[Devel] [PATCH hci-8.1 v3 2/5] ve: Introduce override_ve/revert_ve helpers

[Vladimir Riabchun <vladimir.riabchun@virtuozzo.com>]

These helpers mirror override_creds/revert_creds and are supposed to
be used together in cases when VE creds may be stored and later used
by the different VE task.

To keep task_ve consistent for other users, introduce a separate
task->overrided_ve field. Nobody should race on it since its
updates are supposed to go with override_creds, and non-current
processes shouldn't do this.

https://virtuozzo.atlassian.net/browse/VSTOR-142405
Signed-off-by: Vladimir Riabchun <vladimir.riabchun@virtuozzo.com>
---
 include/linux/sched.h |  1 +
 include/linux/ve.h    | 24 ++++++++++++++++++++++++
 kernel/capability.c   |  6 ++++--
 3 files changed, 29 insertions(+), 2 deletions(-)

diff --git a/include/linux/sched.h b/include/linux/sched.h
index 10545e470d3d..7f4e6b1fde38 100644
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -1065,6 +1065,7 @@ struct task_struct {
 #ifdef CONFIG_VE
 	struct ve_struct		*task_ve;
 	struct ve_namespace		*ve_ns;
+	struct ve_struct		*overrided_ve; /* NULL when no overrides */
 #endif
 #ifdef CONFIG_PREEMPT_RT
 	struct netdev_xmit		net_xmit;
diff --git a/include/linux/ve.h b/include/linux/ve.h
index 717567775f58..c07484b4eee2 100644
--- a/include/linux/ve.h
+++ b/include/linux/ve.h
@@ -295,6 +295,23 @@ static inline struct vdso_image *ve_get_vdso_64(struct ve_struct *ve)
 	return ve->vdso_64;
 }
 
+static inline struct ve_struct *override_ve(struct ve_struct *new_ve)
+{
+	struct ve_struct *old_ve = current->overrided_ve;
+
+	/* CT tasks are not supposed to switch VE context, this is a breach */
+	if (WARN_ON(new_ve != get_exec_env() && !ve_is_super(get_exec_env())))
+		return ERR_PTR(-EPERM);
+
+	current->overrided_ve = new_ve;
+	return old_ve;
+}
+
+static inline void revert_ve(struct ve_struct *orig_ve)
+{
+	current->overrided_ve = orig_ve;
+}
+
 #else	/* CONFIG_VE */
 #include <linux/init_task.h>
 #include <net/net_namespace.h>
@@ -405,6 +422,13 @@ static inline struct vdso_image *ve_get_vdso_64(struct ve_struct *ve)
 }
 #endif /* CONFIG_X86 */
 
+static inline struct ve_struct *override_ve(struct ve_struct *new_ve)
+{
+	return NULL;
+}
+
+static inline void revert_ve(struct ve_struct *orig_ve) {}
+
 #endif	/* CONFIG_VE */
 
 struct seq_file;
diff --git a/kernel/capability.c b/kernel/capability.c
index 34716847c6b8..6de4dcba2283 100644
--- a/kernel/capability.c
+++ b/kernel/capability.c
@@ -389,10 +389,11 @@ EXPORT_SYMBOL(ns_capable);
 bool ve_capable(int cap)
 {
 	struct cred *cred;
+	struct ve_struct *ve = current->overrided_ve ?: get_exec_env();
 	bool ret;
 
 	rcu_read_lock();
-	cred = get_exec_env()->init_cred;
+	cred = ve->init_cred;
 
 	if (cred == NULL) /* ve isn't running */
 		cred = ve0.init_cred;
@@ -406,10 +407,11 @@ bool ve_capable(int cap)
 bool ve_capable_noaudit(int cap)
 {
 	struct cred *cred;
+	struct ve_struct *ve = current->overrided_ve ?: get_exec_env();
 	bool ret;
 
 	rcu_read_lock();
-	cred = get_exec_env()->init_cred;
+	cred = ve->init_cred;
 
 	if (cred == NULL) /* ve isn't running */
 		cred = ve0.init_cred;

-- 
2.52.0

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