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FAILED: patch "[PATCH] seccomp: Invalidate seccomp mode to catch death failures" failed to apply to 4.9-stable tree

PATCH [email protected] 1 participant 1 message Feb 13, 2022

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The patch below does not apply to the 4.9-stable tree.
If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to <[email protected]>.

thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

From 495ac3069a6235bfdf516812a2a9b256671bbdf9 Mon Sep 17 00:00:00 2001
From: Kees Cook <[email protected]>
Date: Mon, 7 Feb 2022 20:21:13 -0800
Subject: [PATCH] seccomp: Invalidate seccomp mode to catch death failures

If seccomp tries to kill a process, it should never see that process again. To enforce this proactively, switch the mode to something impossible. If encountered: WARN, reject all syscalls, and attempt to kill the process again even harder.

Cc Andy Lutomirski <[email protected]>
Cc Will Drewry <[email protected]>
Fixes 8112c4f140fa ("seccomp: remove 2-phase API")
Cc [email protected]
Signed-off-by Kees Cook <[email protected]>
kernel/seccomp.c +10 -0
index 4d8f44a17727..db10e73d06e0 100644
@@ -29,6 +29,9 @@
 #include <linux/syscalls.h>
 #include <linux/sysctl.h>
 
+/* Not exposed in headers: strictly internal use only. */
+#define SECCOMP_MODE_DEAD	(SECCOMP_MODE_FILTER + 1)
+
 #ifdef CONFIG_HAVE_ARCH_SECCOMP_FILTER
 #include <asm/syscall.h>
 #endif

@@ -1010,6 +1013,7 @@ static void __secure_computing_strict(int this_syscall)
 #ifdef SECCOMP_DEBUG
 	dump_stack();
 #endif
+	current->seccomp.mode = SECCOMP_MODE_DEAD;
 	seccomp_log(this_syscall, SIGKILL, SECCOMP_RET_KILL_THREAD, true);
 	do_exit(SIGKILL);
 }

@@ -1261,6 +1265,7 @@ static int __seccomp_filter(int this_syscall, const struct seccomp_data *sd,
 	case SECCOMP_RET_KILL_THREAD:
 	case SECCOMP_RET_KILL_PROCESS:
 	default:
+		current->seccomp.mode = SECCOMP_MODE_DEAD;
 		seccomp_log(this_syscall, SIGSYS, action, true);
 		/* Dump core only if this is the last remaining thread. */
 		if (action != SECCOMP_RET_KILL_THREAD ||

@@ -1309,6 +1314,11 @@ int __secure_computing(const struct seccomp_data *sd)
 		return 0;
 	case SECCOMP_MODE_FILTER:
 		return __seccomp_filter(this_syscall, sd, false);
+	/* Surviving SECCOMP_RET_KILL_* must be proactively impossible. */
+	case SECCOMP_MODE_DEAD:
+		WARN_ON_ONCE(1);
+		do_exit(SIGKILL);
+		return -1;
 	default:
 		BUG();
 	}