linux-kernel - Re: [PATCH]initialize the array of fs/ncpfs/inode.c

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Date:	Mon, 11 Apr 2011 16:18:38 -0700
From:	Andrew Morton <akpm@...ux-foundation.org>
To:	Harry Wei <jiaweiwei.xiyou@...il.com>
Cc:	petr@...drovec.name, viro@...iv.linux.org.uk, arnd@...db.de,
	npiggin@...nel.dk, jens.axboe@...cle.com, greg@...ah.com,
	joe@...ches.com, linux-kernel@...r.kernel.org
Subject: Re: [PATCH]initialize the array of fs/ncpfs/inode.c

On Sun, 10 Apr 2011 18:08:18 +0800
Harry Wei <jiaweiwei.xiyou@...il.com> wrote:

> Hi us,
> 	When i compile the linux-2.6.38.2, some warnings happened
> to me. One of them is like following.
> 
> fs/ncpfs/inode.c: In function 'ncp_fill_super':
> fs/ncpfs/inode.c:451: warning: 'data.mounted_vol[1u]' may be used 
> uninitialized in this function
> ...
> See details by the URL: 
> http://s1202.photobucket.com/albums/bb364/harrywei/Kernel/?action=view&current=patched.png

Yup.  The compiler is "wrong" because it doesn't know that the
uninitialised bytes will never be read, because they fall after the
'\0' in a null-terminated string.

> @@ -461,6 +462,7 @@ static int ncp_fill_super(struct super_block *sb, void *raw_data, int silent)
>  #endif
>  	struct ncp_entry_info finfo;
>  
> +	data.mounted_vol[NCP_VOLNAME_LEN + 1] = {0};
>  	data.wdog_pid = NULL;
>  	server = kzalloc(sizeof(struct ncp_server), GFP_KERNEL);
>  	if (!server)

hm.  I'm not sure that this fixed data.mounted_vol[2u],
data.mounted_vol[3u], etc.

How about we use the big hammer?



From: Andrew Morton <akpm@...ux-foundation.org>

fs/ncpfs/inode.c: In function 'ncp_fill_super':
fs/ncpfs/inode.c:451: warning: 'data.mounted_vol[1u]' may be used uninitialized in this function
fs/ncpfs/inode.c:451: warning: 'data.mounted_vol[2u]' may be used uninitialized in this function
fs/ncpfs/inode.c:451: warning: 'data.mounted_vol[3u]' may be used uninitialized in this function
...

It's notabug, but we can easily fix it with a memset().

Reported-by: Harry Wei <jiaweiwei.xiyou@...il.com>
Cc: Petr Vandrovec <petr@...drovec.name>
Signed-off-by: Andrew Morton <akpm@...ux-foundation.org>
---

 fs/ncpfs/inode.c |    4 +---
 1 file changed, 1 insertion(+), 3 deletions(-)

diff -puN fs/ncpfs/inode.c~fs-ncpfs-inodec-suppress-used-uninitialised-warning fs/ncpfs/inode.c
--- a/fs/ncpfs/inode.c~fs-ncpfs-inodec-suppress-used-uninitialised-warning
+++ a/fs/ncpfs/inode.c
@@ -461,7 +461,7 @@ static int ncp_fill_super(struct super_b
 #endif
 	struct ncp_entry_info finfo;
 
-	data.wdog_pid = NULL;
+	memset(data, 0, sizeof(data));
 	server = kzalloc(sizeof(struct ncp_server), GFP_KERNEL);
 	if (!server)
 		return -ENOMEM;
@@ -496,7 +496,6 @@ static int ncp_fill_super(struct super_b
 				struct ncp_mount_data_v4* md = (struct ncp_mount_data_v4*)raw_data;
 
 				data.flags = md->flags;
-				data.int_flags = 0;
 				data.mounted_uid = md->mounted_uid;
 				data.wdog_pid = find_get_pid(md->wdog_pid);
 				data.ncp_fd = md->ncp_fd;
@@ -507,7 +506,6 @@ static int ncp_fill_super(struct super_b
 				data.file_mode = md->file_mode;
 				data.dir_mode = md->dir_mode;
 				data.info_fd = -1;
-				data.mounted_vol[0] = 0;
 			}
 			break;
 		default:
_

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