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x86/uaccess: Use __uaccess_begin_nospec() and uaccess_try_nospec

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commit 304ec1b050310548db33063e567123fae8fd0301 upstream.

Quoting Linus:

    I do think that it would be a good idea to very expressly document
    the fact that it's not that the user access itself is unsafe. I do
    agree that things like "get_user()" want to be protected, but not
    because of any direct bugs or problems with get_user() and friends,
    but simply because get_user() is an excellent source of a pointer
    that is obviously controlled from a potentially attacking user
    space. So it's a prime candidate for then finding _subsequent_
    accesses that can then be used to perturb the cache.

__uaccess_begin_nospec() covers __get_user() and copy_from_iter() where the
limit check is far away from the user pointer de-reference. In those cases
a barrier_nospec() prevents speculation with a potential pointer to
privileged memory. uaccess_try_nospec covers get_user_try.

Suggested-by: Linus Torvalds <torvalds@linux-foundation.org>
Suggested-by: Andi Kleen <ak@linux.intel.com>
Signed-off-by: Dan Williams <dan.j.williams@intel.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: linux-arch@vger.kernel.org
Cc: Kees Cook <keescook@chromium.org>
Cc: kernel-hardening@lists.openwall.com
Cc: gregkh@linuxfoundation.org
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: alan@linux.intel.com
Link: https://lkml.kernel.org/r/151727416953.33451.10508284228526170604.stgit@dwillia2-desk3.amr.corp.intel.com
[bwh: Backported to 4.4:
 - Convert several more functions to use __uaccess_begin_nospec(), that
   are just wrappers in mainline
 - Adjust context]
Signed-off-by: Ben Hutchings <ben.hutchings@codethink.co.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Dan Williams 2018-01-29 17:02:49 -08:00 • committed by Greg Kroah-Hartman
parent 557cd0d20e
commit 67e326e034
4 changed files with 31 additions and 31 deletions
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6
arch/x86/include/asm/uaccess.h
View file

@ -436,7 +436,7 @@ do { \
({ \
int __gu_err; \
unsigned long __gu_val; \
__uaccess_begin(); \
__uaccess_begin_nospec(); \
__get_user_size(__gu_val, (ptr), (size), __gu_err, -EFAULT); \
__uaccess_end(); \
(x) = (__force __typeof__(*(ptr)))__gu_val; \
@ -546,7 +546,7 @@ struct __large_struct { unsigned long buf[100]; };
* get_user_ex(...);
* } get_user_catch(err)
*/
#define get_user_try uaccess_try
#define get_user_try uaccess_try_nospec
#define get_user_catch(err) uaccess_catch(err)
#define get_user_ex(x, ptr) do { \
@ -581,7 +581,7 @@ extern void __cmpxchg_wrong_size(void)
__typeof__(ptr) __uval = (uval); \
__typeof__(*(ptr)) __old = (old); \
__typeof__(*(ptr)) __new = (new); \
__uaccess_begin(); \
__uaccess_begin_nospec(); \
switch (size) { \
case 1: \
{ \

26
arch/x86/include/asm/uaccess_32.h
View file

@ -48,25 +48,25 @@ __copy_to_user_inatomic(void __user *to, const void *from, unsigned long n)
switch (n) {
case 1:
__uaccess_begin();
__uaccess_begin_nospec();
__put_user_size(*(u8 *)from, (u8 __user *)to,
1, ret, 1);
__uaccess_end();
return ret;
case 2:
__uaccess_begin();
__uaccess_begin_nospec();
__put_user_size(*(u16 *)from, (u16 __user *)to,
2, ret, 2);
__uaccess_end();
return ret;
case 4:
__uaccess_begin();
__uaccess_begin_nospec();
__put_user_size(*(u32 *)from, (u32 __user *)to,
4, ret, 4);
__uaccess_end();
return ret;
case 8:
__uaccess_begin();
__uaccess_begin_nospec();
__put_user_size(*(u64 *)from, (u64 __user *)to,
8, ret, 8);
__uaccess_end();
@ -111,17 +111,17 @@ __copy_from_user_inatomic(void *to, const void __user *from, unsigned long n)
switch (n) {
case 1:
__uaccess_begin();
__uaccess_begin_nospec();
__get_user_size(*(u8 *)to, from, 1, ret, 1);
__uaccess_end();
return ret;
case 2:
__uaccess_begin();
__uaccess_begin_nospec();
__get_user_size(*(u16 *)to, from, 2, ret, 2);
__uaccess_end();
return ret;
case 4:
__uaccess_begin();
__uaccess_begin_nospec();
__get_user_size(*(u32 *)to, from, 4, ret, 4);
__uaccess_end();
return ret;
@ -162,17 +162,17 @@ __copy_from_user(void *to, const void __user *from, unsigned long n)
switch (n) {
case 1:
__uaccess_begin();
__uaccess_begin_nospec();
__get_user_size(*(u8 *)to, from, 1, ret, 1);
__uaccess_end();
return ret;
case 2:
__uaccess_begin();
__uaccess_begin_nospec();
__get_user_size(*(u16 *)to, from, 2, ret, 2);
__uaccess_end();
return ret;
case 4:
__uaccess_begin();
__uaccess_begin_nospec();
__get_user_size(*(u32 *)to, from, 4, ret, 4);
__uaccess_end();
return ret;
@ -190,17 +190,17 @@ static __always_inline unsigned long __copy_from_user_nocache(void *to,
switch (n) {
case 1:
__uaccess_begin();
__uaccess_begin_nospec();
__get_user_size(*(u8 *)to, from, 1, ret, 1);
__uaccess_end();
return ret;
case 2:
__uaccess_begin();
__uaccess_begin_nospec();
__get_user_size(*(u16 *)to, from, 2, ret, 2);
__uaccess_end();
return ret;
case 4:
__uaccess_begin();
__uaccess_begin_nospec();
__get_user_size(*(u32 *)to, from, 4, ret, 4);
__uaccess_end();
return ret;

