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    SubjectRe: [PATCH AUTOSEL 4.19 33/57] blk-mq: protect debugfs_create_files() from failures
    On Fri, Mar 29, 2019 at 09:28:26PM -0400, Sasha Levin wrote:
    > From: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
    >
    > [ Upstream commit 36991ca68db9dd43bac7f3519f080ee3939263ef ]
    >
    > If debugfs were to return a non-NULL error for a debugfs call, using
    > that pointer later in debugfs_create_files() would crash.
    >
    > Fix that by properly checking the pointer before referencing it.
    >
    > Reported-by: Michal Hocko <mhocko@kernel.org>
    > Reported-and-tested-by: syzbot+b382ba6a802a3d242790@syzkaller.appspotmail.com
    > Reported-by: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
    > Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
    > Signed-off-by: Sasha Levin <sashal@kernel.org>
    > ---
    > block/blk-mq-debugfs.c | 3 +++
    > 1 file changed, 3 insertions(+)
    >
    > diff --git a/block/blk-mq-debugfs.c b/block/blk-mq-debugfs.c
    > index cb1e6cf7ac48..9dc3a0896462 100644
    > --- a/block/blk-mq-debugfs.c
    > +++ b/block/blk-mq-debugfs.c
    > @@ -806,6 +806,9 @@ static const struct blk_mq_debugfs_attr blk_mq_debugfs_ctx_attrs[] = {
    > static bool debugfs_create_files(struct dentry *parent, void *data,
    > const struct blk_mq_debugfs_attr *attr)
    > {
    > + if (IS_ERR_OR_NULL(parent))
    > + return false;
    > +
    > d_inode(parent)->i_private = data;
    >
    > for (; attr->name; attr++) {
    > --
    > 2.19.1
    >

    This was a 5.0-only thing, no need for it to be backported anywhere.
    Please drop it from all of your trees.

    thanks,

    greg k-h

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