linux-kernel - Re: [patch] vfs: check for integer overflows in posix_acl

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Message-ID: <20130624164329.GG5714@mwanda>
Date:	Mon, 24 Jun 2013 19:43:29 +0300
From:	Dan Carpenter <dan.carpenter@...cle.com>
To:	Alexander Viro <viro@...iv.linux.org.uk>
Cc:	linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [patch] vfs: check for integer overflows in posix_acl_alloc()

On Mon, Jun 24, 2013 at 07:27:19PM +0300, Dan Carpenter wrote:
> We've seen cases where people passed negative numbers to
> posix_acl_alloc() and we fixed the caller.  For example 093019cf1b "xfs:
> fix acl count validation in xfs_acl_from_disk()".  But there are other
> places which might be affected like ext4_acl_from_disk() which checks
> for negative but doesn't check an upper limit.
> 
> Signed-off-by: Dan Carpenter <dan.carpenter@...cle.com>
> 
> diff --git a/fs/posix_acl.c b/fs/posix_acl.c
> index cea4623..cd7fd2f 100644
> --- a/fs/posix_acl.c
> +++ b/fs/posix_acl.c
> @@ -46,7 +46,12 @@ posix_acl_alloc(int count, gfp_t flags)
>  {
>  	const size_t size = sizeof(struct posix_acl) +
>  	                    count * sizeof(struct posix_acl_entry);
> -	struct posix_acl *acl = kmalloc(size, flags);
> +	struct posix_acl *acl;
> +
> +	if (count < 0 || count > (SIZE_MAX - sizeof(struct posix_acl) /
> +					sizeof(struct posix_acl_entry)))

Gar.  I completely screwed that up.  Please ignore this.  I will
send a better patch in a couple days.  I am sorry.

regards,
dan carpenter

> +		return NULL;
> +	acl = kmalloc(size, flags);
>  	if (acl)
>  		posix_acl_init(acl, count);
>  	return acl;
--
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