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    SubjectRe: [PATCH] btrfs: Fix btrfs_block_group refcnt leak
    On Tue, Apr 21, 2020 at 12:43:15AM +0200, David Sterba wrote:
    > On Mon, Apr 20, 2020 at 01:38:40PM +0800, Xiyu Yang wrote:
    > > btrfs_remove_block_group() invokes btrfs_lookup_block_group(), which
    > > returns a local reference of the blcok group that contains the given
    > > bytenr to "block_group" with increased refcount.
    > >
    > > When btrfs_remove_block_group() returns, "block_group" becomes invalid,
    > > so the refcount should be decreased to keep refcount balanced.
    > >
    > > The reference counting issue happens in several exception handling paths
    > > of btrfs_remove_block_group(). When those error scenarios occur such as
    > > btrfs_alloc_path() returns NULL, the function forgets to decrease its
    > > refcnt increased by btrfs_lookup_block_group() and will cause a refcnt
    > > leak.
    > >
    > > Fix this issue by jumping to "out_put_group" label and calling
    > > btrfs_put_block_group() when those error scenarios occur.
    > >
    > > Signed-off-by: Xiyu Yang <xiyuyang19@fudan.edu.cn>
    > > Signed-off-by: Xin Tan <tanxin.ctf@gmail.com>
    >
    > Thanks for the fix. May I ask if this was found by code inspection or by
    > some analysis tool?

    Thanks for your advice about the patch! We are looking for some automated ways
    to find this kind of bug.

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