[PATCH 3.16 310/370] lib/vsprintf.c: improve sanity check in vsnprintf()

Ben Hutchings
2017-03-10T13:33:17Z

From: Rasmus Villemoes <linux@rasmusvillemoes.dk>

commit 2aa2f9e21e4eb25c720b2e7d80f8929638f6ad73 upstream.

On 64 bit, size may very well be huge even if bit 31 happens to be 0.
Somehow it doesn't feel right that one can pass a 5 GiB buffer but not a
3 GiB one. So cap at INT_MAX as was probably the intention all along.
This is also the made-up value passed by sprintf and vsprintf.

Signed-off-by: Rasmus Villemoes <linux@rasmusvillemoes.dk>
Cc: Jiri Kosina <jkosina@suse.cz>
Cc: Randy Dunlap <rdunlap@infradead.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
Cc: Willy Tarreau <w@1wt.eu>
---
lib/vsprintf.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

--- a/lib/vsprintf.c
+++ b/lib/vsprintf.c
@@ -1657,7 +1657,7 @@ int vsnprintf(char *buf, size_t size, co

/* Reject out-of-range values early. Large positive sizes are
used for unknown buffer sizes. */
- if (WARN_ON_ONCE((int) size < 0))
+ if (WARN_ON_ONCE(size > INT_MAX))
return 0;

str = buf;