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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>
This commit is contained in:
Rasmus Villemoes 2016-01-15 16:58:47 -08:00 committed by Linus Torvalds
parent 4d72ba014b
commit 8e2a2bfdb8
1 changed files with 6 additions and 4 deletions
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10
lib/kasprintf.c
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@ -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;
}