On 2018年07月02日 16:01, Nikolay Borisov wrote:
>
>
> On 2.07.2018 10:53, Qu Wenruo wrote:
>>
>>
>> On 2018年07月02日 15:31, Nikolay Borisov wrote:
>>>
>>>
>>> On 2.07.2018 09:25, Qu Wenruo wrote:
>>>> Reported in https://bugzilla.kernel.org/show_bug.cgi?id=199833, where an
>>>> invalid tree reloc tree can cause kernel NULL pointer dereference when
>>>> btrfs does some cleanup for reloc roots.
>>>>
>>>> It turns out that fs_info->reloc_ctl can be NULL in
>>>> btrfs_recover_relocation() as we allocate relocation control after all
>>>> reloc roots are verified.
>>>> So when we hit out: tag, we haven't call set_reloc_control() thus
>>>> fs_info->reloc_ctl is still NULL.
>>>>
>>>> Reported-by: Xu Wen <wen...@gatech.edu>
>>>> Signed-off-by: Qu Wenruo <w...@suse.com>
>>>> ---
>>>> fs/btrfs/relocation.c | 23 ++++++++++++-----------
>>>> 1 file changed, 12 insertions(+), 11 deletions(-)
>>>>
>>>> diff --git a/fs/btrfs/relocation.c b/fs/btrfs/relocation.c
>>>> index 879b76fa881a..be94c65bb4d2 100644
>>>> --- a/fs/btrfs/relocation.c
>>>> +++ b/fs/btrfs/relocation.c
>>>> @@ -1321,18 +1321,19 @@ static void __del_reloc_root(struct btrfs_root
>>>> *root)
>>>> struct mapping_node *node = NULL;
>>>> struct reloc_control *rc = fs_info->reloc_ctl;
>>>> > - spin_lock(&rc->reloc_root_tree.lock);
>>>> - rb_node = tree_search(&rc->reloc_root_tree.rb_root,
>>>> - root->node->start);
>>>> - if (rb_node) {
>>>> - node = rb_entry(rb_node, struct mapping_node, rb_node);
>>>> - rb_erase(&node->rb_node, &rc->reloc_root_tree.rb_root);
>>>
>>> Just do if (!rc)
>>> return;
>>>
>>> The function is simple enough, no need to indent multiple lines.
>>
>> You missed serval lines below, we still have:
>> ---
>> spin_lock(&fs_info->trans_lock);
>> list_del_init(&root->root_list);
>> spin_unlock(&fs_info->trans_lock);
>> kfree(node);
>> ---
>>
>> Which still needs to be called even rc is not initialized.
>
> But then isn't the function buggy even with your patch because if node
> is not initialised then we exit at if (!node) return.
That means node->data isn't initialized nor its root->root_list.
The patch only needs to call list_del_init() if @rc is not initialized.
Thanks,
Qu
>>
>> Thanks,
>> Qu
>>
>>>> + if (rc) {
>>>> + spin_lock(&rc->reloc_root_tree.lock);
>>>> + rb_node = tree_search(&rc->reloc_root_tree.rb_root,
>>>> + root->node->start);
>>>> + if (rb_node) {
>>>> + node = rb_entry(rb_node, struct mapping_node, rb_node);
>>>> + rb_erase(&node->rb_node, &rc->reloc_root_tree.rb_root);
>>>> + }
>>>> + spin_unlock(&rc->reloc_root_tree.lock);
>>>> + if (!node)
>>>> + return;
>>>> + BUG_ON((struct btrfs_root *)node->data != root);
>>>> }
>>>> - spin_unlock(&rc->reloc_root_tree.lock);
>>>> -
>>>> - if (!node)
>>>> - return;
>>>> - BUG_ON((struct btrfs_root *)node->data != root);
>>>>
>>>> spin_lock(&fs_info->trans_lock);
>>>> list_del_init(&root->root_list);
>>>>
>>> --
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>>
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