Re: [PATCH AUTOSEL 5.10 16/27] btrfs: tree-checker: check item_size for dev_item

Su Yue
2022-02-18T12:02:20Z

On Fri 18 Feb 2022 at 11:36, Greg KH <greg@kroah.com> wrote:

> On Wed, Feb 09, 2022 at 01:40:52PM -0500, Sasha Levin wrote:
>> From: Su Yue <l@damenly.su>
>>
>> [ Upstream commit ea1d1ca4025ac6c075709f549f9aa036b5b6597d ]
>>
>> Check item size before accessing the device item to avoid out
>> of bound
>> access, similar to inode_item check.
>>
>> Signed-off-by: Su Yue <l@damenly.su>
>> Reviewed-by: David Sterba <dsterba@suse.com>
>> Signed-off-by: David Sterba <dsterba@suse.com>
>> Signed-off-by: Sasha Levin <sashal@kernel.org>
>> ---
>> fs/btrfs/tree-checker.c | 8 ++++++++
>> 1 file changed, 8 insertions(+)
>>
>> diff --git a/fs/btrfs/tree-checker.c b/fs/btrfs/tree-checker.c
>> index d4a3a56726aa8..4a5ee516845f7 100644
>> --- a/fs/btrfs/tree-checker.c
>> +++ b/fs/btrfs/tree-checker.c
>> @@ -947,6 +947,7 @@ static int check_dev_item(struct
>> extent_buffer *leaf,
>> struct btrfs_key *key, int slot)
>> {
>> struct btrfs_dev_item *ditem;
>> + const u32 item_size = btrfs_item_size(leaf, slot);
>>
>> if (key->objectid != BTRFS_DEV_ITEMS_OBJECTID) {
>> dev_item_err(leaf, slot,
>> @@ -954,6 +955,13 @@ static int check_dev_item(struct
>> extent_buffer *leaf,
>> key->objectid,
>> BTRFS_DEV_ITEMS_OBJECTID);
>> return -EUCLEAN;
>> }
>> +
>> + if (unlikely(item_size != sizeof(*ditem))) {
>> + dev_item_err(leaf, slot, "invalid item size: has
>> %u expect %zu",
>> + item_size, sizeof(*ditem));
>> + return -EUCLEAN;
>> + }
>> +
>> ditem = btrfs_item_ptr(leaf, slot, struct btrfs_dev_item);
>> if (btrfs_device_id(leaf, ditem) != key->offset) {
>> dev_item_err(leaf, slot,
>> --
>> 2.34.1
>>
>
> This adds a build warning, showing that the backport is not
> correct, so
> I'll go drop this :(
>
And the warning is
========================================================================
arch/x86/kernel/head_64.o: warning: objtool: .text+0x5:
unreachable instruction
fs/btrfs/tree-checker.c: In function
\342\200\230check_dev_item\342\200\231:
fs/btrfs/tree-checker.c:950:53: warning: passing argument 2 of
\342\200\230btrfs_item_size\342\200\231 makes pointer from integer
without a cast [-Wint-conversion]
950 | const u32 item_size = btrfs_item_size(leaf, slot);
| ^~~~
| |
| int
In file included from fs/btrfs/tree-checker.c:21:
fs/btrfs/ctree.h:1474:48: note: expected \342\200\230const struct
btrfs_item *\342\200\231 but argument is of type
\342\200\230int\342\200\231
1474 | const type *s)
\
| ~~~~~~~~~~~~^
fs/btrfs/ctree.h:1833:1: note: in expansion of macro
\342\200\230BTRFS_SETGET_FUNCS\342\200\231
1833 | BTRFS_SETGET_FUNCS(item_size, struct btrfs_item, size,
32);
| ^~~~~~~~~~~~~~~~~~
========================================================================

The upstream patchset[1] merged in 5.17-rc1, changed second
parameter
of btrfs_item_size() from btrfs_item * to int directly.
So yes, the backport is wrong.

I'm not familiar with stable backport progress. Should I file a
patch
using btrfs_item *? Or just drop it?

The patch is related to 0c982944af27d131d3b74242f3528169f66950ad
but
I wonder why the 0c98294 is not selected automatically.

Thanks.

[1]:
https://patchwork.kernel.org/project/linux-btrfs/cover/cover.1634842475.git.josef@toxicpanda.com/
--
Su
> thanks,
>
> greg k-h