From: Juntong Deng <juntong.deng@outlook.com>
Date: Mon, 14 Oct 2024 09:21:08 +0000 (+0100)
Subject: bpf: Add bpf_task_from_vpid() kfunc
X-Git-Tag: v6.13-rc1~136^2~50
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=675c3596ff32c040d1dd2e28dd57e83e634b9f60;p=thirdparty%2Flinux.git

bpf: Add bpf_task_from_vpid() kfunc

bpf_task_from_pid() that currently exists looks up the
struct task_struct corresponding to the pid in the root pid
namespace (init_pid_ns).

This patch adds bpf_task_from_vpid() which looks up the
struct task_struct corresponding to vpid in the pid namespace
of the current process.

This is useful for getting information about other processes
in the same pid namespace.

Signed-off-by: Juntong Deng <juntong.deng@outlook.com>
Link: https://lore.kernel.org/r/AM6PR03MB5848E50DA58F79CDE65433C399442@AM6PR03MB5848.eurprd03.prod.outlook.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
---

diff --git a/kernel/bpf/helpers.c b/kernel/bpf/helpers.c
index aaaefefdf692b..073e6f04f4d76 100644
--- a/kernel/bpf/helpers.c
+++ b/kernel/bpf/helpers.c
@@ -2521,6 +2521,25 @@ __bpf_kfunc struct task_struct *bpf_task_from_pid(s32 pid)
 	return p;
 }
 
+/**
+ * bpf_task_from_vpid - Find a struct task_struct from its vpid by looking it up
+ * in the pid namespace of the current task. If a task is returned, it must
+ * either be stored in a map, or released with bpf_task_release().
+ * @vpid: The vpid of the task being looked up.
+ */
+__bpf_kfunc struct task_struct *bpf_task_from_vpid(s32 vpid)
+{
+	struct task_struct *p;
+
+	rcu_read_lock();
+	p = find_task_by_vpid(vpid);
+	if (p)
+		p = bpf_task_acquire(p);
+	rcu_read_unlock();
+
+	return p;
+}
+
 /**
  * bpf_dynptr_slice() - Obtain a read-only pointer to the dynptr data.
  * @p: The dynptr whose data slice to retrieve
@@ -3034,6 +3053,7 @@ BTF_ID_FLAGS(func, bpf_task_under_cgroup, KF_RCU)
 BTF_ID_FLAGS(func, bpf_task_get_cgroup1, KF_ACQUIRE | KF_RCU | KF_RET_NULL)
 #endif
 BTF_ID_FLAGS(func, bpf_task_from_pid, KF_ACQUIRE | KF_RET_NULL)
+BTF_ID_FLAGS(func, bpf_task_from_vpid, KF_ACQUIRE | KF_RET_NULL)
 BTF_ID_FLAGS(func, bpf_throw)
 BTF_KFUNCS_END(generic_btf_ids)