| From foo@baz Thu Feb 8 03:32:24 CET 2018 |
| From: Dan Williams <dan.j.williams@intel.com> |
| Date: Mon, 29 Jan 2018 17:02:49 -0800 |
| Subject: x86/uaccess: Use __uaccess_begin_nospec() and uaccess_try_nospec |
| |
| From: Dan Williams <dan.j.williams@intel.com> |
| |
| |
| (cherry picked from commit 304ec1b050310548db33063e567123fae8fd0301) |
| |
| 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 |
| Signed-off-by: David Woodhouse <dwmw@amazon.co.uk> |
| Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> |
| --- |
| arch/x86/include/asm/uaccess.h | 6 +++--- |
| arch/x86/include/asm/uaccess_32.h | 12 ++++++------ |
| arch/x86/include/asm/uaccess_64.h | 12 ++++++------ |
| arch/x86/lib/usercopy_32.c | 4 ++-- |
| 4 files changed, 17 insertions(+), 17 deletions(-) |
| |
| --- a/arch/x86/include/asm/uaccess.h |
| +++ b/arch/x86/include/asm/uaccess.h |
| @@ -437,7 +437,7 @@ do { \ |
| ({ \ |
| int __gu_err; \ |
| __inttype(*(ptr)) __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; \ |
| @@ -547,7 +547,7 @@ struct __large_struct { unsigned long bu |
| * 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 { \ |
| @@ -582,7 +582,7 @@ 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: \ |
| { \ |
| --- a/arch/x86/include/asm/uaccess_32.h |
| +++ b/arch/x86/include/asm/uaccess_32.h |
| @@ -102,17 +102,17 @@ __copy_from_user(void *to, const void __ |
| |
| 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; |
| @@ -130,17 +130,17 @@ static __always_inline unsigned long __c |
| |
| 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; |
| --- a/arch/x86/include/asm/uaccess_64.h |
| +++ b/arch/x86/include/asm/uaccess_64.h |
| @@ -59,31 +59,31 @@ int __copy_from_user_nocheck(void *dst, |
| 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)) |
| @@ -93,7 +93,7 @@ int __copy_from_user_nocheck(void *dst, |
| __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)) |
| --- a/arch/x86/lib/usercopy_32.c |
| +++ b/arch/x86/lib/usercopy_32.c |
| @@ -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 |
| @@ -627,7 +627,7 @@ EXPORT_SYMBOL(__copy_from_user_ll_nocach |
| 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 && static_cpu_has(X86_FEATURE_XMM2)) |
| n = __copy_user_intel_nocache(to, from, n); |