[PATCH v3 21/25] ptrace: adapt ptrace_may_access() to always uses unmapped fsids

From: Christian Brauner <christian.brauner@ubuntu.com>
To: "Stéphane Graber" <stgraber@ubuntu.com>,
	"Eric W. Biederman" <ebiederm@xmission.com>,
	"Aleksa Sarai" <cyphar@cyphar.com>,
	"Jann Horn" <jannh@google.com>
Cc: smbarber@chromium.org, Seth Forshee <seth.forshee@canonical.com>,
	Alexander Viro <viro@zeniv.linux.org.uk>,
	Alexey Dobriyan <adobriyan@gmail.com>,
	Serge Hallyn <serge@hallyn.com>, James Morris <jmorris@namei.org>,
	Kees Cook <keescook@chromium.org>,
	Jonathan Corbet <corbet@lwn.net>, Phil Estes <estesp@gmail.com>,
	linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org,
	containers@lists.linux-foundation.org,
	linux-security-module@vger.kernel.org, linux-api@vger.kernel.org,
	Christian Brauner <christian.brauner@ubuntu.com>
Subject: [PATCH v3 21/25] ptrace: adapt ptrace_may_access() to always uses unmapped fsids
Date: Tue, 18 Feb 2020 15:34:07 +0100	[thread overview]
Message-ID: <20200218143411.2389182-22-christian.brauner@ubuntu.com> (raw)
In-Reply-To: <20200218143411.2389182-1-christian.brauner@ubuntu.com>

ptrace_may_access() with PTRACE_MODE_FSCREDS is only used with proc and proc
wants to use the unmapped fsids.

Suggested-by: Jann Horn <jannh@google.com>
Signed-off-by: Christian Brauner <christian.brauner@ubuntu.com>
---
/* v2 */
patch added

/* v3 */
unchanged
---
 kernel/ptrace.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/kernel/ptrace.c b/kernel/ptrace.c
index 43d6179508d6..3734713cc0dd 100644
--- a/kernel/ptrace.c
+++ b/kernel/ptrace.c
@@ -304,8 +304,8 @@ static int __ptrace_may_access(struct task_struct *task, unsigned int mode)
 		return 0;
 	rcu_read_lock();
 	if (mode & PTRACE_MODE_FSCREDS) {
-		caller_uid = cred->fsuid;
-		caller_gid = cred->fsgid;
+		caller_uid = cred->kfsuid;
+		caller_gid = cred->kfsgid;
 	} else {
 		/*
 		 * Using the euid would make more sense here, but something
-- 
2.25.0

