4.4-stable review patch. If anyone has any objections, please let me know.
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From: Dan Williams dan.j.williams@intel.com
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@dwil... [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 --- arch/x86/include/asm/uaccess.h | 6 +++--- arch/x86/include/asm/uaccess_32.h | 26 +++++++++++++------------- arch/x86/include/asm/uaccess_64.h | 20 ++++++++++---------- arch/x86/lib/usercopy_32.c | 10 +++++----- 4 files changed, 31 insertions(+), 31 deletions(-)
--- a/arch/x86/include/asm/uaccess.h +++ b/arch/x86/include/asm/uaccess.h @@ -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 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 { \ @@ -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: \ { \ --- a/arch/x86/include/asm/uaccess_32.h +++ b/arch/x86/include/asm/uaccess_32.h @@ -48,25 +48,25 @@ __copy_to_user_inatomic(void __user *to,
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, cons
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 __
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 __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 @@ -57,31 +57,31 @@ 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)) @@ -91,7 +91,7 @@ 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)) @@ -190,7 +190,7 @@ int __copy_in_user(void __user *dst, con 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, con } 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, con
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, con } case 8: { u64 tmp; - __uaccess_begin(); + __uaccess_begin_nospec(); __get_user_asm(tmp, (u64 __user *)src, ret, "q", "", "=r", 8); 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 @@ -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_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 && cpu_has_xmm2) n = __copy_user_intel_nocache(to, from, n);