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.
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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