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| author | Julien Thierry <julien.thierry@arm.com> | 2018-09-11 11:14:50 +0200 |
|---|---|---|
| committer | Russell King <rmk+kernel@armlinux.org.uk> | 2018-10-05 11:51:15 +0200 |
| commit | afaf6838f4bc896a711180b702b388b8cfa638fc (patch) | |
| tree | 1971dfe3cd88aba8e98339d928f17a9dd87cf285 | |
| parent | ARM: 8795/1: spectre-v1.1: use put_user() for __put_user() (diff) | |
| download | linux-afaf6838f4bc896a711180b702b388b8cfa638fc.tar.xz linux-afaf6838f4bc896a711180b702b388b8cfa638fc.zip | |
ARM: 8796/1: spectre-v1,v1.1: provide helpers for address sanitization
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>
| -rw-r--r-- | arch/arm/include/asm/assembler.h | 11 | ||||
| -rw-r--r-- | arch/arm/include/asm/uaccess.h | 26 | ||||
| -rw-r--r-- | arch/arm/lib/copy_from_user.S | 6 |
3 files changed, 38 insertions, 5 deletions
diff --git a/arch/arm/include/asm/assembler.h b/arch/arm/include/asm/assembler.h index f0515f60cff5..39651c1ec157 100644 --- a/arch/arm/include/asm/assembler.h +++ b/arch/arm/include/asm/assembler.h @@ -467,6 +467,17 @@ 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 /* diff --git a/arch/arm/include/asm/uaccess.h b/arch/arm/include/asm/uaccess.h index cf50b030c62c..a5807b67ca8a 100644 --- a/arch/arm/include/asm/uaccess.h +++ b/arch/arm/include/asm/uaccess.h @@ -100,6 +100,32 @@ static inline void set_fs(mm_segment_t fs) __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 diff --git a/arch/arm/lib/copy_from_user.S b/arch/arm/lib/copy_from_user.S index a826df3d3814..6709a8d33963 100644 --- 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" |