mirror of https://gitee.com/openkylin/linux.git
x86/uaccess: Use __uaccess_begin_nospec() and uaccess_try_nospec
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
This commit is contained in:
Dan Williams
Thomas Gleixner
parent
b5c4ae4f35
commit
304ec1b050
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@ -450,7 +450,7 @@ do { \
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({ \
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int __gu_err; \
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__inttype(*(ptr)) __gu_val; \
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__uaccess_begin(); \
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__uaccess_begin_nospec(); \
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__get_user_size(__gu_val, (ptr), (size), __gu_err, -EFAULT); \
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__uaccess_end(); \
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(x) = (__force __typeof__(*(ptr)))__gu_val; \
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@ -557,7 +557,7 @@ struct __large_struct { unsigned long buf[100]; };
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* get_user_ex(...);
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* } get_user_catch(err)
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*/
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#define get_user_try uaccess_try
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#define get_user_try uaccess_try_nospec
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#define get_user_catch(err) uaccess_catch(err)
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#define get_user_ex(x, ptr) do { \
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@ -591,7 +591,7 @@ extern void __cmpxchg_wrong_size(void)
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__typeof__(ptr) __uval = (uval); \
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__typeof__(*(ptr)) __old = (old); \
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__typeof__(*(ptr)) __new = (new); \
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__uaccess_begin(); \
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__uaccess_begin_nospec(); \
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switch (size) { \
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case 1: \
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{ \
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@ -29,21 +29,21 @@ raw_copy_from_user(void *to, const void __user *from, unsigned long n)
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switch (n) {
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case 1:
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ret = 0;
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__uaccess_begin();
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__uaccess_begin_nospec();
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__get_user_asm_nozero(*(u8 *)to, from, ret,
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"b", "b", "=q", 1);
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__uaccess_end();
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return ret;
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case 2:
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ret = 0;
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__uaccess_begin();
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__uaccess_begin_nospec();
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__get_user_asm_nozero(*(u16 *)to, from, ret,
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"w", "w", "=r", 2);
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__uaccess_end();
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return ret;
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case 4:
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ret = 0;
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__uaccess_begin();
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__uaccess_begin_nospec();
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__get_user_asm_nozero(*(u32 *)to, from, ret,
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"l", "k", "=r", 4);
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__uaccess_end();
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@ -55,31 +55,31 @@ raw_copy_from_user(void *dst, const void __user *src, unsigned long size)
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return copy_user_generic(dst, (__force void *)src, size);
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switch (size) {
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case 1:
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__uaccess_begin();
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__uaccess_begin_nospec();
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__get_user_asm_nozero(*(u8 *)dst, (u8 __user *)src,
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ret, "b", "b", "=q", 1);
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__uaccess_end();
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return ret;
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case 2:
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__uaccess_begin();
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__uaccess_begin_nospec();
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__get_user_asm_nozero(*(u16 *)dst, (u16 __user *)src,
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ret, "w", "w", "=r", 2);
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__uaccess_end();
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return ret;
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case 4:
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__uaccess_begin();
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__uaccess_begin_nospec();
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__get_user_asm_nozero(*(u32 *)dst, (u32 __user *)src,
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ret, "l", "k", "=r", 4);
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__uaccess_end();
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return ret;
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case 8:
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__uaccess_begin();
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__uaccess_begin_nospec();
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__get_user_asm_nozero(*(u64 *)dst, (u64 __user *)src,
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ret, "q", "", "=r", 8);
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__uaccess_end();
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return ret;
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case 10:
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__uaccess_begin();
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__uaccess_begin_nospec();
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__get_user_asm_nozero(*(u64 *)dst, (u64 __user *)src,
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ret, "q", "", "=r", 10);
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if (likely(!ret))
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@ -89,7 +89,7 @@ raw_copy_from_user(void *dst, const void __user *src, unsigned long size)
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__uaccess_end();
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return ret;
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case 16:
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__uaccess_begin();
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__uaccess_begin_nospec();
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__get_user_asm_nozero(*(u64 *)dst, (u64 __user *)src,
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ret, "q", "", "=r", 16);
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if (likely(!ret))
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@ -331,7 +331,7 @@ do { \
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unsigned long __copy_user_ll(void *to, const void *from, unsigned long n)
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{
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__uaccess_begin();
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__uaccess_begin_nospec();
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if (movsl_is_ok(to, from, n))
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__copy_user(to, from, n);
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else
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@ -344,7 +344,7 @@ EXPORT_SYMBOL(__copy_user_ll);
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unsigned long __copy_from_user_ll_nocache_nozero(void *to, const void __user *from,
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unsigned long n)
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{
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__uaccess_begin();
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__uaccess_begin_nospec();
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#ifdef CONFIG_X86_INTEL_USERCOPY
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if (n > 64 && static_cpu_has(X86_FEATURE_XMM2))
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n = __copy_user_intel_nocache(to, from, n);
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