From f56141e3e2d9aabf7e6b89680ab572c2cdbb2a24 Mon Sep 17 00:00:00 2001 From: Andy Lutomirski Date: Thu, 12 Feb 2015 15:01:14 -0800 Subject: 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: Andy Lutomirski Cc: Thomas Gleixner Cc: Al Viro Cc: "H. Peter Anvin" Cc: Ingo Molnar Cc: Kees Cook Cc: David Miller Acked-by: Richard Weinberger Cc: Richard Henderson Cc: Ivan Kokshaysky Cc: Matt Turner Cc: Vineet Gupta Cc: Russell King Cc: Catalin Marinas Cc: Will Deacon Cc: Haavard Skinnemoen Cc: Hans-Christian Egtvedt Cc: Steven Miao Cc: Mark Salter Cc: Aurelien Jacquiot Cc: Mikael Starvik Cc: Jesper Nilsson Cc: David Howells Cc: Richard Kuo Cc: "Luck, Tony" Cc: Geert Uytterhoeven Cc: Michal Simek Cc: Ralf Baechle Cc: Jonas Bonn Cc: "James E.J. Bottomley" Cc: Helge Deller Cc: Benjamin Herrenschmidt Cc: Paul Mackerras Acked-by: Michael Ellerman (powerpc) Tested-by: Michael Ellerman (powerpc) Cc: Martin Schwidefsky Cc: Heiko Carstens Cc: Chen Liqin Cc: Lennox Wu Cc: Chris Metcalf Cc: Guan Xuetao Cc: Chris Zankel Cc: Max Filippov Cc: Oleg Nesterov Cc: Guenter Roeck Signed-off-by: James Hogan Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- arch/frv/include/asm/thread_info.h | 4 ---- arch/frv/kernel/asm-offsets.c | 1 - arch/frv/kernel/signal.c | 2 +- 3 files changed, 1 insertion(+), 6 deletions(-) (limited to 'arch/frv') diff --git a/arch/frv/include/asm/thread_info.h b/arch/frv/include/asm/thread_info.h index af29e17c0181..6b917f1c2955 100644 --- a/arch/frv/include/asm/thread_info.h +++ b/arch/frv/include/asm/thread_info.h @@ -41,7 +41,6 @@ struct thread_info { * 0-0xBFFFFFFF for user-thead * 0-0xFFFFFFFF for kernel-thread */ - struct restart_block restart_block; __u8 supervisor_stack[0]; }; @@ -65,9 +64,6 @@ 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) diff --git a/arch/frv/kernel/asm-offsets.c b/arch/frv/kernel/asm-offsets.c index 9de96843a278..446e89d500cc 100644 --- a/arch/frv/kernel/asm-offsets.c +++ b/arch/frv/kernel/asm-offsets.c @@ -40,7 +40,6 @@ void foo(void) OFFSET(TI_CPU, thread_info, cpu); OFFSET(TI_PREEMPT_COUNT, thread_info, preempt_count); OFFSET(TI_ADDR_LIMIT, thread_info, addr_limit); - OFFSET(TI_RESTART_BLOCK, thread_info, restart_block); BLANK(); /* offsets into register file storage */ diff --git a/arch/frv/kernel/signal.c b/arch/frv/kernel/signal.c index dc3d59de0870..336713ab4745 100644 --- a/arch/frv/kernel/signal.c +++ b/arch/frv/kernel/signal.c @@ -62,7 +62,7 @@ static int restore_sigcontext(struct sigcontext __user *sc, int *_gr8) unsigned long tbr, psr; /* 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; tbr = user->i.tbr; psr = user->i.psr; -- cgit v1.2.3