Re: [PATCH][next] afs: fix a dereference on pointer cell before cell is null checked

From: David Howells
Date: Tue Oct 27 2020 - 07:05:57 EST


Colin King <colin.king@xxxxxxxxxxxxx> wrote:

> @@ -606,7 +605,7 @@ void afs_unuse_cell(struct afs_net *net, struct afs_cell *cell, enum afs_cell_tr
>
> u = atomic_read(&cell->ref);
> a = atomic_dec_return(&cell->active);
> - trace_afs_cell(debug_id, u, a, reason);
> + trace_afs_cell(cell->debug_id, u, a, reason);

It's probably better to read cell->debug_id before calling
atomic_dec_return().

I have a patch for this based on a report by Dan Carpenter, so no need to send
a revised patch.

Thanks,
David