daandemeyer / rpms / systemd

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From 084d0849fc864b0377551b211def7a89b642c5e9 Mon Sep 17 00:00:00 2001
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From: Julia Kartseva <hex@fb.com>
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Date: Thu, 4 Nov 2021 18:52:02 -0700
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Subject: [PATCH 1/2] core: fix bpf-foreign cg controller realization
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Requiring /sys/fs/bpf path to be a mount point at the moment of cgroup
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controllers realization does more harm than good, because:
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* Realization happens early on boot, the mount point may not be ready at
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the time. That happens if mounts are made by a .mount unit (the issue we
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encountered).
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* BPF filesystem may be mounted on another point.
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Remove the check. Instead verify that path provided by BPFProgram= is
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within BPF fs when unit properties are parsed.
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Split in two commits for simple backport.
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---
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 src/core/bpf-foreign.c | 10 ----------
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 src/core/bpf-foreign.h |  5 ++++-
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 2 files changed, 4 insertions(+), 11 deletions(-)
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diff --git a/src/core/bpf-foreign.c b/src/core/bpf-foreign.c
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index 6b93b9785fb5..686c14ce1f18 100644
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--- a/src/core/bpf-foreign.c
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+++ b/src/core/bpf-foreign.c
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@@ -111,16 +111,6 @@ static int bpf_foreign_prepare(
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         return 0;
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 }
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-int bpf_foreign_supported(void) {
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-        int r;
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-
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-        r = cg_all_unified();
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-        if (r <= 0)
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-                return r;
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-
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-        return path_is_mount_point("/sys/fs/bpf", NULL, 0);
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-}
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-
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 int bpf_foreign_install(Unit *u) {
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         _cleanup_free_ char *cgroup_path = NULL;
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         CGroupBPFForeignProgram *p;
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diff --git a/src/core/bpf-foreign.h b/src/core/bpf-foreign.h
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index 9559cd79812b..e387b1b1d389 100644
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--- a/src/core/bpf-foreign.h
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+++ b/src/core/bpf-foreign.h
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@@ -4,7 +4,10 @@
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 #include "unit.h"
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-int bpf_foreign_supported(void);
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+static inline int bpf_foreign_supported(void) {
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+        return cg_all_unified();
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+}
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+
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 /*
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  * Attach cgroup-bpf programs foreign to systemd, i.e. loaded to the kernel by an entity
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  * external to systemd.
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From dedca960afdee5797d19929c43853513711e3e3d Mon Sep 17 00:00:00 2001
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From: Julia Kartseva <hex@fb.com>
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Date: Thu, 4 Nov 2021 18:55:55 -0700
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Subject: [PATCH 2/2] core: check fs type of BPFProgram= property path
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Tests:
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```
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% stat --file-system --format="%T" /root/bpf/trivial/
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bpf_fs
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% systemd-nspawn -D/ --volatile=yes \
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--property=BPFProgram=egress:/root/bpf/trivial/cgroup_skb_egress \
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--quiet -- ping -c 5 -W 1 ::1
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PING ::1(::1) 56 data bytes
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--- ::1 ping statistics ---
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5 packets transmitted, 0 received, 100% packet loss, time 4110ms
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```
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```
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% stat --file-system --format='%T' /root/meh
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btrfs
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% systemd-nspawn -D/ --volatile=yes --property=BPFProgram=egress:/root/meh
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--quiet -- ping -c 5 -W 1 ::1
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```
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sudo ./build/systemd-nspawn \
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-D/ --volatile=yes --property=BPFProgram=egress:/home/hex --quiet -- \
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ping -c 1 -W 1 ::1
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PING ::1(::1) 56 data bytes
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64 bytes from ::1: icmp_seq=1 ttl=64 time=0.017 ms
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--- ::1 ping statistics ---
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1 packets transmitted, 1 received, 0% packet loss, time 0ms
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---
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 src/core/bpf-foreign.c | 10 ++++++++++
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 1 file changed, 10 insertions(+)
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diff --git a/src/core/bpf-foreign.c b/src/core/bpf-foreign.c
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index 686c14ce1f18..8538792b60db 100644
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--- a/src/core/bpf-foreign.c
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+++ b/src/core/bpf-foreign.c
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@@ -4,8 +4,10 @@
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 #include "bpf-program.h"
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 #include "cgroup.h"
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 #include "memory-util.h"
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+#include "missing_magic.h"
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 #include "mountpoint-util.h"
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 #include "set.h"
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+#include "stat-util.h"
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 typedef struct BPFForeignKey BPFForeignKey;
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 struct BPFForeignKey {
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@@ -84,6 +86,14 @@ static int bpf_foreign_prepare(
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         assert(u);
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         assert(bpffs_path);
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+        r = path_is_fs_type(bpffs_path, BPF_FS_MAGIC);
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+        if (r < 0)
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+                return log_unit_error_errno(u, r,
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+                                "Failed to determine filesystem type of %s: %m", bpffs_path);
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+        if (r == 0)
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+                return log_unit_error_errno(u, SYNTHETIC_ERRNO(EINVAL),
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+                                "Path in BPF filesystem is expected.");
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+
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         r = bpf_program_new_from_bpffs_path(bpffs_path, &prog;;
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         if (r < 0)
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                 return log_unit_error_errno(u, r, "Failed to create foreign BPFProgram: %m");