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author | Dan Williams <dan.j.williams@intel.com> | 2018-01-29 17:02:49 -0800 |
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committer | Thomas Gleixner <tglx@linutronix.de> | 2018-01-30 21:54:31 +0100 |
commit | 304ec1b050310548db33063e567123fae8fd0301 (patch) | |
tree | 453a5094b3bdcf3a9cb331850d93d112a04f7d5f /arch/x86/include/asm/uaccess_32.h | |
parent | b5c4ae4f35325d520b230bab6eb3310613b72ac1 (diff) | |
download | linux-stable-304ec1b050310548db33063e567123fae8fd0301.tar.gz linux-stable-304ec1b050310548db33063e567123fae8fd0301.tar.bz2 linux-stable-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_32.h')
-rw-r--r-- | arch/x86/include/asm/uaccess_32.h | 6 |
1 files changed, 3 insertions, 3 deletions
diff --git a/arch/x86/include/asm/uaccess_32.h b/arch/x86/include/asm/uaccess_32.h index 72950401b223..ba2dc1930630 100644 --- a/arch/x86/include/asm/uaccess_32.h +++ b/arch/x86/include/asm/uaccess_32.h @@ -29,21 +29,21 @@ raw_copy_from_user(void *to, const void __user *from, unsigned long n) switch (n) { case 1: ret = 0; - __uaccess_begin(); + __uaccess_begin_nospec(); __get_user_asm_nozero(*(u8 *)to, from, ret, "b", "b", "=q", 1); __uaccess_end(); return ret; case 2: ret = 0; - __uaccess_begin(); + __uaccess_begin_nospec(); __get_user_asm_nozero(*(u16 *)to, from, ret, "w", "w", "=r", 2); __uaccess_end(); return ret; case 4: ret = 0; - __uaccess_begin(); + __uaccess_begin_nospec(); __get_user_asm_nozero(*(u32 *)to, from, ret, "l", "k", "=r", 4); __uaccess_end(); |