Messages in this thread | | | Subject | Re: [PATCH] btrfs: fix a NULL pointer dereference | From | Qu Wenruo <> | Date | Thu, 14 Mar 2019 17:15:42 +0800 |
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On 2019/3/14 下午4:03, Nikolay Borisov wrote: > > > On 14.03.19 г. 10:02 ч., Qu Wenruo wrote: >> >> >> On 2019/3/14 下午3:54, Nikolay Borisov wrote: >>> >>> >>> On 14.03.19 г. 9:50 ч., Kangjie Lu wrote: >>>> btrfs_lookup_block_group may fail and return NULL. The fix goes >>>> to out when it fails to avoid NULL pointer dereference. >>> >>> Actually no, in this case btrfs_lookup_block_group must never fail >>> because if we have an allocated eb then it must have been allocated from >>> a bg. >> >> Yep, that's the normal case. >> >> However I'm wondering if it's possible to get a bad eb which is cached. >> >> Then we could hit such situation. >> >> So I still believe being safe here still makes sense, especially who >> knows future fuzzed image will be. > > Then I'd rather have ASSERT(cache)
Isn't assert() a bad idea for production build without assert() support?
Thanks, Qu
> >> >> Thanks, >> Qu >> >>> >>>> >>>> Signed-off-by: Kangjie Lu <kjlu@umn.edu> >>>> --- >>>> fs/btrfs/extent-tree.c | 2 ++ >>>> 1 file changed, 2 insertions(+) >>>> >>>> diff --git a/fs/btrfs/extent-tree.c b/fs/btrfs/extent-tree.c >>>> index 994f0cc41799..b1e7985bcb9d 100644 >>>> --- a/fs/btrfs/extent-tree.c >>>> +++ b/fs/btrfs/extent-tree.c >>>> @@ -7303,6 +7303,8 @@ void btrfs_free_tree_block(struct btrfs_trans_handle *trans, >>>> >>>> pin = 0; >>>> cache = btrfs_lookup_block_group(fs_info, buf->start); >>>> + if (!cache) >>>> + goto out; >>>> >>>> if (btrfs_header_flag(buf, BTRFS_HEADER_FLAG_WRITTEN)) { >>>> pin_down_extent(fs_info, cache, buf->start, >>>> >>
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