Re: [PATCH v2] bcachefs: fix null-ptr-deref in have_stripes()

[Alan Huang]

On Oct 26, 2024, at 00:54, Kent Overstreet <kent.overstreet@xxxxxxxxx> wrote:
> 
> On Fri, Oct 25, 2024 at 08:56:18PM +0900, Jeongjun Park wrote:
>> c->btree_roots_known[i].b can be NULL. In this case, a NULL pointer dereference
>> occurs, so you need to add code to check the variable.
>> 
>> Reported-by: syzbot+b468b9fef56949c3b528@xxxxxxxxxxxxxxxxxxxxxxxxx
>> Fixes: 7773df19c35f ("bcachefs: metadata version bucket_stripe_sectors")
>> Signed-off-by: Jeongjun Park <aha310510@xxxxxxxxx>
> 
> This looks identical to the v1? It's already in my testing branch

This version fix the “Fixes" tag, the original one is:

"Fixes: ("bcachefs: metadata version bucket_stripe_sectors”)"

> 
> (But it should be in my hotfix branch, doing that now)
> 
>> ---
>> fs/bcachefs/sb-downgrade.c | 3 +++
>> 1 file changed, 3 insertions(+)
>> 
>> diff --git a/fs/bcachefs/sb-downgrade.c b/fs/bcachefs/sb-downgrade.c
>> index ae715ff658e8..8767c33c2b51 100644
>> --- a/fs/bcachefs/sb-downgrade.c
>> +++ b/fs/bcachefs/sb-downgrade.c
>> @@ -143,6 +143,9 @@ UPGRADE_TABLE()
>> 
>> static int have_stripes(struct bch_fs *c)
>> {
>> + if (IS_ERR_OR_NULL(c->btree_roots_known[BTREE_ID_stripes].b))
>> + return 0;
>> +
>> return !btree_node_fake(c->btree_roots_known[BTREE_ID_stripes].b);
>> }
>> 
>> --
>