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

Naohiro Aota
2019-07-26T06:13:04Z

On Fri, Jul 26, 2019 at 08:38:27AM +0300, Nikolay Borisov wrote:
>
>
>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.

Oops, I missed that series. Thank you for pointing out. Then, this
should be merged into Qu's version.

Qu, could you pick the change from "start > eb->len" to "start >= eb->len"?

>
>
>> ---
>> 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);
>>
>>