From: Dan Williams <dan.j.williams@intel.com> To: linux-kernel@vger.kernel.org Cc: linux-arch@vger.kernel.org, Andi Kleen <ak@linux.intel.com>, Kees Cook <keescook@chromium.org>, kernel-hardening@lists.openwall.com, gregkh@linuxfoundation.org, x86@kernel.org, Ingo Molnar <mingo@redhat.com>, Al Viro <viro@zeniv.linux.org.uk>, "H. Peter Anvin" <hpa@zytor.com>, tglx@linutronix.de, torvalds@linux-foundation.org, akpm@linux-foundation.org, alan@linux.intel.com Subject: [PATCH v4 05/10] x86, __get_user: use __uaccess_begin_nospec Date: Thu, 18 Jan 2018 16:02:09 -0800 [thread overview] Message-ID: <151632012423.21271.2067397758879498193.stgit@dwillia2-desk3.amr.corp.intel.com> (raw) In-Reply-To: <151632009605.21271.11304291057104672116.stgit@dwillia2-desk3.amr.corp.intel.com> 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 an 'lfence' prevents speculation with a potential pointer to privileged memory. Suggested-by: Linus Torvalds <torvalds@linux-foundation.org> Suggested-by: Andi Kleen <ak@linux.intel.com> Cc: Al Viro <viro@zeniv.linux.org.uk> Cc: Kees Cook <keescook@chromium.org> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: "H. Peter Anvin" <hpa@zytor.com> Cc: Ingo Molnar <mingo@redhat.com> Cc: x86@kernel.org Signed-off-by: Dan Williams <dan.j.williams@intel.com> --- arch/x86/include/asm/uaccess.h | 6 +++--- arch/x86/include/asm/uaccess_32.h | 6 +++--- arch/x86/include/asm/uaccess_64.h | 12 ++++++------ arch/x86/lib/usercopy_32.c | 8 ++++---- 4 files changed, 16 insertions(+), 16 deletions(-) diff --git a/arch/x86/include/asm/uaccess.h b/arch/x86/include/asm/uaccess.h index 626caf58183a..a930585fa3b5 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: \ { \ 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(); diff --git a/arch/x86/include/asm/uaccess_64.h b/arch/x86/include/asm/uaccess_64.h index f07ef3c575db..62546b3a398e 100644 --- a/arch/x86/include/asm/uaccess_64.h +++ b/arch/x86/include/asm/uaccess_64.h @@ -55,31 +55,31 @@ raw_copy_from_user(void *dst, const void __user *src, unsigned long size) return copy_user_generic(dst, (__force void *)src, size); switch (size) { case 1: - __uaccess_begin(); + __uaccess_begin_nospec(); __get_user_asm_nozero(*(u8 *)dst, (u8 __user *)src, ret, "b", "b", "=q", 1); __uaccess_end(); return ret; case 2: - __uaccess_begin(); + __uaccess_begin_nospec(); __get_user_asm_nozero(*(u16 *)dst, (u16 __user *)src, ret, "w", "w", "=r", 2); __uaccess_end(); return ret; case 4: - __uaccess_begin(); + __uaccess_begin_nospec(); __get_user_asm_nozero(*(u32 *)dst, (u32 __user *)src, ret, "l", "k", "=r", 4); __uaccess_end(); return ret; case 8: - __uaccess_begin(); + __uaccess_begin_nospec(); __get_user_asm_nozero(*(u64 *)dst, (u64 __user *)src, ret, "q", "", "=r", 8); __uaccess_end(); return ret; case 10: - __uaccess_begin(); + __uaccess_begin_nospec(); __get_user_asm_nozero(*(u64 *)dst, (u64 __user *)src, ret, "q", "", "=r", 10); if (likely(!ret)) @@ -89,7 +89,7 @@ raw_copy_from_user(void *dst, const void __user *src, unsigned long size) __uaccess_end(); return ret; case 16: - __uaccess_begin(); + __uaccess_begin_nospec(); __get_user_asm_nozero(*(u64 *)dst, (u64 __user *)src, ret, "q", "", "=r", 16); if (likely(!ret)) diff --git a/arch/x86/lib/usercopy_32.c b/arch/x86/lib/usercopy_32.c index 1b377f734e64..7add8ba06887 100644 --- a/arch/x86/lib/usercopy_32.c +++ b/arch/x86/lib/usercopy_32.c @@ -331,12 +331,12 @@ do { \ unsigned long __copy_user_ll(void *to, const void *from, unsigned long n) { - stac(); + __uaccess_begin_nospec(); if (movsl_is_ok(to, from, n)) __copy_user(to, from, n); else n = __copy_user_intel(to, from, n); - clac(); + __uaccess_end(); return n; } EXPORT_SYMBOL(__copy_user_ll); @@ -344,7 +344,7 @@ EXPORT_SYMBOL(__copy_user_ll); unsigned long __copy_from_user_ll_nocache_nozero(void *to, const void __user *from, unsigned long n) { - stac(); + __uaccess_begin_nospec(); #ifdef CONFIG_X86_INTEL_USERCOPY if (n > 64 && static_cpu_has(X86_FEATURE_XMM2)) n = __copy_user_intel_nocache(to, from, n); @@ -353,7 +353,7 @@ unsigned long __copy_from_user_ll_nocache_nozero(void *to, const void __user *fr #else __copy_user(to, from, n); #endif - clac(); + __uaccess_end(); return n; } EXPORT_SYMBOL(__copy_from_user_ll_nocache_nozero);
WARNING: multiple messages have this Message-ID (diff)
From: Dan Williams <dan.j.williams@intel.com> To: linux-kernel@vger.kernel.org Cc: linux-arch@vger.kernel.org, Andi Kleen <ak@linux.intel.com>, Kees Cook <keescook@chromium.org>, kernel-hardening@lists.openwall.com, gregkh@linuxfoundation.org, x86@kernel.org, Ingo Molnar <mingo@redhat.com>, Al Viro <viro@zeniv.linux.org.uk>, "H. Peter Anvin" <hpa@zytor.com>, tglx@linutronix.de, torvalds@linux-foundation.org, akpm@linux-foundation.org, alan@linux.intel.com Subject: [kernel-hardening] [PATCH v4 05/10] x86, __get_user: use __uaccess_begin_nospec Date: Thu, 18 Jan 2018 16:02:09 -0800 [thread overview] Message-ID: <151632012423.21271.2067397758879498193.stgit@dwillia2-desk3.amr.corp.intel.com> (raw) In-Reply-To: <151632009605.21271.11304291057104672116.stgit@dwillia2-desk3.amr.corp.intel.com> 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 an 'lfence' prevents speculation with a potential pointer to privileged memory. Suggested-by: Linus Torvalds <torvalds@linux-foundation.org> Suggested-by: Andi Kleen <ak@linux.intel.com> Cc: Al Viro <viro@zeniv.linux.org.uk> Cc: Kees Cook <keescook@chromium.org> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: "H. Peter Anvin" <hpa@zytor.com> Cc: Ingo Molnar <mingo@redhat.com> Cc: x86@kernel.org Signed-off-by: Dan Williams <dan.j.williams@intel.com> --- arch/x86/include/asm/uaccess.h | 6 +++--- arch/x86/include/asm/uaccess_32.h | 6 +++--- arch/x86/include/asm/uaccess_64.h | 12 ++++++------ arch/x86/lib/usercopy_32.c | 8 ++++---- 4 files changed, 16 insertions(+), 16 deletions(-) diff --git a/arch/x86/include/asm/uaccess.h b/arch/x86/include/asm/uaccess.h index 626caf58183a..a930585fa3b5 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: \ { \ 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(); diff --git a/arch/x86/include/asm/uaccess_64.h b/arch/x86/include/asm/uaccess_64.h