Re: [External] [PATCH 5/6] cachefiles: Fix signed/unsigned mixup

From: Jia Zhu <zhujia.zj@bytedance.com>
To: David Howells <dhowells@redhat.com>,
	Christian Brauner <christian@brauner.io>,
	Jeff Layton <jlayton@kernel.org>,
	Gao Xiang <hsiangkao@linux.alibaba.com>,
	Dominique Martinet <asmadeus@codewreck.org>
Cc: Steve French <smfrench@gmail.com>,
	Matthew Wilcox <willy@infradead.org>,
	Marc Dionne <marc.dionne@auristor.com>,
	Paulo Alcantara <pc@manguebit.com>,
	Shyam Prasad N <sprasad@microsoft.com>,
	Tom Talpey <tom@talpey.com>,
	Eric Van Hensbergen <ericvh@kernel.org>,
	Ilya Dryomov <idryomov@gmail.com>,
	linux-cachefs@redhat.com, linux-afs@lists.infradead.org,
	linux-cifs@vger.kernel.org, linux-nfs@vger.kernel.org,
	ceph-devel@vger.kernel.org, v9fs@lists.linux.dev,
	linux-erofs@lists.ozlabs.org, linux-fsdevel@vger.kernel.org,
	linux-mm@kvack.org, netdev@vger.kernel.org,
	linux-kernel@vger.kernel.org, Simon Horman <horms@kernel.org>,
	kernel test robot <lkp@intel.com>,
	Yiqun Leng <yqleng@linux.alibaba.com>,
	zhujia.zj@bytedance.com
Subject: Re: [External] [PATCH 5/6] cachefiles: Fix signed/unsigned mixup
Date: Wed, 10 Jan 2024 20:05:50 +0800	[thread overview]
Message-ID: <abcc18ec-4006-4c51-96a8-e61d0ec2f092@bytedance.com> (raw)
In-Reply-To: <20240109112029.1572463-6-dhowells@redhat.com>

Tested-by: Jia Zhu <zhujia.zj@bytedance.com>

在 2024/1/9 19:20, David Howells 写道:
> In __cachefiles_prepare_write(), the start and pos variables were made
> unsigned 64-bit so that the casts in the checking could be got rid of -
> which should be fine since absolute file offsets can't be negative, except
> that an error code may be obtained from vfs_llseek(), which *would* be
> negative.  This breaks the error check.
> 
> Fix this for now by reverting pos and start to be signed and putting back
> the casts.  Unfortunately, the error value checks cannot be replaced with
> IS_ERR_VALUE() as long might be 32-bits.
> 
> Fixes: 7097c96411d2 ("cachefiles: Fix __cachefiles_prepare_write()")
> Reported-by: Simon Horman <horms@kernel.org>
> Reported-by: kernel test robot <lkp@intel.com>
> Closes: https://lore.kernel.org/oe-kbuild-all/202401071152.DbKqMQMu-lkp@intel.com/
> Signed-off-by: David Howells <dhowells@redhat.com>
> Reviewed-by: Simon Horman <horms@kernel.org>
> cc: Gao Xiang <hsiangkao@linux.alibaba.com>
> cc: Yiqun Leng <yqleng@linux.alibaba.com>
> cc: Jia Zhu <zhujia.zj@bytedance.com>
> cc: Jeff Layton <jlayton@kernel.org>
> cc: linux-cachefs@redhat.com
> cc: linux-erofs@lists.ozlabs.org
> cc: linux-fsdevel@vger.kernel.org
> cc: linux-mm@kvack.org
> ---
>   fs/cachefiles/io.c | 6 +++---
>   1 file changed, 3 insertions(+), 3 deletions(-)
> 
> diff --git a/fs/cachefiles/io.c b/fs/cachefiles/io.c
> index 3eec26967437..9a2cb2868e90 100644
> --- a/fs/cachefiles/io.c
> +++ b/fs/cachefiles/io.c
> @@ -522,7 +522,7 @@ int __cachefiles_prepare_write(struct cachefiles_object *object,
>   			       bool no_space_allocated_yet)
>   {
>   	struct cachefiles_cache *cache = object->volume->cache;
> -	unsigned long long start = *_start, pos;
> +	loff_t start = *_start, pos;
>   	size_t len = *_len;
>   	int ret;
>   
> @@ -556,7 +556,7 @@ int __cachefiles_prepare_write(struct cachefiles_object *object,
>   					  cachefiles_trace_seek_error);
>   		return pos;
>   	}
> -	if (pos >= start + *_len)
> +	if ((u64)pos >= (u64)start + *_len)
>   		goto check_space; /* Unallocated region */
>   
>   	/* We have a block that's at least partially filled - if we're low on
> @@ -575,7 +575,7 @@ int __cachefiles_prepare_write(struct cachefiles_object *object,
>   					  cachefiles_trace_seek_error);
>   		return pos;
>   	}
> -	if (pos >= start + *_len)
> +	if ((u64)pos >= (u64)start + *_len)
>   		return 0; /* Fully allocated */
>   
>   	/* Partially allocated, but insufficient space: cull. */
>