Re: [PATCH] btrfs: fix extent buffer read/write range checks

[Nikolay Borisov <nborisov@suse.com>]

On 26.07.19 г. 8:27 ч., Naohiro Aota wrote:
> Several functions to read/write an extent buffer check if specified offset
> range resides in the size of the extent buffer. However, those checks have
> two problems:
> 
> (1) they don't catch "start == eb->len" case.
> (2) it checks offset in extent buffer against logical address using
>     eb->start.
> 
> Generally, eb->start is much larger than the offset, so the second WARN_ON
> was almost useless.
> 
> Fix these problems in read_extent_buffer_to_user(),
> {memcmp,write,memzero}_extent_buffer().
> 
> Signed-off-by: Naohiro Aota <naohiro.aota@wdc.com>

Qu already sent similar patch:

[PATCH v2 1/5] btrfs: extent_io: Do extra check for extent buffer read
write functions


He centralised the checking code, your >= fixes though should be merged
there.


> ---
>  fs/btrfs/extent_io.c | 16 ++++++++--------
>  1 file changed, 8 insertions(+), 8 deletions(-)
> 
> diff --git a/fs/btrfs/extent_io.c b/fs/btrfs/extent_io.c
> index 50cbaf1dad5b..c0174f530568 100644
> --- a/fs/btrfs/extent_io.c
> +++ b/fs/btrfs/extent_io.c
> @@ -5545,8 +5545,8 @@ int read_extent_buffer_to_user(const struct extent_buffer *eb,
>  	unsigned long i = (start_offset + start) >> PAGE_SHIFT;
>  	int ret = 0;
>  
> -	WARN_ON(start > eb->len);
> -	WARN_ON(start + len > eb->start + eb->len);
> +	WARN_ON(start >= eb->len);
> +	WARN_ON(start + len > eb->len);
>  
>  	offset = offset_in_page(start_offset + start);
>  
> @@ -5623,8 +5623,8 @@ int memcmp_extent_buffer(const struct extent_buffer *eb, const void *ptrv,
>  	unsigned long i = (start_offset + start) >> PAGE_SHIFT;
>  	int ret = 0;
>  
> -	WARN_ON(start > eb->len);
> -	WARN_ON(start + len > eb->start + eb->len);
> +	WARN_ON(start >= eb->len);
> +	WARN_ON(start + len > eb->len);
>  
>  	offset = offset_in_page(start_offset + start);
>  
> @@ -5678,8 +5678,8 @@ void write_extent_buffer(struct extent_buffer *eb, const void *srcv,
>  	size_t start_offset = offset_in_page(eb->start);
>  	unsigned long i = (start_offset + start) >> PAGE_SHIFT;
>  
> -	WARN_ON(start > eb->len);
> -	WARN_ON(start + len > eb->start + eb->len);
> +	WARN_ON(start >= eb->len);
> +	WARN_ON(start + len > eb->len);
>  
>  	offset = offset_in_page(start_offset + start);
>  
> @@ -5708,8 +5708,8 @@ void memzero_extent_buffer(struct extent_buffer *eb, unsigned long start,
>  	size_t start_offset = offset_in_page(eb->start);
>  	unsigned long i = (start_offset + start) >> PAGE_SHIFT;
>  
> -	WARN_ON(start > eb->len);
> -	WARN_ON(start + len > eb->start + eb->len);
> +	WARN_ON(start >= eb->len);
> +	WARN_ON(start + len > eb->len);
>  
>  	offset = offset_in_page(start_offset + start);
>  
>