From: Jiri Kosina <jikos@kernel.org>
To: Thomas Gleixner <tglx@linutronix.de>,
Ingo Molnar <mingo@redhat.com>,
Peter Zijlstra <peterz@infradead.org>,
Josh Poimboeuf <jpoimboe@redhat.com>,
Andrea Arcangeli <aarcange@redhat.com>,
"Woodhouse, David" <dwmw@amazon.co.uk>
Cc: linux-kernel@vger.kernel.org, x86@kernel.org,
Oleg Nesterov <oleg@redhat.com>,
Tim Chen <tim.c.chen@linux.intel.com>
Subject: [PATCH v2 1/3] ptrace: Provide ___ptrace_may_access() that can be applied on arbitrary tasks
Date: Mon, 3 Sep 2018 14:45:20 +0200 (CEST) [thread overview]
Message-ID: <nycvar.YFH.7.76.1809031443150.25787@cbobk.fhfr.pm> (raw)
From: Jiri Kosina <jkosina@suse.cz>
Current ptrace_may_access() implementation assumes that the 'source' task
is always the caller (current).
Expose ___ptrace_may_access() that can be used to apply the check on arbitrary
tasks.
Originally-by: Tim Chen <tim.c.chen@linux.intel.com>
Signed-off-by: Jiri Kosina <jkosina@suse.cz>
---
include/linux/ptrace.h | 12 ++++++++++++
kernel/ptrace.c | 13 ++++++++++---
2 files changed, 22 insertions(+), 3 deletions(-)
diff --git a/include/linux/ptrace.h b/include/linux/ptrace.h
index 4f36431c380b..09744d4113fb 100644
--- a/include/linux/ptrace.h
+++ b/include/linux/ptrace.h
@@ -87,6 +87,18 @@ extern void exit_ptrace(struct task_struct *tracer, struct list_head *dead);
*/
extern bool ptrace_may_access(struct task_struct *task, unsigned int mode);
+/**
+ * ___ptrace_may_access - variant of ptrace_may_access that can be used
+ * between two arbitrary tasks
+ * @curr: source task
+ * @task: target task
+ * @mode: selects type of access and caller credentials
+ *
+ * Returns true on success, false on denial.
+ */
+extern int ___ptrace_may_access(struct task_struct *curr, struct task_struct *task,
+ unsigned int mode);
+
static inline int ptrace_reparented(struct task_struct *child)
{
return !same_thread_group(child->real_parent, child->parent);
diff --git a/kernel/ptrace.c b/kernel/ptrace.c
index 21fec73d45d4..07ff6685ebed 100644
--- a/kernel/ptrace.c
+++ b/kernel/ptrace.c
@@ -268,9 +268,10 @@ static int ptrace_has_cap(struct user_namespace *ns, unsigned int mode)
}
/* Returns 0 on success, -errno on denial. */
-static int __ptrace_may_access(struct task_struct *task, unsigned int mode)
+int ___ptrace_may_access(struct task_struct *curr, struct task_struct *task,
+ unsigned int mode)
{
- const struct cred *cred = current_cred(), *tcred;
+ const struct cred *cred, *tcred;
struct mm_struct *mm;
kuid_t caller_uid;
kgid_t caller_gid;
@@ -290,9 +291,10 @@ static int __ptrace_may_access(struct task_struct *task, unsigned int mode)
*/
/* Don't let security modules deny introspection */
- if (same_thread_group(task, current))
+ if (same_thread_group(task, curr))
return 0;
rcu_read_lock();
+ cred = __task_cred(curr);
if (mode & PTRACE_MODE_FSCREDS) {
caller_uid = cred->fsuid;
caller_gid = cred->fsgid;
@@ -331,6 +333,11 @@ static int __ptrace_may_access(struct task_struct *task, unsigned int mode)
return security_ptrace_access_check(task, mode);
}
+static int __ptrace_may_access(struct task_struct *task, unsigned int mode)
+{
+ return ___ptrace_may_access(current, task, mode);
+}
+
bool ptrace_may_access(struct task_struct *task, unsigned int mode)
{
int err;
--
Jiri Kosina
SUSE Labs
reply other threads:[~2018-09-03 12:45 UTC|newest]
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