Re: [PATCH] lib/vsprintf.c: fix the incorrect return value of vsnprintf()

["George Spelvin" <linux@horizon.com>]

> When "str >= end", necessary to reset 'str' to "end - 1", or the return
> value will be larger than the real one, the callers which depend on the
> return value, may cause memory overflow.

NAK.  This is the documented (by both the function itself and the
ANSI/ISO C standard) and desired return value: the number of bytes that
*would* have been in the output string if the buffer were large enough.
In particular, it is common to do:

size = vsnprintf(NULL, 0, fmt, args) + 1;
p = malloc(size, GFP_KERNEL);
vsnprintf(p, size, fmt, args);

You want vscnprintf.  If you have a caller that needs the *actual* number of
bytes written, use that.