linux.git/kernel/bpf/cgroup_iter.c, branch v6.1.84

cgroup: bpf: use cgroup_lock()/cgroup_unlock() wrappers

2023-06-21T14:00:51+00:00

[ Upstream commit 4cdb91b0dea7d7f59fa84a13c7753cd434fdedcf ]

Replace mutex_[un]lock() with cgroup_[un]lock() wrappers to stay
consistent across cgroup core and other subsystem code, while
operating on the cgroup_mutex.

Signed-off-by: Kamalesh Babulal 
Acked-by: Alexei Starovoitov 
Reviewed-by: Christian Brauner 
Signed-off-by: Tejun Heo 
Stable-dep-of: 2bd110339288 ("cgroup: always put cset in cgroup_css_set_put_fork")
Signed-off-by: Sasha Levin

bpf: Pin the start cgroup in cgroup_iter_seq_init()

2022-12-31T12:32:13+00:00

[ Upstream commit 1a5160d4d8fe63ba4964cfff4a85831b6af75f2d ]

bpf_iter_attach_cgroup() has already acquired an extra reference for the
start cgroup, but the reference may be released if the iterator link fd
is closed after the creation of iterator fd, and it may lead to
user-after-free problem when reading the iterator fd.

An alternative fix is pinning iterator link when opening iterator,
but it will make iterator link being still visible after the close of
iterator link fd and the behavior is different with other link types, so
just fixing it by acquiring another reference for the start cgroup.

Fixes: d4ccaf58a847 ("bpf: Introduce cgroup iter")
Signed-off-by: Hou Tao 
Signed-off-by: Daniel Borkmann 
Acked-by: Yonghong Song 
Link: https://lore.kernel.org/bpf/20221121073440.1828292-2-houtao@huaweicloud.com
Signed-off-by: Sasha Levin

bpf: cgroup_iter: support cgroup1 using cgroup fd

2022-10-11T16:50:15+00:00

Use cgroup_v1v2_get_from_fd() in cgroup_iter to support attaching to
both cgroup v1 and v2 using fds.

Signed-off-by: Yosry Ahmed 
Acked-by: Martin KaFai Lau 
Signed-off-by: Tejun Heo

bpf: Remove useless else if

2022-09-01T21:04:07+00:00

The assignment of the else and else if branches is the same, so the else
if here is redundant, so we remove it and add a comment to make the code
here readable.

./kernel/bpf/cgroup_iter.c:81:6-8: WARNING: possible condition with no effect (if == else).

Link: https://bugzilla.openanolis.cn/show_bug.cgi?id=2016
Reported-by: Abaci Robot 
Signed-off-by: Jiapeng Chong 
Link: https://lore.kernel.org/r/20220831021618.86770-1-jiapeng.chong@linux.alibaba.com
Signed-off-by: Martin KaFai Lau

bpf: Add CGROUP prefix to cgroup_iter_order

2022-08-25T23:26:37+00:00

bpf_cgroup_iter_order is globally visible but the entries do not have
CGROUP prefix. As requested by Andrii, put a CGROUP in the names
in bpf_cgroup_iter_order.

This patch fixes two previous commits: one introduced the API and
the other uses the API in bpf selftest (that is, the selftest
cgroup_hierarchical_stats).

I tested this patch via the following command:

  test_progs -t cgroup,iter,btf_dump

Fixes: d4ccaf58a847 ("bpf: Introduce cgroup iter")
Fixes: 88886309d2e8 ("selftests/bpf: add a selftest for cgroup hierarchical stats collection")
Suggested-by: Andrii Nakryiko 
Acked-by: Andrii Nakryiko 
Signed-off-by: Hao Luo 
Link: https://lore.kernel.org/r/20220825223936.1865810-1-haoluo@google.com
Signed-off-by: Martin KaFai Lau

bpf: Introduce cgroup iter

2022-08-25T18:35:37+00:00

Cgroup_iter is a type of bpf_iter. It walks over cgroups in four modes:

 - walking a cgroup's descendants in pre-order.
 - walking a cgroup's descendants in post-order.
 - walking a cgroup's ancestors.
 - process only the given cgroup.

When attaching cgroup_iter, one can set a cgroup to the iter_link
created from attaching. This cgroup is passed as a file descriptor
or cgroup id and serves as the starting point of the walk. If no
cgroup is specified, the starting point will be the root cgroup v2.

For walking descendants, one can specify the order: either pre-order or
post-order. For walking ancestors, the walk starts at the specified
cgroup and ends at the root.

One can also terminate the walk early by returning 1 from the iter
program.

Note that because walking cgroup hierarchy holds cgroup_mutex, the iter
program is called with cgroup_mutex held.

Currently only one session is supported, which means, depending on the
volume of data bpf program intends to send to user space, the number
of cgroups that can be walked is limited. For example, given the current
buffer size is 8 * PAGE_SIZE, if the program sends 64B data for each
cgroup, assuming PAGE_SIZE is 4kb, the total number of cgroups that can
be walked is 512. This is a limitation of cgroup_iter. If the output
data is larger than the kernel buffer size, after all data in the
kernel buffer is consumed by user space, the subsequent read() syscall
will signal EOPNOTSUPP. In order to work around, the user may have to
update their program to reduce the volume of data sent to output. For
example, skip some uninteresting cgroups. In future, we may extend
bpf_iter flags to allow customizing buffer size.

Acked-by: Yonghong Song 
Acked-by: Tejun Heo 
Signed-off-by: Hao Luo 
Link: https://lore.kernel.org/r/20220824233117.1312810-2-haoluo@google.com
Signed-off-by: Alexei Starovoitov