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

[sdf]

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?

> v1:
> https://lore.kernel.org/bpf/20220820120234.2121044-1-pulehui@xxxxxxxxxx

> Pu Lehui (2):
>    bpf, cgroup: Fix attach flags being assigned to effective progs
>    bpftool: Fix cgroup attach flags being assigned to effective progs

>   kernel/bpf/cgroup.c        | 5 ++++-
>   tools/bpf/bpftool/cgroup.c | 9 +++------
>   2 files changed, 7 insertions(+), 7 deletions(-)

> --
> 2.25.1