Re: [PATCH bpf-next v2 0/2] Fix cgroup attach flags being assigned to effective progs

[Martin KaFai Lau]

On 9/8/22 10:28 AM, sdf@xxxxxxxxxx wrote:
> On 09/08, Pu Lehui wrote:
> > From: Pu Lehui <pulehui@xxxxxxxxxx>
>
> > When root-cgroup attach multi progs and sub-cgroup attach a
> > override prog, bpftool will display incorrectly for the attach
> > flags of the sub-cgroup’s effective progs:
>
> > $ bpftool cgroup tree /sys/fs/cgroup effective
> > CgroupPath
> > ID       AttachType      AttachFlags     Name
> > /sys/fs/cgroup
> > 6        cgroup_sysctl   multi           sysctl_tcp_mem
> > 13       cgroup_sysctl   multi           sysctl_tcp_mem
> > /sys/fs/cgroup/cg1
> > 20       cgroup_sysctl   override        sysctl_tcp_mem
> > 6        cgroup_sysctl   override        sysctl_tcp_mem <- wrong
> > 13       cgroup_sysctl   override        sysctl_tcp_mem <- wrong
> > /sys/fs/cgroup/cg1/cg2
> > 20       cgroup_sysctl                   sysctl_tcp_mem
> > 6        cgroup_sysctl                   sysctl_tcp_mem
> > 13       cgroup_sysctl                   sysctl_tcp_mem
>
> > For cg1, obviously, the attach flags of prog6 and prog13 can not be
> > OVERRIDE, and the attach flags of prog6 and prog13 is meaningless for
> > cg1. We only need to care the attach flags of prog which attached to
> > cg1, other progs attach flags should be omit. After these patches,
> > the above situation will show as bellow:
>
> > $ bpftool cgroup tree /sys/fs/cgroup effective
> > CgroupPath
> > ID       AttachType      AttachFlags     Name
> > /sys/fs/cgroup
> > 6        cgroup_sysctl   multi           sysctl_tcp_mem
> > 13       cgroup_sysctl   multi           sysctl_tcp_mem
> > /sys/fs/cgroup/cg1
> > 20       cgroup_sysctl   override        sysctl_tcp_mem
> > 6        cgroup_sysctl                   sysctl_tcp_mem
> > 13       cgroup_sysctl                   sysctl_tcp_mem
> > /sys/fs/cgroup/cg1/cg2
> > 20       cgroup_sysctl                   sysctl_tcp_mem
> > 6        cgroup_sysctl                   sysctl_tcp_mem
> > 13       cgroup_sysctl                   sysctl_tcp_mem
>
> > v2:
> > - Limit prog_cnt to avoid overflow. (John)
> > - Add more detail message.
>
> John also raised a good question in v1: the flags don't seem to
> make sense when requesting effective list. So maybe not export them
> at all?
+1. not exporting them for 'effective' listing makes sense.

This seems to be the day one behavior instead of the recent 
prog_attach_flags changes? so bpf-next makes sense also.