* Btrfs: check range early in map_private_extent_buffer
@ 2012-09-24 4:38 Wang Sheng-Hui
2012-09-24 16:17 ` David Sterba
0 siblings, 1 reply; 3+ messages in thread
From: Wang Sheng-Hui @ 2012-09-24 4:38 UTC (permalink / raw)
To: chris.mason, jbacik, linux-btrfs, linux-kernel
Check range early to avoid further check/compute in case
of range error.
Signed-off-by: Wang Sheng-Hui <shhuiw@gmail.com>
---
fs/btrfs/extent_io.c | 16 ++++++++--------
1 files changed, 8 insertions(+), 8 deletions(-)
diff --git a/fs/btrfs/extent_io.c b/fs/btrfs/extent_io.c
index 4c87847..9250cf5 100644
--- a/fs/btrfs/extent_io.c
+++ b/fs/btrfs/extent_io.c
@@ -4643,6 +4643,14 @@ int map_private_extent_buffer(struct extent_buffer *eb, unsigned long start,
unsigned long end_i = (start_offset + start + min_len - 1) >>
PAGE_CACHE_SHIFT;
+ if (start + min_len > eb->len) {
+ printk(KERN_ERR "btrfs bad mapping eb start %llu len %lu, "
+ "wanted %lu %lu\n", (unsigned long long)eb->start,
+ eb->len, start, min_len);
+ WARN_ON(1);
+ return -EINVAL;
+ }
+
if (i != end_i)
return -EINVAL;
@@ -4654,14 +4662,6 @@ int map_private_extent_buffer(struct extent_buffer *eb, unsigned long start,
*map_start = ((u64)i << PAGE_CACHE_SHIFT) - start_offset;
}
- if (start + min_len > eb->len) {
- printk(KERN_ERR "btrfs bad mapping eb start %llu len %lu, "
- "wanted %lu %lu\n", (unsigned long long)eb->start,
- eb->len, start, min_len);
- WARN_ON(1);
- return -EINVAL;
- }
-
p = extent_buffer_page(eb, i);
kaddr = page_address(p);
*map = kaddr + offset;
--
1.7.1
^ permalink raw reply related [flat|nested] 3+ messages in thread
* Re: Btrfs: check range early in map_private_extent_buffer
2012-09-24 4:38 Btrfs: check range early in map_private_extent_buffer Wang Sheng-Hui
@ 2012-09-24 16:17 ` David Sterba
2012-09-25 0:24 ` Wang Sheng-Hui
0 siblings, 1 reply; 3+ messages in thread
From: David Sterba @ 2012-09-24 16:17 UTC (permalink / raw)
To: Wang Sheng-Hui; +Cc: chris.mason, jbacik, linux-btrfs, linux-kernel
On Mon, Sep 24, 2012 at 12:38:07PM +0800, Wang Sheng-Hui wrote:
> Check range early to avoid further check/compute in case
> of range error.
>
> Signed-off-by: Wang Sheng-Hui <shhuiw@gmail.com>
> ---
> fs/btrfs/extent_io.c | 16 ++++++++--------
> 1 files changed, 8 insertions(+), 8 deletions(-)
>
> diff --git a/fs/btrfs/extent_io.c b/fs/btrfs/extent_io.c
> index 4c87847..9250cf5 100644
> --- a/fs/btrfs/extent_io.c
> +++ b/fs/btrfs/extent_io.c
> @@ -4643,6 +4643,14 @@ int map_private_extent_buffer(struct extent_buffer *eb, unsigned long start,
> unsigned long end_i = (start_offset + start + min_len - 1) >>
> PAGE_CACHE_SHIFT;
>
> + if (start + min_len > eb->len) {
> + printk(KERN_ERR "btrfs bad mapping eb start %llu len %lu, "
> + "wanted %lu %lu\n", (unsigned long long)eb->start,
> + eb->len, start, min_len);
> + WARN_ON(1);
> + return -EINVAL;
> + }
> +
> if (i != end_i)
> return -EINVAL;
4665 unsigned long i = (start_offset + start) >> PAGE_CACHE_SHIFT;
4666 unsigned long end_i = (start_offset + start + min_len - 1) >>
4667 PAGE_CACHE_SHIFT;
so the check above effectively verifies that
min_len - 1 < PAGE_CACHE_SIZE
AND
is within the same page
The other check
if (start + min_len > eb->len) {
looks if the requested data do not lie out of the bounds of the extent
buffer, where min_len is filled with sizeof(something).
So, both the checks look for corrupted metadata, I don't see the need to
swap them.
david
^ permalink raw reply [flat|nested] 3+ messages in thread
* Re: Btrfs: check range early in map_private_extent_buffer
2012-09-24 16:17 ` David Sterba
@ 2012-09-25 0:24 ` Wang Sheng-Hui
0 siblings, 0 replies; 3+ messages in thread
From: Wang Sheng-Hui @ 2012-09-25 0:24 UTC (permalink / raw)
To: chris.mason, jbacik, linux-btrfs, linux-kernel
On 2012年09月25日 00:17, David Sterba wrote:
> On Mon, Sep 24, 2012 at 12:38:07PM +0800, Wang Sheng-Hui wrote:
>> Check range early to avoid further check/compute in case
>> of range error.
>>
>> Signed-off-by: Wang Sheng-Hui <shhuiw@gmail.com>
>> ---
>> fs/btrfs/extent_io.c | 16 ++++++++--------
>> 1 files changed, 8 insertions(+), 8 deletions(-)
>>
>> diff --git a/fs/btrfs/extent_io.c b/fs/btrfs/extent_io.c
>> index 4c87847..9250cf5 100644
>> --- a/fs/btrfs/extent_io.c
>> +++ b/fs/btrfs/extent_io.c
>> @@ -4643,6 +4643,14 @@ int map_private_extent_buffer(struct extent_buffer *eb, unsigned long start,
>> unsigned long end_i = (start_offset + start + min_len - 1) >>
>> PAGE_CACHE_SHIFT;
>>
>> + if (start + min_len > eb->len) {
>> + printk(KERN_ERR "btrfs bad mapping eb start %llu len %lu, "
>> + "wanted %lu %lu\n", (unsigned long long)eb->start,
>> + eb->len, start, min_len);
>> + WARN_ON(1);
>> + return -EINVAL;
>> + }
>> +
>> if (i != end_i)
>> return -EINVAL;
>
> 4665 unsigned long i = (start_offset + start) >> PAGE_CACHE_SHIFT;
> 4666 unsigned long end_i = (start_offset + start + min_len - 1) >>
> 4667 PAGE_CACHE_SHIFT;
>
> so the check above effectively verifies that
>
> min_len - 1 < PAGE_CACHE_SIZE
> AND
> is within the same page
>
> The other check
>
> if (start + min_len > eb->len) {
>
> looks if the requested data do not lie out of the bounds of the extent
> buffer, where min_len is filled with sizeof(something).
>
> So, both the checks look for corrupted metadata, I don't see the need to
> swap them.
Reread the code and it really does the check.
Got it. Thanks for your explanation.
>
> david
^ permalink raw reply [flat|nested] 3+ messages in thread
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2012-09-24 16:17 ` David Sterba
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