6.6-stable review patch. If anyone has any objections, please let me know.
------------------
From: Florian Westphal fw@strlen.de
commit 7f3287db654395f9c5ddd246325ff7889f550286 upstream.
When running in container environmment, /sys/fs/cgroup/ might not be the real root node of the sk-attached cgroup.
Example:
In container: % stat /sys//fs/cgroup/ Device: 0,21 Inode: 2214 .. % stat /sys/fs/cgroup/foo Device: 0,21 Inode: 2264 ..
The expectation would be for:
nft add rule .. socket cgroupv2 level 1 "foo" counter
to match traffic from a process that got added to "foo" via "echo $pid > /sys/fs/cgroup/foo/cgroup.procs".
However, 'level 3' is needed to make this work.
Seen from initial namespace, the complete hierarchy is:
% stat /sys/fs/cgroup/system.slice/docker-.../foo Device: 0,21 Inode: 2264 ..
i.e. hierarchy is 0 1 2 3 / -> system.slice -> docker-1... -> foo
... but the container doesn't know that its "/" is the "docker-1.." cgroup. Current code will retrieve the 'system.slice' cgroup node and store its kn->id in the destination register, so compare with 2264 ("foo" cgroup id) will not match.
Fetch "/" cgroup from ->init() and add its level to the level we try to extract. cgroup root-level is 0 for the init-namespace or the level of the ancestor that is exposed as the cgroup root inside the container.
In the above case, cgrp->level of "/" resolved in the container is 2 (docker-1...scope/) and request for 'level 1' will get adjusted to fetch the actual level (3).
v2: use CONFIG_SOCK_CGROUP_DATA, eval function depends on it. (kernel test robot)
Cc: cgroups@vger.kernel.org Fixes: e0bb96db96f8 ("netfilter: nft_socket: add support for cgroupsv2") Reported-by: Nadia Pinaeva n.m.pinaeva@gmail.com Signed-off-by: Florian Westphal fw@strlen.de Signed-off-by: Pablo Neira Ayuso pablo@netfilter.org Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- net/netfilter/nft_socket.c | 41 ++++++++++++++++++++++++++++++++++++++--- 1 file changed, 38 insertions(+), 3 deletions(-)
--- a/net/netfilter/nft_socket.c +++ b/net/netfilter/nft_socket.c @@ -9,7 +9,8 @@
struct nft_socket { enum nft_socket_keys key:8; - u8 level; + u8 level; /* cgroupv2 level to extract */ + u8 level_user; /* cgroupv2 level provided by userspace */ u8 len; union { u8 dreg; @@ -53,6 +54,28 @@ nft_sock_get_eval_cgroupv2(u32 *dest, st memcpy(dest, &cgid, sizeof(u64)); return true; } + +/* process context only, uses current->nsproxy. */ +static noinline int nft_socket_cgroup_subtree_level(void) +{ + struct cgroup *cgrp = cgroup_get_from_path("/"); + int level; + + if (!cgrp) + return -ENOENT; + + level = cgrp->level; + + cgroup_put(cgrp); + + if (WARN_ON_ONCE(level > 255)) + return -ERANGE; + + if (WARN_ON_ONCE(level < 0)) + return -EINVAL; + + return level; +} #endif
static struct sock *nft_socket_do_lookup(const struct nft_pktinfo *pkt) @@ -174,9 +197,10 @@ static int nft_socket_init(const struct case NFT_SOCKET_MARK: len = sizeof(u32); break; -#ifdef CONFIG_CGROUPS +#ifdef CONFIG_SOCK_CGROUP_DATA case NFT_SOCKET_CGROUPV2: { unsigned int level; + int err;
if (!tb[NFTA_SOCKET_LEVEL]) return -EINVAL; @@ -185,6 +209,17 @@ static int nft_socket_init(const struct if (level > 255) return -EOPNOTSUPP;
+ err = nft_socket_cgroup_subtree_level(); + if (err < 0) + return err; + + priv->level_user = level; + + level += err; + /* Implies a giant cgroup tree */ + if (WARN_ON_ONCE(level > 255)) + return -EOPNOTSUPP; + priv->level = level; len = sizeof(u64); break; @@ -209,7 +244,7 @@ static int nft_socket_dump(struct sk_buf if (nft_dump_register(skb, NFTA_SOCKET_DREG, priv->dreg)) return -1; if (priv->key == NFT_SOCKET_CGROUPV2 && - nla_put_be32(skb, NFTA_SOCKET_LEVEL, htonl(priv->level))) + nla_put_be32(skb, NFTA_SOCKET_LEVEL, htonl(priv->level_user))) return -1; return 0; }