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    Subject[PATCH v2 03/10] ovl: check privs before decoding file handle
    Date
    CAP_DAC_READ_SEARCH is required by open_by_handle_at(2) so check it in
    ovl_decode_real_fh() as well to prevent privilege escalation for
    unprivileged overlay mounts.

    Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
    ---
    fs/overlayfs/namei.c | 3 +++
    1 file changed, 3 insertions(+)

    diff --git a/fs/overlayfs/namei.c b/fs/overlayfs/namei.c
    index a6162c4076db..82a55fdb1e7a 100644
    --- a/fs/overlayfs/namei.c
    +++ b/fs/overlayfs/namei.c
    @@ -156,6 +156,9 @@ struct dentry *ovl_decode_real_fh(struct ovl_fh *fh, struct vfsmount *mnt,
    struct dentry *real;
    int bytes;

    + if (!capable(CAP_DAC_READ_SEARCH))
    + return NULL;
    +
    /*
    * Make sure that the stored uuid matches the uuid of the lower
    * layer where file handle will be decoded.
    --
    2.26.2
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