Commit cf237052 authored Oct 30, 2020 by Mickaël Salaün Committed by Kees Cook Nov 17, 2020

ptrace: Set PF_SUPERPRIV when checking capability



Commit 69f594a3 ("ptrace: do not audit capability check when outputing
/proc/pid/stat") replaced the use of ns_capable() with
has_ns_capability{,_noaudit}() which doesn't set PF_SUPERPRIV.

Commit 6b3ad664 ("ptrace: reintroduce usage of subjective credentials in
ptrace_has_cap()") replaced has_ns_capability{,_noaudit}() with
security_capable(), which doesn't set PF_SUPERPRIV neither.

Since commit 98f368e9 ("kernel: Add noaudit variant of ns_capable()"), a
new ns_capable_noaudit() helper is available.  Let's use it!

As a result, the signature of ptrace_has_cap() is restored to its original one.

Cc: Christian Brauner <christian.brauner@ubuntu.com>
Cc: Eric Paris <eparis@redhat.com>
Cc: Jann Horn <jannh@google.com>
Cc: Kees Cook <keescook@chromium.org>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Serge E. Hallyn <serge@hallyn.com>
Cc: Tyler Hicks <tyhicks@linux.microsoft.com>
Cc: stable@vger.kernel.org
Fixes: 6b3ad664 ("ptrace: reintroduce usage of subjective credentials in ptrace_has_cap()")
Fixes: 69f594a3 ("ptrace: do not audit capability check when outputing /proc/pid/stat")
Signed-off-by: Mickaël Salaün <mic@linux.microsoft.com>
Reviewed-by: Jann Horn <jannh@google.com>
Signed-off-by: Kees Cook <keescook@chromium.org>
Link: https://lore.kernel.org/r/20201030123849.770769-2-mic@digikod.net

parent 09162bc3

kernel/ptrace.c

+5 −11

Original line number	Diff line number	Diff line
		@@ -264,17 +264,11 @@ static int ptrace_check_attach(struct task_struct *child, bool ignore_state)
		return ret;
		}

		static bool ptrace_has_cap(const struct cred cred, struct user_namespace ns,
		unsigned int mode)
		static bool ptrace_has_cap(struct user_namespace *ns, unsigned int mode)
		{
		int ret;

		if (mode & PTRACE_MODE_NOAUDIT)
		ret = security_capable(cred, ns, CAP_SYS_PTRACE, CAP_OPT_NOAUDIT);
		else
		ret = security_capable(cred, ns, CAP_SYS_PTRACE, CAP_OPT_NONE);

		return ret == 0;
		return ns_capable_noaudit(ns, CAP_SYS_PTRACE);
		return ns_capable(ns, CAP_SYS_PTRACE);
		}

		/* Returns 0 on success, -errno on denial. */
		@@ -326,7 +320,7 @@ static int __ptrace_may_access(struct task_struct *task, unsigned int mode)
		gid_eq(caller_gid, tcred->sgid) &&
		gid_eq(caller_gid, tcred->gid))
		goto ok;
		if (ptrace_has_cap(cred, tcred->user_ns, mode))
		if (ptrace_has_cap(tcred->user_ns, mode))
		goto ok;
		rcu_read_unlock();
		return -EPERM;
		@@ -345,7 +339,7 @@ ok:
		mm = task->mm;
		if (mm &&
		((get_dumpable(mm) != SUID_DUMP_USER) &&
		!ptrace_has_cap(cred, mm->user_ns, mode)))
		!ptrace_has_cap(mm->user_ns, mode)))
		return -EPERM;

		return security_ptrace_access_check(task, mode);

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