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[2.15.159.20]) by smtp.gmail.com with ESMTPSA id q4sm11983375wru.65.2020.09.04.08.46.33 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 04 Sep 2020 08:46:34 -0700 (PDT) From: Bartosz Golaszewski To: Linus Walleij , Jonathan Corbet , Mika Westerberg , Andy Shevchenko , Kent Gibson Cc: linux-gpio@vger.kernel.org, linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org, linux-acpi@vger.kernel.org, Bartosz Golaszewski Subject: [PATCH 03/23] lib: uaccess: provide getline_from_user() Date: Fri, 4 Sep 2020 17:45:27 +0200 Message-Id: <20200904154547.3836-4-brgl@bgdev.pl> X-Mailer: git-send-email 2.26.1 In-Reply-To: <20200904154547.3836-1-brgl@bgdev.pl> References: <20200904154547.3836-1-brgl@bgdev.pl> MIME-Version: 1.0 Sender: linux-gpio-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-gpio@vger.kernel.org From: Bartosz Golaszewski Provide a uaccess helper that allows callers to copy a single line from user memory. This is useful for debugfs write callbacks. Signed-off-by: Bartosz Golaszewski --- include/linux/uaccess.h | 3 +++ lib/usercopy.c | 37 +++++++++++++++++++++++++++++++++++++ 2 files changed, 40 insertions(+) diff --git a/include/linux/uaccess.h b/include/linux/uaccess.h index 94b285411659..5aedd8ac5c31 100644 --- a/include/linux/uaccess.h +++ b/include/linux/uaccess.h @@ -333,6 +333,9 @@ long strncpy_from_user_nofault(char *dst, const void __user *unsafe_addr, long count); long strnlen_user_nofault(const void __user *unsafe_addr, long count); +ssize_t getline_from_user(char *dst, size_t dst_size, + const char __user *src, size_t src_size); + /** * get_kernel_nofault(): safely attempt to read from a location * @val: read into this variable diff --git a/lib/usercopy.c b/lib/usercopy.c index b26509f112f9..55aaaf93d847 100644 --- a/lib/usercopy.c +++ b/lib/usercopy.c @@ -87,3 +87,40 @@ int check_zeroed_user(const void __user *from, size_t size) return -EFAULT; } EXPORT_SYMBOL(check_zeroed_user); + +/** + * getline_from_user - Copy a single line from user + * @dst: Where to copy the line to + * @dst_size: Size of the destination buffer + * @src: Where to copy the line from + * @src_size: Size of the source user buffer + * + * Copies a number of characters from given user buffer into the dst buffer. + * The number of bytes is limited to the lesser of the sizes of both buffers. + * If the copied string contains a newline, its first occurrence is replaced + * by a NULL byte in the destination buffer. Otherwise the function ensures + * the copied string is NULL-terminated. + * + * Returns the number of copied bytes or a negative error number on failure. + */ + +ssize_t getline_from_user(char *dst, size_t dst_size, + const char __user *src, size_t src_size) +{ + size_t size = min_t(size_t, dst_size, src_size); + char *c; + int ret; + + ret = copy_from_user(dst, src, size); + if (ret) + return -EFAULT; + + dst[size - 1] = '\0'; + + c = strchrnul(dst, '\n'); + if (*c) + *c = '\0'; + + return c - dst; +} +EXPORT_SYMBOL(getline_from_user);