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/avr32/include/asm/thread_info.h | 4 ---- arch/avr32/kernel/asm-offsets.c | 1 - arch/avr32/kernel/signal.c | 2 +- 3 files changed, 1 insertion(+), 6 deletions(-) (limited to 'arch/avr32') diff --git a/arch/avr32/include/asm/thread_info.h b/arch/avr32/include/asm/thread_info.h index a978f3f..d56afa9 100644 --- a/arch/avr32/include/asm/thread_info.h +++ b/arch/avr32/include/asm/thread_info.h @@ -30,7 +30,6 @@ struct thread_info { saved by debug handler when setting up trampoline */ - struct restart_block restart_block; __u8 supervisor_stack[0]; }; @@ -41,9 +40,6 @@ struct thread_info { .flags = 0, \ .cpu = 0, \ .preempt_count = INIT_PREEMPT_COUNT, \ - .restart_block = { \ - .fn = do_no_restart_syscall \ - } \ } #define init_thread_info (init_thread_union.thread_info) diff --git a/arch/avr32/kernel/asm-offsets.c b/arch/avr32/kernel/asm-offsets.c index d6a8193..e41c845 100644 --- a/arch/avr32/kernel/asm-offsets.c +++ b/arch/avr32/kernel/asm-offsets.c @@ -18,7 +18,6 @@ void foo(void) OFFSET(TI_preempt_count, thread_info, preempt_count); OFFSET(TI_rar_saved, thread_info, rar_saved); OFFSET(TI_rsr_saved, thread_info, rsr_saved); - OFFSET(TI_restart_block, thread_info, restart_block); BLANK(); OFFSET(TSK_active_mm, task_struct, active_mm); BLANK(); diff --git a/arch/avr32/kernel/signal.c b/arch/avr32/kernel/signal.c index d309fbc..8f1c63b 100644 --- a/arch/avr32/kernel/signal.c +++ b/arch/avr32/kernel/signal.c @@ -69,7 +69,7 @@ asmlinkage int sys_rt_sigreturn(struct pt_regs *regs) sigset_t set; /* 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; frame = (struct rt_sigframe __user *)regs->sp; pr_debug("SIG return: frame = %p\n", frame); -- cgit v1.1