From 8e2a2bfdb86ecb2421e3dd18d0fbbb42f2d943ad Mon Sep 17 00:00:00 2001 From: Rasmus Villemoes Date: Fri, 15 Jan 2016 16:58:47 -0800 Subject: [PATCH] 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: Rasmus Villemoes Cc: Al Viro Cc: Andy Shevchenko Cc: Ingo Molnar Cc: Joe Perches Cc: Kees Cook Cc: Maurizio Lombardi Cc: Tejun Heo Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- lib/kasprintf.c | 10 ++++++---- 1 file changed, 6 insertions(+), 4 deletions(-) diff --git a/lib/kasprintf.c b/lib/kasprintf.c index f194e6e593e1..7f6c506a4942 100644 --- a/lib/kasprintf.c +++ b/lib/kasprintf.c @@ -13,19 +13,21 @@ /* Simplified asprintf. */ char *kvasprintf(gfp_t gfp, const char *fmt, va_list ap) { - unsigned int len; + unsigned int first, second; char *p; va_list aq; va_copy(aq, ap); - len = vsnprintf(NULL, 0, fmt, aq); + first = vsnprintf(NULL, 0, fmt, aq); va_end(aq); - p = kmalloc_track_caller(len+1, gfp); + p = kmalloc_track_caller(first+1, gfp); if (!p) 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; } -- 2.30.2