linux-kernel - [PATCH 5.11 43/44] tomoyo: recognize kernel threads correctly

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Message-Id: <20210308122720.655560259@linuxfoundation.org>
Date:   Mon,  8 Mar 2021 13:35:21 +0100
From:   gregkh@...uxfoundation.org
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org,
        Tetsuo Handa <penguin-kernel@...ove.SAKURA.ne.jp>
Subject: [PATCH 5.11 43/44] tomoyo: recognize kernel threads correctly

From: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

From: Tetsuo Handa <penguin-kernel@...ove.SAKURA.ne.jp>

commit 9c83465f3245c2faa82ffeb7016f40f02bfaa0ad upstream.

Commit db68ce10c4f0a27c ("new helper: uaccess_kernel()") replaced
segment_eq(get_fs(), KERNEL_DS) with uaccess_kernel(). But the correct
method for tomoyo to check whether current is a kernel thread in order
to assume that kernel threads are privileged for socket operations was
(current->flags & PF_KTHREAD). Now that uaccess_kernel() became 0 on x86,
tomoyo has to fix this problem. Do like commit 942cb357ae7d9249 ("Smack:
Handle io_uring kernel thread privileges") does.

Signed-off-by: Tetsuo Handa <penguin-kernel@...ove.SAKURA.ne.jp>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
---
 security/tomoyo/network.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

--- a/security/tomoyo/network.c
+++ b/security/tomoyo/network.c
@@ -613,7 +613,7 @@ static int tomoyo_check_unix_address(str
 static bool tomoyo_kernel_service(void)
 {
 	/* Nothing to do if I am a kernel service. */
-	return uaccess_kernel();
+	return (current->flags & (PF_KTHREAD | PF_IO_WORKER)) == PF_KTHREAD;
 }

 /**