diff options
Diffstat (limited to 'common/recipes-kernel/linux/linux-yocto-4.9.21/0031-x86-get_user-Use-pointer-masking-to-limit-speculatio.patch')
| -rw-r--r-- | common/recipes-kernel/linux/linux-yocto-4.9.21/0031-x86-get_user-Use-pointer-masking-to-limit-speculatio.patch | 100 |
1 files changed, 100 insertions, 0 deletions
diff --git a/common/recipes-kernel/linux/linux-yocto-4.9.21/0031-x86-get_user-Use-pointer-masking-to-limit-speculatio.patch b/common/recipes-kernel/linux/linux-yocto-4.9.21/0031-x86-get_user-Use-pointer-masking-to-limit-speculatio.patch new file mode 100644 index 00000000..c58bff80 --- /dev/null +++ b/common/recipes-kernel/linux/linux-yocto-4.9.21/0031-x86-get_user-Use-pointer-masking-to-limit-speculatio.patch @@ -0,0 +1,100 @@ +From aa9e88541e4443ffd498e0dd1912b2e658a659e6 Mon Sep 17 00:00:00 2001 +From: Dan Williams <dan.j.williams@intel.com> +Date: Mon, 29 Jan 2018 17:02:54 -0800 +Subject: [PATCH 31/42] x86/get_user: Use pointer masking to limit speculation + +(cherry picked from commit c7f631cb07e7da06ac1d231ca178452339e32a94) + +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. + +Unlike the __get_user() case get_user() includes the address limit check +near the pointer de-reference. With that locality the speculation can be +mitigated with pointer narrowing rather than a barrier, i.e. +array_index_nospec(). Where the narrowing is performed by: + + cmp %limit, %ptr + sbb %mask, %mask + and %mask, %ptr + +With respect to speculation the value of %ptr is either less than %limit +or NULL. + +Co-developed-by: Linus Torvalds <torvalds@linux-foundation.org> +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: Andy Lutomirski <luto@kernel.org> +Cc: torvalds@linux-foundation.org +Cc: alan@linux.intel.com +Link: https://lkml.kernel.org/r/151727417469.33451.11804043010080838495.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/lib/getuser.S | 10 ++++++++++ + 1 file changed, 10 insertions(+) + +diff --git a/arch/x86/lib/getuser.S b/arch/x86/lib/getuser.S +index 37b62d4..b12b214 100644 +--- a/arch/x86/lib/getuser.S ++++ b/arch/x86/lib/getuser.S +@@ -39,6 +39,8 @@ ENTRY(__get_user_1) + mov PER_CPU_VAR(current_task), %_ASM_DX + cmp TASK_addr_limit(%_ASM_DX),%_ASM_AX + jae bad_get_user ++ sbb %_ASM_DX, %_ASM_DX /* array_index_mask_nospec() */ ++ and %_ASM_DX, %_ASM_AX + ASM_STAC + 1: movzbl (%_ASM_AX),%edx + xor %eax,%eax +@@ -53,6 +55,8 @@ ENTRY(__get_user_2) + mov PER_CPU_VAR(current_task), %_ASM_DX + cmp TASK_addr_limit(%_ASM_DX),%_ASM_AX + jae bad_get_user ++ sbb %_ASM_DX, %_ASM_DX /* array_index_mask_nospec() */ ++ and %_ASM_DX, %_ASM_AX + ASM_STAC + 2: movzwl -1(%_ASM_AX),%edx + xor %eax,%eax +@@ -67,6 +71,8 @@ ENTRY(__get_user_4) + mov PER_CPU_VAR(current_task), %_ASM_DX + cmp TASK_addr_limit(%_ASM_DX),%_ASM_AX + jae bad_get_user ++ sbb %_ASM_DX, %_ASM_DX /* array_index_mask_nospec() */ ++ and %_ASM_DX, %_ASM_AX + ASM_STAC + 3: movl -3(%_ASM_AX),%edx + xor %eax,%eax +@@ -82,6 +88,8 @@ ENTRY(__get_user_8) + mov PER_CPU_VAR(current_task), %_ASM_DX + cmp TASK_addr_limit(%_ASM_DX),%_ASM_AX + jae bad_get_user ++ sbb %_ASM_DX, %_ASM_DX /* array_index_mask_nospec() */ ++ and %_ASM_DX, %_ASM_AX + ASM_STAC + 4: movq -7(%_ASM_AX),%rdx + xor %eax,%eax +@@ -93,6 +101,8 @@ ENTRY(__get_user_8) + mov PER_CPU_VAR(current_task), %_ASM_DX + cmp TASK_addr_limit(%_ASM_DX),%_ASM_AX + jae bad_get_user_8 ++ sbb %_ASM_DX, %_ASM_DX /* array_index_mask_nospec() */ ++ and %_ASM_DX, %_ASM_AX + ASM_STAC + 4: movl -7(%_ASM_AX),%edx + 5: movl -3(%_ASM_AX),%ecx +-- +2.7.4 + |