| From 0a2d7d9b1e63dd28baf6c8e1416b64a33f89c900 Mon Sep 17 00:00:00 2001 |
| From: Linus Torvalds <torvalds@linux-foundation.org> |
| Date: Tue, 23 Feb 2016 14:58:52 -0800 |
| Subject: x86: fix SMAP in 32-bit environments |
| |
| commit de9e478b9d49f3a0214310d921450cf5bb4a21e6 upstream. |
| |
| In commit 11f1a4b9755f ("x86: reorganize SMAP handling in user space |
| accesses") I changed how the stac/clac instructions were generated |
| around the user space accesses, which then made it possible to do |
| batched accesses efficiently for user string copies etc. |
| |
| However, in doing so, I completely spaced out, and didn't even think |
| about the 32-bit case. And nobody really even seemed to notice, because |
| SMAP doesn't even exist until modern Skylake processors, and you'd have |
| to be crazy to run 32-bit kernels on a modern CPU. |
| |
| Which brings us to Andy Lutomirski. |
| |
| He actually tested the 32-bit kernel on new hardware, and noticed that |
| it doesn't work. My bad. The trivial fix is to add the required |
| uaccess begin/end markers around the raw accesses in <asm/uaccess_32.h>. |
| |
| I feel a bit bad about this patch, just because that header file really |
| should be cleaned up to avoid all the duplicated code in it, and this |
| commit just expands on the problem. But this just fixes the bug without |
| any bigger cleanup surgery. |
| |
| Reported-and-tested-by: Andy Lutomirski <luto@kernel.org> |
| Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org> |
| [bwh: Backported to 3.16: There's no 'case 8' in __copy_to_user_inatomic()] |
| Signed-off-by: Ben Hutchings <ben@decadent.org.uk> |
| |
| arch/x86/include/asm/uaccess_32.h | 24 ++++++++++++++++++++++++ |
| 1 file changed, 24 insertions(+) |
| |
| diff --git a/arch/x86/include/asm/uaccess_32.h b/arch/x86/include/asm/uaccess_32.h |
| index 3c03a5de64d3..b25d109fb95a 100644 |
| |
| |
| @@ -48,16 +48,22 @@ __copy_to_user_inatomic(void __user *to, const void *from, unsigned long n) |
| |
| switch (n) { |
| case 1: |
| + __uaccess_begin(); |
| __put_user_size(*(u8 *)from, (u8 __user *)to, |
| 1, ret, 1); |
| + __uaccess_end(); |
| return ret; |
| case 2: |
| + __uaccess_begin(); |
| __put_user_size(*(u16 *)from, (u16 __user *)to, |
| 2, ret, 2); |
| + __uaccess_end(); |
| return ret; |
| case 4: |
| + __uaccess_begin(); |
| __put_user_size(*(u32 *)from, (u32 __user *)to, |
| 4, ret, 4); |
| + __uaccess_end(); |
| return ret; |
| } |
| } |
| @@ -98,13 +104,19 @@ __copy_from_user_inatomic(void *to, const void __user *from, unsigned long n) |
| |
| switch (n) { |
| case 1: |
| + __uaccess_begin(); |
| __get_user_size(*(u8 *)to, from, 1, ret, 1); |
| + __uaccess_end(); |
| return ret; |
| case 2: |
| + __uaccess_begin(); |
| __get_user_size(*(u16 *)to, from, 2, ret, 2); |
| + __uaccess_end(); |
| return ret; |
| case 4: |
| + __uaccess_begin(); |
| __get_user_size(*(u32 *)to, from, 4, ret, 4); |
| + __uaccess_end(); |
| return ret; |
| } |
| } |
| @@ -142,13 +154,19 @@ __copy_from_user(void *to, const void __user *from, unsigned long n) |
| |
| switch (n) { |
| case 1: |
| + __uaccess_begin(); |
| __get_user_size(*(u8 *)to, from, 1, ret, 1); |
| + __uaccess_end(); |
| return ret; |
| case 2: |
| + __uaccess_begin(); |
| __get_user_size(*(u16 *)to, from, 2, ret, 2); |
| + __uaccess_end(); |
| return ret; |
| case 4: |
| + __uaccess_begin(); |
| __get_user_size(*(u32 *)to, from, 4, ret, 4); |
| + __uaccess_end(); |
| return ret; |
| } |
| } |
| @@ -164,13 +182,19 @@ static __always_inline unsigned long __copy_from_user_nocache(void *to, |
| |
| switch (n) { |
| case 1: |
| + __uaccess_begin(); |
| __get_user_size(*(u8 *)to, from, 1, ret, 1); |
| + __uaccess_end(); |
| return ret; |
| case 2: |
| + __uaccess_begin(); |
| __get_user_size(*(u16 *)to, from, 2, ret, 2); |
| + __uaccess_end(); |
| return ret; |
| case 4: |
| + __uaccess_begin(); |
| __get_user_size(*(u32 *)to, from, 4, ret, 4); |
| + __uaccess_end(); |
| return ret; |
| } |
| } |
| -- |
| cgit 1.2-0.3.lf.el7 |
| |
| From 98ce99aa23b43c3dc736cd0354537fca029d69cb Mon Sep 17 00:00:00 2001 |
| From: Dan Williams <dan.j.williams@intel.com> |
| Date: Mon, 29 Jan 2018 17:02:49 -0800 |
| Subject: x86/uaccess: Use __uaccess_begin_nospec() and uaccess_try_nospec |
| |
| 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@dwillia2-desk3.amr.corp.intel.com |
| [bwh: Backported to 3.16: |
| - Convert several more functions to use __uaccess_begin_nospec(), that |
| are just wrappers in mainline |
| - There's no 'case 8' in __copy_to_user_inatomic() |
| - Adjust context] |
| Signed-off-by: Ben Hutchings <ben@decadent.org.uk> |
| |
| arch/x86/include/asm/uaccess.h | 6 +++--- |
| arch/x86/include/asm/uaccess_32.h | 24 ++++++++++++------------ |
| arch/x86/include/asm/uaccess_64.h | 20 ++++++++++---------- |
| arch/x86/lib/usercopy_32.c | 10 +++++----- |
| 4 files changed, 30 insertions(+), 30 deletions(-) |
| |
| diff --git a/arch/x86/include/asm/uaccess_32.h b/arch/x86/include/asm/uaccess_32.h |
| index b25d109fb95a..c803818cedfb 100644 |
| |
| |
| @@ -48,19 +48,19 @@ __copy_to_user_inatomic(void __user *to, const void *from, unsigned long n) |
| |
| 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(); |
| @@ -104,17 +104,17 @@ __copy_from_user_inatomic(void *to, const void __user *from, unsigned long n) |
| |
| 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; |
| @@ -154,17 +154,17 @@ __copy_from_user(void *to, const void __user *from, unsigned long n) |
| |
| 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; |
| @@ -182,17 +182,17 @@ static __always_inline unsigned long __copy_from_user_nocache(void *to, |
| |
| 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; |
| diff --git a/arch/x86/lib/usercopy_32.c b/arch/x86/lib/usercopy_32.c |
| index 7f6e7dd46215..de848bc95a9f 100644 |
| |
| |
| @@ -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 |
| -- |
| cgit 1.2-0.3.lf.el7 |
| |