[-next] btrfs: Fix type conversion in btrfs_read_root_item
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Message ID 20190220030840.188854-1-yuehaibing@huawei.com
State New
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  • [-next] btrfs: Fix type conversion in btrfs_read_root_item
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Yuehaibing Feb. 20, 2019, 3:08 a.m. UTC
btrfs_item_size_nr return value is u32, convert it to int may result
in truncation.Also read_extent_buffer expect a unsigned param, so
min_t should use type u32 to compare.

Fixes: 8ea05e3a4262 ("Btrfs: introduce subvol uuids and times")
Signed-off-by: YueHaibing <yuehaibing@huawei.com>
---
 fs/btrfs/root-tree.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

Comments

Qu Wenruo Feb. 20, 2019, 3:38 a.m. UTC | #1
On 2019/2/20 上午11:08, YueHaibing wrote:
> btrfs_item_size_nr return value is u32, convert it to int may result
> in truncation.Also read_extent_buffer expect a unsigned param, so
> min_t should use type u32 to compare.

Btrfs has a up limit on item size, it will never exceed 64K - various
overhead.

Furthermore, btrfs has metadata read time check to exclude such
obviously corrupted tree blocks, thus corrupted tree block will never
reach here.

Thanks,
Qu

> 
> Fixes: 8ea05e3a4262 ("Btrfs: introduce subvol uuids and times")
> Signed-off-by: YueHaibing <yuehaibing@huawei.com>
> ---
>  fs/btrfs/root-tree.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/fs/btrfs/root-tree.c b/fs/btrfs/root-tree.c
> index 02d1a57af78b..893d12fbfda0 100644
> --- a/fs/btrfs/root-tree.c
> +++ b/fs/btrfs/root-tree.c
> @@ -21,12 +21,12 @@ static void btrfs_read_root_item(struct extent_buffer *eb, int slot,
>  				struct btrfs_root_item *item)
>  {
>  	uuid_le uuid;
> -	int len;
> +	u32 len;
>  	int need_reset = 0;
>  
>  	len = btrfs_item_size_nr(eb, slot);
>  	read_extent_buffer(eb, item, btrfs_item_ptr_offset(eb, slot),
> -			min_t(int, len, (int)sizeof(*item)));
> +			   min_t(u32, len, sizeof(*item)));
>  	if (len < sizeof(*item))
>  		need_reset = 1;
>  	if (!need_reset && btrfs_root_generation(item)
> 
> 
>
Dan Carpenter Feb. 20, 2019, 5:58 a.m. UTC | #2
On Wed, Feb 20, 2019 at 03:08:40AM +0000, YueHaibing wrote:
> btrfs_item_size_nr return value is u32, convert it to int may result
> in truncation.Also read_extent_buffer expect a unsigned param, so
> min_t should use type u32 to compare.
> 
> Fixes: 8ea05e3a4262 ("Btrfs: introduce subvol uuids and times")
> Signed-off-by: YueHaibing <yuehaibing@huawei.com>
> ---
>  fs/btrfs/root-tree.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/fs/btrfs/root-tree.c b/fs/btrfs/root-tree.c
> index 02d1a57af78b..893d12fbfda0 100644
> --- a/fs/btrfs/root-tree.c
> +++ b/fs/btrfs/root-tree.c
> @@ -21,12 +21,12 @@ static void btrfs_read_root_item(struct extent_buffer *eb, int slot,
>  				struct btrfs_root_item *item)
>  {
>  	uuid_le uuid;
> -	int len;
> +	u32 len;
>  	int need_reset = 0;
>  
>  	len = btrfs_item_size_nr(eb, slot);
>  	read_extent_buffer(eb, item, btrfs_item_ptr_offset(eb, slot),
> -			min_t(int, len, (int)sizeof(*item)));
                              ^^^^^^^^^^^^^^^^^^^^^^^^^^^^
Yeah, min_t() should normally cast to unsigned and the extra cast is
silly.

> +			   min_t(u32, len, sizeof(*item)));

