Re: [PATCH] bcachefs: Fix use after free

[Alan Huang <mmpgouride@gmail.com>]

On Feb 11, 2025, at 00:28, Kent Overstreet <kent.overstreet@linux.dev> wrote:
> 
> On Mon, Feb 10, 2025 at 11:04:22AM +0800, Alan Huang wrote:
>> acc->k.data should be used with the lock hold:
> 
> <snipped>
> 
>> 
>> Signed-off-by: Alan Huang <mmpgouride@gmail.com>
> 
> 
> Test this with lockdep (you know how to edit the lists of tests the CI
> runs, right?

The lockdep test group is in the tests lists.

Or you mean add tests in the lockdep group ? 

> 
> mark_lock usage is a giant mess, and calling percpu_down_read()
> recursively by accident will mostly work, until it doesn't.
> 
>> ---
>> fs/bcachefs/disk_accounting.h | 2 ++
>> 1 file changed, 2 insertions(+)
>> 
>> diff --git a/fs/bcachefs/disk_accounting.h b/fs/bcachefs/disk_accounting.h
>> index 5360cbb3ec29..f4372cafea2e 100644
>> --- a/fs/bcachefs/disk_accounting.h
>> +++ b/fs/bcachefs/disk_accounting.h
>> @@ -210,11 +210,13 @@ static inline void bch2_accounting_mem_read_counters(struct bch_accounting_mem *
>> static inline void bch2_accounting_mem_read(struct bch_fs *c, struct bpos p,
>>    u64 *v, unsigned nr)
>> {
>> + percpu_down_read(&c->mark_lock);
>> struct bch_accounting_mem *acc = &c->accounting;
>> unsigned idx = eytzinger0_find(acc->k.data, acc->k.nr, sizeof(acc->k.data[0]),
>>       accounting_pos_cmp, &p);
>> 
>> bch2_accounting_mem_read_counters(acc, idx, v, nr, false);
>> + percpu_up_read(&c->mark_lock);
>> }
>> 
>> static inline struct bversion journal_pos_to_bversion(struct journal_res *res, unsigned offset)
>> -- 
>> 2.47.0
>>