From 9cad27a3dc1a4eb349b6591e4dc8cc89dce32277 Mon Sep 17 00:00:00 2001 From: Rich Felker Date: Fri, 13 Jul 2018 21:56:27 -0400 Subject: [PATCH] fix writes outside buffer by ungetc after setvbuf commit 0b80a7b0404b6e49b0b724e3e3fe0ed5af3b08ef, which added non-stub setvbuf, applied the UNGET pushback adjustment to the size of the buffer passed in, but inadvertently omitted offsetting the start by the same amount, thereby allowing unget to clobber up to 8 bytes before the start of the buffer. this bug was introduced in the present release cycle; no releases are affected. --- src/stdio/setvbuf.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/src/stdio/setvbuf.c b/src/stdio/setvbuf.c index b6b9b018..06ea296c 100644 --- a/src/stdio/setvbuf.c +++ b/src/stdio/setvbuf.c @@ -14,7 +14,7 @@ int setvbuf(FILE *restrict f, char *restrict buf, int type, size_t size) f->buf_size = 0; } else { if (buf && size >= UNGET) { - f->buf = (void *)buf; + f->buf = (void *)(buf + UNGET); f->buf_size = size - UNGET; } if (type == _IOLBF && f->buf_size) -- 2.25.1