On 8/7/2014 2:43 AM, Randy Dunlap wrote:
On 08/06/14 11:16, Chris Metcalf wrote:
Using strncpy() will just silently truncate long strings; we should
instead return an appropriate error. Using strlcpy() would suffer from
the same problem. Instead, use strnlen()+memcpy(), and add an
error-checking step to make sure the lengths are reasonable.
I called the convenience wrapper strscpy(), and a case could be made for
making it more generic (possibly with a better name), but that seems
outside the scope of this initial commit.
Well, having looked at the function before I read this comment, my first
thought was that it should be added to lib/string.c for general
availability.
I'm happy to do that, but it probably shouldn't go through the linux-tile
tree in that case, since I'd be touching platform-independent code.
If someone wants to volunteer to push a new lib/strscpy.c change to Linus
(presumably including the arch/tile caller) I'm happy to redo this commit
in that form.
My guess is that we also haven't hit the mandatory minimum of
bike-shedding around function name and precise semantics yet, anyway :-)
I will hold off on pushing this change until a bit later in the merge
window to see if anyone wants to jump in.
diff --git a/arch/tile/gxio/mpipe.c b/arch/tile/gxio/mpipe.c
index 5301a9ffbae1..27a56be8d583 100644
--- a/arch/tile/gxio/mpipe.c
+++ b/arch/tile/gxio/mpipe.c
@@ -29,6 +29,25 @@
/* HACK: Avoid pointless "shadow" warnings. */
#define link link_shadow
+/*
+ * Use this routine to avoid copying too-long strings. Unlike strncpy
+ * or strlcpy, we don't enable programmers who don't check return codes;
+ * partially-copied strings can be problematic. The routine returns
+ * the total number of bytes copied (including the trailing NUL) or
+ * zero if the buffer wasn't big enough.
+ */
+static size_t strscpy(char *dest, const char *src, size_t size)
+{
+ size_t ret = strnlen(src, size) + 1;
+ if (ret > size) {
+ if (size)
+ dest[0] = '\0';
+ return 0;
+ }
+ memcpy(dest, src, ret);
+ return ret;
+}
--
Chris Metcalf, Tilera Corp.
http://www.tilera.com
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