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.xu@xxxxxxxxxx> >>>> Signed-off-by: Qu Wenruo <wqu@xxxxxxxx> >>>> --- >>>> 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); >>>> >>> -- >>> To unsubscribe from this list: send the line "unsubscribe linux-btrfs" in >>> the body of a message to majordomo@xxxxxxxxxxxxxxx >>> More majordomo info at http://vger.kernel.org/majordomo-info.html >>> >> > -- > To unsubscribe from this list: send the line "unsubscribe linux-btrfs" in > the body of a message to majordomo@xxxxxxxxxxxxxxx > More majordomo info at http://vger.kernel.org/majordomo-info.html > -- To unsubscribe from this list: send the line "unsubscribe linux-btrfs" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
