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

[Jia Zhu]

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

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@xxxxxxxxxx>
> Reported-by: kernel test robot <lkp@xxxxxxxxx>
> Closes: https://lore.kernel.org/oe-kbuild-all/202401071152.DbKqMQMu-lkp@xxxxxxxxx/
> Signed-off-by: David Howells <dhowells@xxxxxxxxxx>
> Reviewed-by: Simon Horman <horms@xxxxxxxxxx>
> cc: Gao Xiang <hsiangkao@xxxxxxxxxxxxxxxxx>
> cc: Yiqun Leng <yqleng@xxxxxxxxxxxxxxxxx>
> cc: Jia Zhu <zhujia.zj@xxxxxxxxxxxxx>
> cc: Jeff Layton <jlayton@xxxxxxxxxx>
> cc: linux-cachefs@xxxxxxxxxx
> cc: linux-erofs@xxxxxxxxxxxxxxxx
> cc: linux-fsdevel@xxxxxxxxxxxxxxx
> cc: linux-mm@xxxxxxxxx
> ---
>   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. */