index f07ef3c575db..62546b3a398e 100644 --- a/arch/x86/include/asm/uaccess_64.h +++ b/arch/x86/include/asm/uaccess_64.h @@ -55,31 +55,31 @@ raw_copy_from_user(void *dst, const void __user *src, unsigned long size) return copy_user_generic(dst, (__force void *)src, size); switch (size) { case 1: - __uaccess_begin(); + __uaccess_begin_nospec(); __get_user_asm_nozero(*(u8 *)dst, (u8 __user *)src, ret, "b", "b", "=q", 1); __uaccess_end(); return ret; case 2: - __uaccess_begin(); + __uaccess_begin_nospec(); __get_user_asm_nozero(*(u16 *)dst, (u16 __user *)src, ret, "w", "w", "=r", 2); __uaccess_end(); return ret; case 4: - __uaccess_begin(); + __uaccess_begin_nospec(); __get_user_asm_nozero(*(u32 *)dst, (u32 __user *)src, ret, "l", "k", "=r", 4); __uaccess_end(); return ret; case 8: - __uaccess_begin(); + __uaccess_begin_nospec(); __get_user_asm_nozero(*(u64 *)dst, (u64 __user *)src, ret, "q", "", "=r", 8); __uaccess_end(); return ret; case 10: - __uaccess_begin(); + __uaccess_begin_nospec(); __get_user_asm_nozero(*(u64 *)dst, (u64 __user *)src, ret, "q", "", "=r", 10); if (likely(!ret)) @@ -89,7 +89,7 @@ raw_copy_from_user(void *dst, const void __user *src, unsigned long size) __uaccess_end(); return ret; case 16: - __uaccess_begin(); + __uaccess_begin_nospec(); __get_user_asm_nozero(*(u64 *)dst, (u64 __user *)src, ret, "q", "", "=r", 16); if (likely(!ret)) diff --git a/arch/x86/lib/usercopy_32.c b/arch/x86/lib/usercopy_32.c index 1b377f734e64..7add8ba06887 100644 --- a/arch/x86/lib/usercopy_32.c +++ b/arch/x86/lib/usercopy_32.c @@ -331,12 +331,12 @@ do { \ unsigned long __copy_user_ll(void *to, const void *from, unsigned long n) { - stac(); + __uaccess_begin_nospec(); if (movsl_is_ok(to, from, n)) __copy_user(to, from, n); else n = __copy_user_intel(to, from, n); - clac(); + __uaccess_end(); return n; } EXPORT_SYMBOL(__copy_user_ll); @@ -344,7 +344,7 @@ EXPORT_SYMBOL(__copy_user_ll); unsigned long __copy_from_user_ll_nocache_nozero(void *to, const void __user *from, unsigned long n) { - stac(); + __uaccess_begin_nospec(); #ifdef CONFIG_X86_INTEL_USERCOPY if (n > 64 && static_cpu_has(X86_FEATURE_XMM2)) n = __copy_user_intel_nocache(to, from, n); @@ -353,7 +353,7 @@ unsigned long __copy_from_user_ll_nocache_nozero(void *to, const void __user *fr #else __copy_user(to, from, n); #endif - clac(); + __uaccess_end(); return n; } EXPORT_SYMBOL(__copy_from_user_ll_nocache_nozero);
next prev parent reply other threads:[~2018-01-19 0:02 UTC|newest] Thread overview: 70+ messages / expand[flat|nested] mbox.gz Atom feed top 2018-01-19 0:01 [PATCH v4 00/10] prevent bounds-check bypass via speculative execution Dan Williams 2018-01-19 0:01 ` [kernel-hardening] " Dan Williams 2018-01-19 0:01 ` Dan Williams 2018-01-19 0:01 ` [PATCH v4 01/10] Documentation: document array_ptr Dan Williams 2018-01-19 0:01 ` [kernel-hardening] " Dan Williams 2018-01-19 0:01 ` [PATCH v4 02/10] asm/nospec, array_ptr: sanitize speculative array de-references Dan Williams 2018-01-19 0:01 ` [kernel-hardening] " Dan Williams 2018-01-19 10:20 ` Jann