Re: [PATCH -next] btrfs: Fix type conversion in btrfs_read_root_item
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 +, 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
>>> ---
>>> 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
>
>
> .
>
Re: [PATCH -next] btrfs: Fix type conversion in btrfs_read_root_item
On Wed, Feb 20, 2019 at 08:58:43AM +0300, Dan Carpenter wrote:
> On Wed, Feb 20, 2019 at 03:08:40AM +, 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
> > ---
> > 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
Re: [PATCH -next] btrfs: Fix type conversion in btrfs_read_root_item
On Wed, Feb 20, 2019 at 03:08:40AM +, 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
> ---
> 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
Re: [PATCH -next] btrfs: Fix type conversion in btrfs_read_root_item
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
> ---
> 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)
>
>
>
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