_info { 
	.exec_domain	= &default_exec_domain,	\

	.addr_limit	= KERNEL_DS,		\

	.preempt_count	= INIT_PREEMPT_COUNT,	\

	.restart_block = {			\

		.fn = do_no_restart_syscall,	\

	},					\

}



#define init_thread_info	(init_thread_union.thread_info)

arch/alpha/kernel/signal.c

+1 −1
Original line number Diff line number Diff line
@@ -150,7 +150,7 @@ restore_sigcontext(struct sigcontext __user *sc, struct pt_regs *regs) 
	struct switch_stack *sw = (struct switch_stack *)regs - 1;

	long i, err = __get_user(regs->pc, &sc->sc_pc);



	current_thread_info()->restart_block.fn = do_no_restart_syscall;

	current->restart_block.fn = do_no_restart_syscall;



	sw->r26 = (unsigned long) ret_from_sys_call;

arch/arc/include/asm/thread_info.h

+0 −4
Original line number Diff line number Diff line
@@ -46,7 +46,6 @@ struct thread_info { 
	struct exec_domain *exec_domain;/* execution domain */

	__u32 cpu;			/* current CPU */

	unsigned long thr_ptr;		/* TLS ptr */

	struct restart_block restart_block;

};



/*
@@ -62,9 +61,6 @@ struct thread_info { 
	.cpu        = 0,			\

	.preempt_count  = INIT_PREEMPT_COUNT,	\

	.addr_limit = KERNEL_DS,		\

	.restart_block  = {			\

		.fn = do_no_restart_syscall,	\

	},					\

}



#define init_thread_info    (init_thread_union.thread_info)

arch/arc/kernel/signal.c

+1 −1
Original line number Diff line number Diff line
@@ -104,7 +104,7 @@ SYSCALL_DEFINE0(rt_sigreturn) 
	struct pt_regs *regs = current_pt_regs();



	/* Always make any pending restarted system calls return -EINTR */

	current_thread_info()->restart_block.fn = do_no_restart_syscall;

	current->restart_block.fn = do_no_restart_syscall;



	/* Since we stacked the signal on a word boundary,

	 * then 'sp' should be word aligned here.  If it's

arch/arm/include/asm/thread_info.h

+0 −4
Original line number Diff line number Diff line
@@ -68,7 +68,6 @@ struct thread_info { 
#ifdef CONFIG_ARM_THUMBEE

	unsigned long		thumbee_state;	/* ThumbEE Handler Base register */

#endif

	struct restart_block	restart_block;

};



#define INIT_THREAD_INFO(tsk)						\
@@ -81,9 +80,6 @@ struct thread_info { 
	.cpu_domain	= domain_val(DOMAIN_USER, DOMAIN_MANAGER) |	\

			  domain_val(DOMAIN_KERNEL, DOMAIN_MANAGER) |	\

			  domain_val(DOMAIN_IO, DOMAIN_CLIENT),		\

	.restart_block	= {						\

		.fn	= do_no_restart_syscall,			\

	},								\

}



#define init_thread_info	(init_thread_union.thread_info)