linux-kernel - [RFC] 3.16-rc6 -- fs/direct-io.c:1011 from and to uninitialized.

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Date:	Tue, 22 Jul 2014 21:03:54 +0200
From:	Ian Kumlien <ian.kumlien@...il.com>
To:	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: [RFC] 3.16-rc6 -- fs/direct-io.c:1011 from and to uninitialized.

This is a resend, try two... 

---
Hi,

While playing around compiling the kernel i noticed the following:
fs/direct-io.c: In function ‘do_blockdev_direct_IO’:
fs/direct-io.c:1022:29: warning: ‘from’ may be used uninitialized in
this function [-Wmaybe-uninitialized]
    ret = submit_page_section(dio, sdio, page,
                             ^
fs/direct-io.c:913:10: note: ‘from’ was declared here
   size_t from, to;
          ^
fs/direct-io.c:1011:12: warning: ‘to’ may be used uninitialized in this
function [-Wmaybe-uninitialized]
    u = (to - from) >> blkbits;
            ^
fs/direct-io.c:913:16: note: ‘to’ was declared here
   size_t from, to;
                ^
---


And while the fix is simple, something along the lines of:
diff --git a/fs/direct-io.c b/fs/direct-io.c
index 98040ba..64a8286 100644
--- a/fs/direct-io.c
+++ b/fs/direct-io.c
@@ -910,7 +910,7 @@ static int do_direct_IO(struct dio *dio, struct
dio_submit *sdi
 
        while (sdio->block_in_file < sdio->final_block_in_request) {
                struct page *page;
-               size_t from, to;
+               size_t from, to = {0};
                page = dio_get_page(dio, sdio, &from, &to);
                if (IS_ERR(page)) {
                        ret = PTR_ERR(page);
---

I however don't know if it's in the correct C standard, it compiles fine
though... (or if this is more gcc speific)




View attachment "direct-io-init.patch" of type "text/x-patch" (1528 bytes)