Commit 8e2a2bfd authored by Rasmus Villemoes's avatar Rasmus Villemoes Committed by Linus Torvalds

lib/kasprintf.c: add sanity check to kvasprintf

kasprintf relies on being able to replay the formatting and getting the
same result (in particular, the same length).  This will almost always
work, but it is possible that the object pointed to by a %s or %p
argument changed under us (so we might get truncated output).  Add a
somewhat paranoid sanity check and let's see if it ever triggers.
Signed-off-by: default avatarRasmus Villemoes <linux@rasmusvillemoes.dk>
Cc: Al Viro <viro@ZenIV.linux.org.uk>
Cc: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Joe Perches <joe@perches.com>
Cc: Kees Cook <keescook@chromium.org>
Cc: Maurizio Lombardi <mlombard@redhat.com>
Cc: Tejun Heo <tj@kernel.org>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 4d72ba01
...@@ -13,19 +13,21 @@ ...@@ -13,19 +13,21 @@
/* Simplified asprintf. */ /* Simplified asprintf. */
char *kvasprintf(gfp_t gfp, const char *fmt, va_list ap) char *kvasprintf(gfp_t gfp, const char *fmt, va_list ap)
{ {
unsigned int len; unsigned int first, second;
char *p; char *p;
va_list aq; va_list aq;
va_copy(aq, ap); va_copy(aq, ap);
len = vsnprintf(NULL, 0, fmt, aq); first = vsnprintf(NULL, 0, fmt, aq);
va_end(aq); va_end(aq);
p = kmalloc_track_caller(len+1, gfp); p = kmalloc_track_caller(first+1, gfp);
if (!p) if (!p)
return NULL; return NULL;
vsnprintf(p, len+1, fmt, ap); second = vsnprintf(p, first+1, fmt, ap);
WARN(first != second, "different return values (%u and %u) from vsnprintf(\"%s\", ...)",
first, second, fmt);
return p; return p;
} }
......
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