linux-kernel - [PATCH v2 27/28] ptrace: adapt ptrace_may_access() to always uses unmapped fsids

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Date:   Fri, 14 Feb 2020 19:35:53 +0100
From:   Christian Brauner <christian.brauner@...ntu.com>
To:     Stéphane Graber <stgraber@...ntu.com>,
        "Eric W. Biederman" <ebiederm@...ssion.com>,
        Aleksa Sarai <cyphar@...har.com>, Jann Horn <jannh@...gle.com>
Cc:     smbarber@...omium.org, Seth Forshee <seth.forshee@...onical.com>,
        Alexander Viro <viro@...iv.linux.org.uk>,
        Alexey Dobriyan <adobriyan@...il.com>,
        Serge Hallyn <serge@...lyn.com>,
        James Morris <jmorris@...ei.org>,
        Kees Cook <keescook@...omium.org>,
        Jonathan Corbet <corbet@....net>,
        Phil Estes <estesp@...il.com>, linux-kernel@...r.kernel.org,
        linux-fsdevel@...r.kernel.org,
        containers@...ts.linux-foundation.org,
        linux-security-module@...r.kernel.org, linux-api@...r.kernel.org,
        Christian Brauner <christian.brauner@...ntu.com>
Subject: [PATCH v2 27/28] ptrace: adapt ptrace_may_access() to always uses unmapped fsids

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

Cc: Jann Horn <jannh@...gle.com>
Signed-off-by: Christian Brauner <christian.brauner@...ntu.com>
---
/* v2 */
patch added
---
 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