From: Dan Williams <dan.j.williams@intel.com> To: linux-kernel@vger.kernel.org Cc: linux-arch@vger.kernel.org, kernel-hardening@lists.openwall.com, gregkh@linuxfoundation.org, x86@kernel.org, Ingo Molnar <mingo@redhat.com>, "H. Peter Anvin" <hpa@zytor.com>, tglx@linutronix.de, torvalds@linux-foundation.org, akpm@linux-foundation.org, alan@linux.intel.com Subject: [PATCH v4 03/10] x86: implement array_ptr_mask() Date: Thu, 18 Jan 2018 16:01:52 -0800 [thread overview] Message-ID: <151632011276.21271.6230510107230588371.stgit@dwillia2-desk3.amr.corp.intel.com> (raw) In-Reply-To: <151632009605.21271.11304291057104672116.stgit@dwillia2-desk3.amr.corp.intel.com> 'array_ptr' uses a mask to sanitize user controllable pointers. The x86 'array_ptr_mask' is an assembler optimized way to generate a 0 or ~0 mask if an array index is out-of-bounds or in-bounds. Suggested-by: Linus Torvalds <torvalds@linux-foundation.org> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: Ingo Molnar <mingo@redhat.com> Cc: "H. Peter Anvin" <hpa@zytor.com> Cc: x86@kernel.org Signed-off-by: Dan Williams <dan.j.williams@intel.com> --- arch/x86/include/asm/barrier.h | 24 ++++++++++++++++++++++++ 1 file changed, 24 insertions(+) diff --git a/arch/x86/include/asm/barrier.h b/arch/x86/include/asm/barrier.h index 7fb336210e1b..67f6d4707a2c 100644 --- a/arch/x86/include/asm/barrier.h +++ b/arch/x86/include/asm/barrier.h @@ -24,6 +24,30 @@ #define wmb() asm volatile("sfence" ::: "memory") #endif +/** + * array_ptr_mask - generate a mask for array_ptr() that is ~0UL when + * the bounds check succeeds and 0 otherwise + */ +#define array_ptr_mask array_ptr_mask +static inline unsigned long array_ptr_mask(unsigned long idx, unsigned long sz) +{ + unsigned long mask; + + /* + * mask = index - size, if that result is >= 0 then the index is + * invalid and the mask is 0 else ~0 + */ +#ifdef CONFIG_X86_32 + asm ("cmpl %1,%2; sbbl %0,%0;" +#else + asm ("cmpq %1,%2; sbbq %0,%0;" +#endif + :"=r" (mask) + :"r"(sz),"r" (idx) + :"cc"); + return mask; +} + #ifdef CONFIG_X86_PPRO_FENCE #define dma_rmb() rmb() #else
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, kernel-hardening@lists.openwall.com, gregkh@linuxfoundation.org, x86@kernel.org, Ingo Molnar <mingo@redhat.com>, "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 03/10] x86: implement array_ptr_mask() Date: Thu, 18 Jan 2018 16:01:52 -0800 [thread overview] Message-ID: <151632011276.21271.6230510107230588371.stgit@dwillia2-desk3.amr.corp.intel.com> (raw) In-Reply-To: <151632009605.21271.11304291057104672116.stgit@dwillia2-desk3.amr.corp.intel.com> 'array_ptr' uses a mask to sanitize user controllable pointers. The x86 'array_ptr_mask' is an assembler optimized way to generate a 0 or ~0 mask if an array index is out-of-bounds or in-bounds. Suggested-by: Linus Torvalds <torvalds@linux-foundation.org> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: Ingo Molnar <mingo@redhat.com> Cc: "H. Peter Anvin" <hpa@zytor.com> Cc: x86@kernel.org Signed-off-by: Dan Williams <dan.j.williams@intel.com> --- arch/x86/include/asm/barrier.h | 24 ++++++++++++++++++++++++ 1 file changed, 24 insertions(+) diff --git a/arch/x86/include/asm/barrier.h b/arch/x86/include/asm/barrier.h index 7fb336210e1b..67f6d4707a2c 100644 --- a/arch/x86/include/asm/barrier.h +++ b/arch/x86/include/asm/barrier.h @@ -24,6 +24,30 @@ #define wmb() asm volatile("sfence" ::: "memory") #endif +/** + * array_ptr_mask - generate a mask for array_ptr() that is ~0UL when + * the bounds check succeeds and 0 otherwise + */ +#define array_ptr_mask array_ptr_mask +static inline unsigned long array_ptr_mask(unsigned long idx, unsigned long sz) +{ + unsigned long mask; + + /* + * mask = index - size, if that result is >= 0 then the index is + * invalid and the mask is 0 else ~0 + */ +#ifdef CONFIG_X86_32 + asm ("cmpl %1,%2; sbbl %0,%0;" +#else + asm ("cmpq %1,%2; sbbq %0,%0;" +#endif + :"=r" (mask) + :"r"(sz),"r" (idx) + :"cc"); + return mask; +} + #ifdef CONFIG_X86_PPRO_FENCE #define dma_rmb() rmb() #else
next prev parent reply other threads:[~2018-01-19 0:01 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 ` Dan Williams [this message] 2018-01-19 0:01 ` [kernel-hardening] [PATCH v4 03/10] x86: implement array_ptr_mask() 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 ` [PATCH v4 05/10] x86, __get_user: use __uaccess_begin_nospec Dan Williams 2018-01-19 0:02 ` [kernel-hardening] " 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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