Horn 2018-01-19 17:48 ` Adam Sampson 2018-01-19 17:48 ` Adam Sampson 2018-01-19 17:48 ` Adam Sampson 2018-01-19 17:48 ` Adam Sampson 2018-01-19 18:12 ` Dan Williams 2018-01-19 18:18 ` Will Deacon 2018-01-19 18:18 ` Will Deacon 2018-01-19 18:26 ` [kernel-hardening] " Dan Williams 2018-01-19 18:18 ` Linus Torvalds 2018-01-19 18:18 ` Linus Torvalds 2018-01-19 20:55 ` [kernel-hardening] " Dan Williams 2018-01-25 7:09 ` Cyril Novikov 2018-01-25 7:09 ` [kernel-hardening] " Cyril Novikov 2018-01-25 22:37 ` Dan Williams 2018-01-25 22:37 ` [kernel-hardening] " Dan Williams 2018-01-19 0:01 ` [PATCH v4 03/10] x86: implement array_ptr_mask() Dan Williams 2018-01-19 0:01 ` [kernel-hardening] " Dan Williams 2018-01-19 0:01 ` [PATCH v4 04/10] x86: introduce __uaccess_begin_nospec and ifence Dan Williams 2018-01-19 0:01 ` [kernel-hardening] " Dan Williams 2018-01-19 0:02 ` Dan Williams [this message] 2018-01-19 0:02 ` [kernel-hardening] [PATCH v4 05/10] x86, __get_user: use __uaccess_begin_nospec Dan Williams 2018-01-19 0:02 ` [PATCH v4 06/10] x86, get_user: use pointer masking to limit speculation Dan Williams 2018-01-19 0:02 ` [kernel-hardening] " Dan Williams 2018-01-19 0:02 ` [PATCH v4 07/10] x86: narrow out of bounds syscalls to sys_read under speculation Dan Williams 2018-01-19 0:02 ` [kernel-hardening] " Dan Williams 2018-01-24 14:40 ` Jiri Slaby 2018-01-24 14:40 ` [kernel-hardening] " Jiri Slaby 2018-02-06 19:29 ` Luis Henriques 2018-02-06 19:48 ` Dan Williams 2018-02-06 20:26 ` Linus Torvalds 2018-02-06 20:37 ` Dan Williams 2018-02-06 20:42 ` Linus Torvalds 2018-02-06 20:43 ` Linus Torvalds 2018-02-06 20:49 ` Andy Lutomirski 2018-02-06 20:58 ` Linus Torvalds 2018-02-06 21:37 ` Dan Williams 2018-02-06 22:52 ` Linus Torvalds 2018-02-07 0:33 ` Dan Williams 2018-02-07 1:23 ` Linus Torvalds 2018-02-06 22:51 ` Luis Henriques 2018-02-06 22:51 ` Luis Henriques 2018-01-19 0:02 ` [PATCH v4 08/10] vfs, fdtable: prevent bounds-check bypass via speculative execution Dan Williams 2018-01-19 0:02 ` [kernel-hardening] " Dan Williams 2018-01-19 0:02 ` [PATCH v4 09/10] kvm, x86: fix spectre-v1 mitigation Dan Williams 2018-01-19 0:02 ` [kernel-hardening] " Dan Williams 2018-01-19 8:42 ` Paolo Bonzini 2018-01-19 8:42 ` [kernel-hardening] " Paolo Bonzini 2018-01-19 0:02 ` [PATCH v4 10/10] nl80211: sanitize array index in parse_txq_params Dan Williams 2018-01-19 0:02 ` [kernel-hardening] " Dan Williams 2018-01-19 0:02 ` Dan Williams 2018-01-21 10:37 ` Johannes Berg 2018-01-21 10:37 ` [kernel-hardening] " Johannes Berg 2018-01-21 10:37 ` Johannes Berg 2018-01-20 6:58 ` [PATCH v4 00/10] prevent bounds-check bypass via speculative execution Dan Williams 2018-01-20 6:58 ` [kernel-hardening] " Dan Williams 2018-01-20 6:58 ` Dan Williams 2018-01-20 16:56 ` Alexei Starovoitov 2018-01-20 16:56 ` [kernel-hardening] " Alexei Starovoitov 2018-01-20 16:56 ` Alexei Starovoitov 2018-01-20 17:07 ` Alexei Starovoitov 2018-01-20 17:07 ` [kernel-hardening] " Alexei Starovoitov 2018-01-20 17:07 ` Alexei Starovoitov
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