[dm-devel] [PATCH] bcachefs: fix NULL pointer dereference in try_alloc_bucket

[Kent Overstreet]

On Tue, May 30, 2023 at 08:15:41AM -0400, Mikulas Patocka wrote:
> 
> 
> On Mon, 29 May 2023, Mikulas Patocka wrote:
> 
> > The oops happens in set_btree_iter_dontneed and it is caused by the fact 
> > that iter->path is NULL. The code in try_alloc_bucket is buggy because it 
> > sets "struct btree_iter iter = { NULL };" and then jumps to the "err" 
> > label that tries to dereference values in "iter".
> 
> Here I'm sending a patch for it.
> 
> 
> 
> +		set_btree_iter_dontneed(&iter);
>  	bch2_trans_iter_exit(trans, &iter);

I need to look at this code a bit more, perhaps we'll want to move the
check into set_btree_iter_dontneed(), since iter_exit() is safe to call
on an uninitialized-but-zeroed iterator