From: Julien Thierry julien.thierry@arm.com
Commit afaf6838f4bc896a711180b702b388b8cfa638fc upstream.
Introduce C and asm helpers to sanitize user address, taking the address range they target into account.
Use asm helper for existing sanitization in __copy_from_user().
Signed-off-by: Julien Thierry julien.thierry@arm.com Signed-off-by: Russell King rmk+kernel@armlinux.org.uk Signed-off-by: David A. Long dave.long@linaro.org Reviewed-by: Julien Thierry julien.thierry@arm.com Signed-off-by: Sasha Levin sashal@kernel.org Signed-off-by: Ard Biesheuvel ardb@kernel.org Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- arch/arm/include/asm/assembler.h | 11 +++++++++++ arch/arm/include/asm/uaccess.h | 26 ++++++++++++++++++++++++++ arch/arm/lib/copy_from_user.S | 6 +----- 3 files changed, 38 insertions(+), 5 deletions(-)
--- a/arch/arm/include/asm/assembler.h +++ b/arch/arm/include/asm/assembler.h @@ -461,6 +461,17 @@ THUMB( orr \reg , \reg , #PSR_T_BIT ) #endif .endm
+ .macro uaccess_mask_range_ptr, addr:req, size:req, limit:req, tmp:req +#ifdef CONFIG_CPU_SPECTRE + sub \tmp, \limit, #1 + subs \tmp, \tmp, \addr @ tmp = limit - 1 - addr + addhs \tmp, \tmp, #1 @ if (tmp >= 0) { + subhss \tmp, \tmp, \size @ tmp = limit - (addr + size) } + movlo \addr, #0 @ if (tmp < 0) addr = NULL + csdb +#endif + .endm + .macro uaccess_disable, tmp, isb=1 #ifdef CONFIG_CPU_SW_DOMAIN_PAN /* --- a/arch/arm/include/asm/uaccess.h +++ b/arch/arm/include/asm/uaccess.h @@ -138,6 +138,32 @@ static inline void set_fs(mm_segment_t f __typeof__(__builtin_choose_expr(sizeof(x) > sizeof(0UL), 0ULL, 0UL))
/* + * Sanitise a uaccess pointer such that it becomes NULL if addr+size + * is above the current addr_limit. + */ +#define uaccess_mask_range_ptr(ptr, size) \ + ((__typeof__(ptr))__uaccess_mask_range_ptr(ptr, size)) +static inline void __user *__uaccess_mask_range_ptr(const void __user *ptr, + size_t size) +{ + void __user *safe_ptr = (void __user *)ptr; + unsigned long tmp; + + asm volatile( + " sub %1, %3, #1\n" + " subs %1, %1, %0\n" + " addhs %1, %1, #1\n" + " subhss %1, %1, %2\n" + " movlo %0, #0\n" + : "+r" (safe_ptr), "=&r" (tmp) + : "r" (size), "r" (current_thread_info()->addr_limit) + : "cc"); + + csdb(); + return safe_ptr; +} + +/* * Single-value transfer routines. They automatically use the right * size if we just have the right pointer type. Note that the functions * which read from user space (*get_*) need to take care not to leak --- a/arch/arm/lib/copy_from_user.S +++ b/arch/arm/lib/copy_from_user.S @@ -93,11 +93,7 @@ ENTRY(arm_copy_from_user) #ifdef CONFIG_CPU_SPECTRE get_thread_info r3 ldr r3, [r3, #TI_ADDR_LIMIT] - adds ip, r1, r2 @ ip=addr+size - sub r3, r3, #1 @ addr_limit - 1 - cmpcc ip, r3 @ if (addr+size > addr_limit - 1) - movcs r1, #0 @ addr = NULL - csdb + uaccess_mask_range_ptr r1, r2, r3, ip #endif
#include "copy_template.S"