regards,
dan carpenter
Dan Carpenter Feb. 20, 2019, 6:10 a.m. UTC | #3
On Wed, Feb 20, 2019 at 08:58:43AM +0300, Dan Carpenter wrote:
> On Wed, Feb 20, 2019 at 03:08:40AM +0000, YueHaibing wrote:
> > btrfs_item_size_nr return value is u32, convert it to int may result
> > in truncation.Also read_extent_buffer expect a unsigned param, so
> > min_t should use type u32 to compare.
> > 
> > Fixes: 8ea05e3a4262 ("Btrfs: introduce subvol uuids and times")
> > Signed-off-by: YueHaibing <yuehaibing@huawei.com>
> > ---
> >  fs/btrfs/root-tree.c | 4 ++--
> >  1 file changed, 2 insertions(+), 2 deletions(-)
> > 
> > diff --git a/fs/btrfs/root-tree.c b/fs/btrfs/root-tree.c
> > index 02d1a57af78b..893d12fbfda0 100644
> > --- a/fs/btrfs/root-tree.c
> > +++ b/fs/btrfs/root-tree.c
> > @@ -21,12 +21,12 @@ static void btrfs_read_root_item(struct extent_buffer *eb, int slot,
> >  				struct btrfs_root_item *item)
> >  {
> >  	uuid_le uuid;
> > -	int len;
> > +	u32 len;
> >  	int need_reset = 0;
> >  
> >  	len = btrfs_item_size_nr(eb, slot);
> >  	read_extent_buffer(eb, item, btrfs_item_ptr_offset(eb, slot),
> > -			min_t(int, len, (int)sizeof(*item)));
>                               ^^^^^^^^^^^^^^^^^^^^^^^^^^^^
> Yeah, min_t() should normally cast to unsigned and the extra cast is
> silly.
> 

Btw, I shouldn't have had to dig through the patch to find the *real*
reason you wrote it.  A better description would have said:

    There is a messy cast here:

	min_t(int, len, (int)sizeof(*item)));

    min_t() should normally cast to unsigned.  It's not possible for
    "len" to be negative, but if it were then then we definitely
    wouldn't want to pass negatives to read_extent_buffer().  Also there
    is an extra cast.

    This patch shouldn't affect runtime, it's just a clean up.

regards,
dan carpenter
Yuehaibing Feb. 20, 2019, 9:10 a.m. UTC | #4
On 2019/2/20 14:10, Dan Carpenter wrote:
> On Wed, Feb 20, 2019 at 08:58:43AM +0300, Dan Carpenter wrote:
>> On Wed, Feb 20, 2019 at 03:08:40AM +0000, YueHaibing wrote:
>>> btrfs_item_size_nr return value is u32, convert it to int may result
>>> in truncation.Also read_extent_buffer expect a unsigned param, so
>>> min_t should use type u32 to compare.
>>>
>>> Fixes: 8ea05e3a4262 ("Btrfs: introduce subvol uuids and times")
>>> Signed-off-by: YueHaibing <yuehaibing@huawei.com>
>>> ---
>>>  fs/btrfs/root-tree.c | 4 ++--
>>>  1 file changed, 2 insertions(+), 2 deletions(-)
>>>
>>> diff --git a/fs/btrfs/root-tree.c b/fs/btrfs/root-tree.c
>>> index 02d1a57af78b..893d12fbfda0 100644
>>> --- a/fs/btrfs/root-tree.c
>>> +++ b/fs/btrfs/root-tree.c
>>> @@ -21,12 +21,12 @@ static void btrfs_read_root_item(struct extent_buffer *eb, int slot,
>>>  				struct btrfs_root_item *item)
>>>  {
>>>  	uuid_le uuid;
>>> -	int len;
>>> +	u32 len;
>>>  	int need_reset = 0;
>>>  
>>>  	len = btrfs_item_size_nr(eb, slot);
>>>  	read_extent_buffer(eb, item, btrfs_item_ptr_offset(eb, slot),
>>> -			min_t(int, len, (int)sizeof(*item)));
>>                               ^^^^^^^^^^^^^^^^^^^^^^^^^^^^
>> Yeah, min_t() should normally cast to unsigned and the extra cast is
>> silly.
>>
> 
> Btw, I shouldn't have had to dig through the patch to find the *real*
> reason you wrote it.  A better description would have said:
> 
>     There is a messy cast here:
> 
> 	min_t(int, len, (int)sizeof(*item)));
> 
>     min_t() should normally cast to unsigned.  It's not possible for
>     "len" to be negative, but if it were then then we definitely
>     wouldn't want to pass negatives to read_extent_buffer().  Also there
>     is an extra cast.
> 
>     This patch shouldn't affect runtime, it's just a clean up.

Yes, This just a cleanup, Thanks!

> 
> regards,
> dan carpenter
> 
> 
> .
>

Patch
diff mbox series

diff --git a/fs/btrfs/root-tree.c b/fs/btrfs/root-tree.c
index 02d1a57af78b..893d12fbfda0 100644
--- a/fs/btrfs/root-tree.c
+++ b/fs/btrfs/root-tree.c
@@ -21,12 +21,12 @@  static void btrfs_read_root_item(struct extent_buffer *eb, int slot,
 				struct btrfs_root_item *item)
 {
 	uuid_le uuid;
-	int len;
+	u32 len;
 	int need_reset = 0;
 
 	len = btrfs_item_size_nr(eb, slot);
 	read_extent_buffer(eb, item, btrfs_item_ptr_offset(eb, slot),
-			min_t(int, len, (int)sizeof(*item)));
+			   min_t(u32, len, sizeof(*item)));
 	if (len < sizeof(*item))
 		need_reset = 1;
 	if (!need_reset && btrfs_root_generation(item)