20
arch/x86/include/asm/uaccess_64.h
View file

@ -57,31 +57,31 @@ int __copy_from_user_nocheck(void *dst, const void __user *src, unsigned size)
return copy_user_generic(dst, (__force void *)src, size);
switch (size) {
case 1:
__uaccess_begin();
__uaccess_begin_nospec();
__get_user_asm(*(u8 *)dst, (u8 __user *)src,
ret, "b", "b", "=q", 1);
__uaccess_end();
return ret;
case 2:
__uaccess_begin();
__uaccess_begin_nospec();
__get_user_asm(*(u16 *)dst, (u16 __user *)src,
ret, "w", "w", "=r", 2);
__uaccess_end();
return ret;
case 4:
__uaccess_begin();
__uaccess_begin_nospec();
__get_user_asm(*(u32 *)dst, (u32 __user *)src,
ret, "l", "k", "=r", 4);
__uaccess_end();
return ret;
case 8:
__uaccess_begin();
__uaccess_begin_nospec();
__get_user_asm(*(u64 *)dst, (u64 __user *)src,
ret, "q", "", "=r", 8);
__uaccess_end();
return ret;
case 10:
__uaccess_begin();
__uaccess_begin_nospec();
__get_user_asm(*(u64 *)dst, (u64 __user *)src,
ret, "q", "", "=r", 10);
if (likely(!ret))
@ -91,7 +91,7 @@ int __copy_from_user_nocheck(void *dst, const void __user *src, unsigned size)
__uaccess_end();
return ret;
case 16:
__uaccess_begin();
__uaccess_begin_nospec();
__get_user_asm(*(u64 *)dst, (u64 __user *)src,
ret, "q", "", "=r", 16);
if (likely(!ret))
@ -190,7 +190,7 @@ int __copy_in_user(void __user *dst, const void __user *src, unsigned size)
switch (size) {
case 1: {
u8 tmp;
__uaccess_begin();
__uaccess_begin_nospec();
__get_user_asm(tmp, (u8 __user *)src,
ret, "b", "b", "=q", 1);
if (likely(!ret))
@ -201,7 +201,7 @@ int __copy_in_user(void __user *dst, const void __user *src, unsigned size)
}
case 2: {
u16 tmp;
__uaccess_begin();
__uaccess_begin_nospec();
__get_user_asm(tmp, (u16 __user *)src,
ret, "w", "w", "=r", 2);
if (likely(!ret))
@ -213,7 +213,7 @@ int __copy_in_user(void __user *dst, const void __user *src, unsigned size)
case 4: {
u32 tmp;
__uaccess_begin();
__uaccess_begin_nospec();
__get_user_asm(tmp, (u32 __user *)src,
ret, "l", "k", "=r", 4);
if (likely(!ret))
@ -224,7 +224,7 @@ int __copy_in_user(void __user *dst, const void __user *src, unsigned size)
}
case 8: {
u64 tmp;
__uaccess_begin();
__uaccess_begin_nospec();
__get_user_asm(tmp, (u64 __user *)src,
ret, "q", "", "=r", 8);
if (likely(!ret))

10
arch/x86/lib/usercopy_32.c
View file

@ -570,7 +570,7 @@ do { \
unsigned long __copy_to_user_ll(void __user *to, const void *from,
unsigned long n)
{
__uaccess_begin();
__uaccess_begin_nospec();
if (movsl_is_ok(to, from, n))
__copy_user(to, from, n);
else
@ -583,7 +583,7 @@ EXPORT_SYMBOL(__copy_to_user_ll);
unsigned long __copy_from_user_ll(void *to, const void __user *from,
unsigned long n)
{
__uaccess_begin();
__uaccess_begin_nospec();
if (movsl_is_ok(to, from, n))
__copy_user_zeroing(to, from, n);
else
@ -596,7 +596,7 @@ EXPORT_SYMBOL(__copy_from_user_ll);
unsigned long __copy_from_user_ll_nozero(void *to, const void __user *from,
unsigned long n)
{
__uaccess_begin();
__uaccess_begin_nospec();
if (movsl_is_ok(to, from, n))
__copy_user(to, from, n);
else
@ -610,7 +610,7 @@ EXPORT_SYMBOL(__copy_from_user_ll_nozero);
unsigned long __copy_from_user_ll_nocache(void *to, const void __user *from,
unsigned long n)
{
__uaccess_begin();
__uaccess_begin_nospec();
#ifdef CONFIG_X86_INTEL_USERCOPY
if (n > 64 && cpu_has_xmm2)
n = __copy_user_zeroing_intel_nocache(to, from, n);
@ -627,7 +627,7 @@ EXPORT_SYMBOL(__copy_from_user_ll_nocache);
unsigned long __copy_from_user_ll_nocache_nozero(void *to, const void __user *from,
unsigned long n)
{
__uaccess_begin();
__uaccess_begin_nospec();
#ifdef CONFIG_X86_INTEL_USERCOPY
if (n > 64 && cpu_has_xmm2)
n = __copy_user_intel_nocache(to, from, n);