diff options
| author | Dan Williams <dan.j.williams@intel.com> | 2018-01-30 02:02:49 +0100 |
|---|---|---|
| committer | Thomas Gleixner <tglx@linutronix.de> | 2018-01-30 21:54:31 +0100 |
| commit | 304ec1b050310548db33063e567123fae8fd0301 (patch) | |
| tree | 453a5094b3bdcf3a9cb331850d93d112a04f7d5f /arch/x86/include/asm/uaccess.h | |
| parent | x86/usercopy: Replace open coded stac/clac with __uaccess_{begin, end} (diff) | |
| download | linux-304ec1b050310548db33063e567123fae8fd0301.tar.xz linux-304ec1b050310548db33063e567123fae8fd0301.zip | |
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
Diffstat (limited to 'arch/x86/include/asm/uaccess.h')
| -rw-r--r-- | arch/x86/include/asm/uaccess.h | 6 |
1 files changed, 3 insertions, 3 deletions
diff --git a/arch/x86/include/asm/uaccess.h b/arch/x86/include/asm/uaccess.h index 663e9bde9fc9..aae77eb8491c 100644 --- a/arch/x86/include/asm/uaccess.h +++ b/arch/x86/include/asm/uaccess.h @@ -450,7 +450,7 @@ 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; \ @@ -557,7 +557,7 @@ 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 { \ @@ -591,7 +591,7 @@ 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: \ { \ |