From mboxrd@z Thu Jan 1 00:00:00 1970 From: Igor Stoppa Subject: [RFC PATCH v4 02/12] __wr_after_init: x86_64: memset_user() Date: Tue, 12 Feb 2019 01:27:39 +0200 Message-Id: In-Reply-To: References: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Cc: Igor Stoppa , Andy Lutomirski , Nadav Amit , Matthew Wilcox , Peter Zijlstra , Kees Cook , Dave Hansen , Mimi Zohar , Thiago Jung Bauermann , Ahmed Soliman , linux-integrity@vger.kernel.org, kernel-hardening@lists.openwall.com, linux-mm@kvack.org, linux-kernel@vger.kernel.org List-ID: x86_64 specific version of memset() for user space, memset_user() In the __wr_after_init scenario, write-rare variables have: - a primary read-only mapping in kernel memory space - an alternate, writable mapping, implemented as user-space mapping The write rare implementation expects the arch code to privide a memset_user() function, which is currently missing. clear_user() is the base for memset_user() Signed-off-by: Igor Stoppa CC: Andy Lutomirski CC: Nadav Amit CC: Matthew Wilcox CC: Peter Zijlstra CC: Kees Cook CC: Dave Hansen CC: Mimi Zohar CC: Thiago Jung Bauermann CC: Ahmed Soliman CC: linux-integrity@vger.kernel.org CC: kernel-hardening@lists.openwall.com CC: linux-mm@kvack.org CC: linux-kernel@vger.kernel.org --- arch/x86/include/asm/uaccess_64.h | 6 ++++ arch/x86/lib/usercopy_64.c | 51 +++++++++++++++++++++++++++++++++ 2 files changed, 57 insertions(+) diff --git a/arch/x86/include/asm/uaccess_64.h b/arch/x86/include/asm/uaccess_64.h index a9d637bc301d..f194bfce4866 100644 --- a/arch/x86/include/asm/uaccess_64.h +++ b/arch/x86/include/asm/uaccess_64.h @@ -213,4 +213,10 @@ copy_user_handle_tail(char *to, char *from, unsigned len); unsigned long mcsafe_handle_tail(char *to, char *from, unsigned len); +unsigned long __must_check +memset_user(void __user *mem, int c, unsigned long len); + +unsigned long __must_check +__memset_user(void __user *mem, int c, unsigned long len); + #endif /* _ASM_X86_UACCESS_64_H */ diff --git a/arch/x86/lib/usercopy_64.c b/arch/x86/lib/usercopy_64.c index ee42bb0cbeb3..e61963585354 100644 --- a/arch/x86/lib/usercopy_64.c +++ b/arch/x86/lib/usercopy_64.c @@ -9,6 +9,57 @@ #include #include +/* + * Memset Userspace + */ + +unsigned long __memset_user(void __user *addr, int c, unsigned long size) +{ + long __d0; + unsigned long pattern = 0x0101010101010101UL * (0xFFUL & c); + + might_fault(); + /* no memory constraint: gcc doesn't know about this memory */ + stac(); + asm volatile( + " movq %[pattern], %%rdx\n" + " testq %[size8],%[size8]\n" + " jz 4f\n" + "0: mov %%rdx,(%[dst])\n" + " addq $8,%[dst]\n" + " decl %%ecx ; jnz 0b\n" + "4: movq %[size1],%%rcx\n" + " testl %%ecx,%%ecx\n" + " jz 2f\n" + "1: movb %%dl,(%[dst])\n" + " incq %[dst]\n" + " decl %%ecx ; jnz 1b\n" + "2:\n" + ".section .fixup,\"ax\"\n" + "3: lea 0(%[size1],%[size8],8),%[size8]\n" + " jmp 2b\n" + ".previous\n" + _ASM_EXTABLE_UA(0b, 3b) + _ASM_EXTABLE_UA(1b, 2b) + : [size8] "=&c"(size), [dst] "=&D" (__d0) + : [size1] "r" (size & 7), "[size8]" (size / 8), + "[dst]" (addr), [pattern] "r" (pattern) + : "rdx"); + + clac(); + return size; +} +EXPORT_SYMBOL(__memset_user); + +unsigned long memset_user(void __user *to, int c, unsigned long n) +{ + if (access_ok(to, n)) + return __memset_user(to, c, n); + return n; +} +EXPORT_SYMBOL(memset_user); + + /* * Zero Userspace */ -- 2.19.1