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Registered in England and Wales under Company Registration No. 3798903 Subject: [PATCH 01/14] Provide a function to create a NUL-terminated string from unterminated data [ver #2] From: David Howells To: mszeredi@redhat.com, viro@zeniv.linux.org.uk, jlayton@redhat.com Cc: dhowells@redhat.com, linux-fsdevel@vger.kernel.org, linux-nfs@vger.kernel.org, linux-kernel@vger.kernel.org Date: Thu, 11 May 2017 14:59:54 +0100 Message-ID: <149451119460.4599.10924646742411868045.stgit@warthog.procyon.org.uk> In-Reply-To: <149451118535.4599.16084557087363834548.stgit@warthog.procyon.org.uk> References: <149451118535.4599.16084557087363834548.stgit@warthog.procyon.org.uk> User-Agent: StGit/0.17.1-dirty MIME-Version: 1.0 X-Scanned-By: MIMEDefang 2.79 on 10.5.11.16 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.29]); Thu, 11 May 2017 13:59:56 +0000 (UTC) Sender: linux-fsdevel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-fsdevel@vger.kernel.org X-Virus-Scanned: ClamAV using ClamSMTP Provide a function, kmemdup_nul(), that will create a NUL-terminated string from an unterminated character array where the length is known in advance. This is better than kstrndup() in situations where we already know the string length as the strnlen() in kstrndup() is superfluous. Signed-off-by: David Howells --- include/linux/string.h | 1 + mm/util.c | 24 ++++++++++++++++++++++++ 2 files changed, 25 insertions(+) diff --git a/include/linux/string.h b/include/linux/string.h index 26b6f6a66f83..0c88c0a1a72b 100644 --- a/include/linux/string.h +++ b/include/linux/string.h @@ -123,6 +123,7 @@ extern char *kstrdup(const char *s, gfp_t gfp) __malloc; extern const char *kstrdup_const(const char *s, gfp_t gfp); extern char *kstrndup(const char *s, size_t len, gfp_t gfp); extern void *kmemdup(const void *src, size_t len, gfp_t gfp); +extern char *kmemdup_nul(const char *s, size_t len, gfp_t gfp); extern char **argv_split(gfp_t gfp, const char *str, int *argcp); extern void argv_free(char **argv); diff --git a/mm/util.c b/mm/util.c index 656dc5e37a87..be68664bfb73 100644 --- a/mm/util.c +++ b/mm/util.c @@ -83,6 +83,8 @@ EXPORT_SYMBOL(kstrdup_const); * @s: the string to duplicate * @max: read at most @max chars from @s * @gfp: the GFP mask used in the kmalloc() call when allocating memory + * + * Note: Use kmemdup_nul() instead if the size is known exactly. */ char *kstrndup(const char *s, size_t max, gfp_t gfp) { @@ -121,6 +123,28 @@ void *kmemdup(const void *src, size_t len, gfp_t gfp) EXPORT_SYMBOL(kmemdup); /** + * kmemdup_nul - Create a NUL-terminated string from unterminated data + * @s: The data to stringify + * @len: The size of the data + * @gfp: the GFP mask used in the kmalloc() call when allocating memory + */ +char *kmemdup_nul(const char *s, size_t len, gfp_t gfp) +{ + char *buf; + + if (!s) + return NULL; + + buf = kmalloc_track_caller(len + 1, gfp); + if (buf) { + memcpy(buf, s, len); + buf[len] = '\0'; + } + return buf; +} +EXPORT_SYMBOL(kmemdup_nul); + +/** * memdup_user - duplicate memory region from user space * * @src: source address in user space