vsprintf: make %pV handling compatible with kasprintf()

kasprintf() (and potentially other functions that I didn't run across so
far) want to evaluate argument lists twice.  Caring to do so for the
primary list is obviously their job, but they can't reasonably be
expected to check the format string for instances of %pV, which however
need special handling too: On architectures like x86-64 (as opposed to
e.g.  ix86), using the same argument list twice doesn't produce the
expected results, as an internally managed cursor gets updated during
the first run.

Fix the problem by always acting on a copy of the original list when
handling %pV.

Signed-off-by: Jan Beulich <jbeulich@suse.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/lib/vsprintf.c b/lib/vsprintf.c
index 8e75003d62f632c52b8c0ea56ca62bdc72e560f0..38e612e66da5993f7b1eb92065ebfec45216d83c 100644 (file)
--- a/lib/vsprintf.c
+++ b/lib/vsprintf.c
@@ -891,9 +891,15 @@ char *pointer(const char *fmt, char *buf, char *end, void *ptr,
        case 'U':
                return uuid_string(buf, end, ptr, spec, fmt);
        case 'V':
-               return buf + vsnprintf(buf, end > buf ? end - buf : 0,
-                                      ((struct va_format *)ptr)->fmt,
-                                      *(((struct va_format *)ptr)->va));
+               {
+                       va_list va;
+
+                       va_copy(va, *((struct va_format *)ptr)->va);
+                       buf += vsnprintf(buf, end > buf ? end - buf : 0,
+                                        ((struct va_format *)ptr)->fmt, va);
+                       va_end(va);
+                       return buf;
+               }
        case 'K':
                /*
                 * %pK cannot be used in IRQ context because its test