[ck] Re: [4.19 PATCH] fuse: add FUSE_WRITE_KILL_PRIV

From: Miklos Szeredi <mszeredi(a)redhat.com> commit 4a2abf99f9c2877039006b8dfb3ec4e0d1278fe8 upstream In the FOPEN_DIRECT_IO case the write path doesn't call file_remove_privs() and that means setuid bit is not cleared if unpriviliged user writes to a file with setuid bit set. pjdfstest chmod test 12.t tests this and fails. Fix this by adding a flag to the FUSE_WRITE message that requests clearing privileges on the given file. This needs This better than just calling fuse_remove_privs(), because the attributes may not be up to date, so in that case a write may miss clearing the privileges. Test case: $ passthrough_ll /mnt/pasthrough-mnt -o default_permissions,allow_other,cache=never $ mkdir /mnt/pasthrough-mnt/testdir $ cd /mnt/pasthrough-mnt/testdir $ prove -rv pjdfstests/tests/chmod/12.t Reported-by: Vivek Goyal <vgoyal(a)redhat.com> Signed-off-by: Miklos Szeredi <mszeredi(a)redhat.com> Tested-by: Vivek Goyal <vgoyal(a)redhat.com> Signed-off-by: Jeffle Xu <jefflexu(a)linux.alibaba.com>