Commit 169f9102 authored by Kees Cook's avatar Kees Cook Committed by Russell King (Oracle)
Browse files

ARM: 9350/1: fault: Implement copy_from_kernel_nofault_allowed() 

Under PAN emulation when dumping backtraces from things like the
LKDTM EXEC_USERSPACE test[1], a double fault (which would hang a CPU)
would happen because of dump_instr() attempting to read a userspace
address. Make sure copy_from_kernel_nofault() does not attempt this
any more.

Closes: https://lava.sirena.org.uk/scheduler/job/497571
Link: https://lore.kernel.org/all/202401181125.D48DCB4C@keescook/

 [1]

Reported-by: default avatarMark Brown <broonie@kernel.org>
Suggested-by: default avatarRussell King (Oracle) <rmk+kernel@armlinux.org.uk>
Reviewed-by: default avatarArd Biesheuvel <ardb@kernel.org>
Tested-by: default avatarMark Brown <broonie@kernel.org>
Cc: Wang Kefeng <wangkefeng.wang@huawei.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Ben Hutchings <ben@decadent.org.uk>
Cc: linux-arm-kernel@lists.infradead.org
Signed-off-by: default avatarKees Cook <keescook@chromium.org>
Signed-off-by: default avatarRussell King (Oracle) <rmk+kernel@armlinux.org.uk>
parent daa55957

arch/arm/mm/fault.c

+7 −0
Original line number Diff line number Diff line
@@ -25,6 +25,13 @@ 


#include "fault.h"



bool copy_from_kernel_nofault_allowed(const void *unsafe_src, size_t size)

{

	unsigned long addr = (unsigned long)unsafe_src;



	return addr >= TASK_SIZE && ULONG_MAX - addr >= size;

}



#ifdef CONFIG_MMU



/*