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authorRasmus Villemoes <linux@rasmusvillemoes.dk>2016-01-15 16:58:47 -0800
committerLinus Torvalds <torvalds@linux-foundation.org>2016-01-16 11:17:27 -0800
commit8e2a2bfdb86ecb2421e3dd18d0fbbb42f2d943ad (patch)
tree5b5ed17a7234ad1bba7be081f533700de1a5736d
parent4d72ba014b4b0913f448ccaaaa2e8b39c54e3738 (diff)
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 <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: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
-rw-r--r--lib/kasprintf.c10
1 files 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;
}