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

[Greg KH <greg@kroah.com>]

On Fri, Feb 18, 2022 at 07:25:20PM +0800, Su Yue wrote:
> 
> 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?

If you think this needs to be in the stable tree, yes please backport it
and send it to us.

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

No idea, if you think that is needed to, please send it to us.

thanks,

greg k-h