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[93.17.236.30]) by mx.google.com with ESMTPS id g1si55416782wrv.204.2019.01.16.08.59.28 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Wed, 16 Jan 2019 08:59:28 -0800 (PST) Received-SPF: pass (google.com: domain of christophe.leroy@c-s.fr designates 93.17.236.30 as permitted sender) client-ip=93.17.236.30; Authentication-Results: mx.google.com; dkim=pass header.i=@c-s.fr header.s=mail header.b=eLvAt7Bq; spf=pass (google.com: domain of christophe.leroy@c-s.fr designates 93.17.236.30 as permitted sender) smtp.mailfrom=christophe.leroy@c-s.fr Received: from localhost (mailhub1-int [192.168.12.234]) by localhost (Postfix) with ESMTP id 43ftjB4Kcjz9vBmN; Wed, 16 Jan 2019 17:59:26 +0100 (CET) Authentication-Results: localhost; dkim=pass reason="1024-bit key; insecure key" header.d=c-s.fr header.i=@c-s.fr header.b=eLvAt7Bq; dkim-adsp=pass; dkim-atps=neutral X-Virus-Scanned: Debian amavisd-new at c-s.fr Received: from pegase1.c-s.fr ([192.168.12.234]) by localhost (pegase1.c-s.fr [192.168.12.234]) (amavisd-new, port 10024) with ESMTP id 1y33t7ubUemJ; Wed, 16 Jan 2019 17:59:26 +0100 (CET) Received: from messagerie.si.c-s.fr (messagerie.si.c-s.fr [192.168.25.192]) by pegase1.c-s.fr (Postfix) with ESMTP id 43ftjB3GBBz9vBmJ; Wed, 16 Jan 2019 17:59:26 +0100 (CET) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=c-s.fr; s=mail; t=1547657966; bh=VClA1koYN/8UB1kz/FeELweQ5cMzF1pBl+1hJ48rHrs=; h=From:Subject:To:Cc:Date:From; b=eLvAt7BqtYsxN7kNzsTn3yCzQeJgXW/pvrjCRLWQQ+Rx6by4eR4OaEJxaMf4xrbET FQPUhr3MjsHuIZLRxf2Pz0xRhQ1V3U3082He6sRkmK9YzwfMpNOArgKFNnb2OSCtzl KimuUtlrI8GCG37yM7y6uPutILgDbNlGXG28AO5Q= Received: from localhost (localhost [127.0.0.1]) by messagerie.si.c-s.fr (Postfix) with ESMTP id 0E9D68B84C; Wed, 16 Jan 2019 17:59:28 +0100 (CET) X-Virus-Scanned: amavisd-new at c-s.fr Received: from messagerie.si.c-s.fr ([127.0.0.1]) by localhost (messagerie.si.c-s.fr [127.0.0.1]) (amavisd-new, port 10023) with ESMTP id 2W1rUcGyGM6V; Wed, 16 Jan 2019 17:59:27 +0100 (CET) Received: from po16846vm.idsi0.si.c-s.fr (unknown [192.168.4.90]) by messagerie.si.c-s.fr (Postfix) with ESMTP id C98BD8B848; Wed, 16 Jan 2019 17:59:27 +0100 (CET) Received: by po16846vm.idsi0.si.c-s.fr (Postfix, from userid 0) id 6A6F37187C; Wed, 16 Jan 2019 16:59:27 +0000 (UTC) Message-Id: <39fb6c5a191025378676492e140dc012915ecaeb.1547652372.git.christophe.leroy@c-s.fr> From: Christophe Leroy Subject: [PATCH v3 1/2] mm: add probe_user_read() To: Kees Cook , Andrew Morton , Benjamin Herrenschmidt , Paul Mackerras , Michael Ellerman , Mike Rapoport Cc: linux-kernel@vger.kernel.org, linuxppc-dev@lists.ozlabs.org, linux-mm@kvack.org Date: Wed, 16 Jan 2019 16:59:27 +0000 (UTC) X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: X-Virus-Scanned: ClamAV using ClamSMTP In powerpc code, there are several places implementing safe access to user data. This is sometimes implemented using probe_kernel_address() with additional access_ok() verification, sometimes with get_user() enclosed in a pagefault_disable()/enable() pair, etc. : show_user_instructions() bad_stack_expansion() p9_hmi_special_emu() fsl_pci_mcheck_exception() read_user_stack_64() read_user_stack_32() on PPC64 read_user_stack_32() on PPC32 power_pmu_bhrb_to() In the same spirit as probe_kernel_read(), this patch adds probe_user_read(). probe_user_read() does the same as probe_kernel_read() but first checks that it is really a user address. The patch defines this function as a static inline so the "size" variable can be examined for const-ness by the check_object_size() in __copy_from_user_inatomic() Signed-off-by: Christophe Leroy Acked-by: Murilo Opsfelder Araujo --- v3: Moved 'Returns:" comment after description. Explained in the commit log why the function is defined static inline v2: Added "Returns:" comment and removed probe_user_address() include/linux/uaccess.h | 34 ++++++++++++++++++++++++++++++++++ 1 file changed, 34 insertions(+) diff --git a/include/linux/uaccess.h b/include/linux/uaccess.h index 37b226e8df13..ef99edd63da3 100644 --- a/include/linux/uaccess.h +++ b/include/linux/uaccess.h @@ -263,6 +263,40 @@ extern long strncpy_from_unsafe(char *dst, const void *unsafe_addr, long count); #define probe_kernel_address(addr, retval) \ probe_kernel_read(&retval, addr, sizeof(retval)) +/** + * probe_user_read(): safely attempt to read from a user location + * @dst: pointer to the buffer that shall take the data + * @src: address to read from + * @size: size of the data chunk + * + * Safely read from address @src to the buffer at @dst. If a kernel fault + * happens, handle that and return -EFAULT. + * + * We ensure that the copy_from_user is executed in atomic context so that + * do_page_fault() doesn't attempt to take mmap_sem. This makes + * probe_user_read() suitable for use within regions where the caller + * already holds mmap_sem, or other locks which nest inside mmap_sem. + * + * Returns: 0 on success, -EFAULT on error. + */ + +#ifndef probe_user_read +static __always_inline long probe_user_read(void *dst, const void __user *src, + size_t size) +{ + long ret; + + if (!access_ok(src, size)) + return -EFAULT; + + pagefault_disable(); + ret = __copy_from_user_inatomic(dst, src, size); + pagefault_enable(); + + return ret ? -EFAULT : 0; +} +#endif + #ifndef user_access_begin #define user_access_begin(ptr,len) access_ok(ptr, len) #define user_access_end() do { } while (0)