[PATCH] kbuild: fix buffer overflow in modpost

Jiri Benc <jbenc@suse.cz> reported that modpost would stop with SIGABRT if
used with long filepaths.
The error looked like:
>   Building modules, stage 2.
>   MODPOST
> *** glibc detected *** scripts/mod/modpost: realloc(): invalid next size:
+0x0809f588 ***
> [...]

Fix this by allocating at least the required memory + SZ bytes each time.
Before we sometimes ended up allocating too little memory resuting in the
glibc detected bug above.  Based on patch originally submitted by: Jiri
Benc <jbenc@suse.cz>

Signed-off-by: Sam Ravnborg <sam@ravnborg.org>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

1 files changed, 2 insertions, 7 deletions

diff --git a/scripts/mod/modpost.c b/scripts/mod/modpost.c
index f70ff13d4818..b8b2a560b26b 100644
--- a/scripts/mod/modpost.c
+++ b/scripts/mod/modpost.c
@@ -508,12 +508,7 @@ buf_printf(struct buffer *buf, const char *fmt, ...)
         
         va_start(ap, fmt);
         len = vsnprintf(tmp, SZ, fmt, ap);
-        if (buf->size - buf->pos < len + 1) {
-                buf->size += 128;
-                buf->p = realloc(buf->p, buf->size);
-        }
-        strncpy(buf->p + buf->pos, tmp, len + 1);
-        buf->pos += len;
+        buf_write(buf, tmp, len);
         va_end(ap);
 }
 
@@ -521,7 +516,7 @@ void
 buf_write(struct buffer *buf, const char *s, int len)
 {
         if (buf->size - buf->pos < len) {
-                buf->size += len;
+                buf->size += len + SZ;
                 buf->p = realloc(buf->p, buf->size);
         }
         strncpy(buf->p + buf->pos, s, len);