From: Kees Cook <keescook@chromium.org>
To: "Eric W. Biederman" <ebiederm@xmission.com>
Cc: "Kees Cook" <keescook@chromium.org>,
"Andy Lutomirski" <luto@amacapital.net>,
"Will Drewry" <wad@chromium.org>,
stable@vger.kernel.org, "Robert Święcki" <robert@swiecki.net>,
linux-kernel@vger.kernel.org, linux-hardening@vger.kernel.org
Subject: [PATCH 2/3] seccomp: Invalidate seccomp mode to catch death failures
Date: Wed, 9 Feb 2022 18:53:20 -0800 [thread overview]
Message-ID: <20220210025321.787113-3-keescook@chromium.org> (raw)
In-Reply-To: <20220210025321.787113-1-keescook@chromium.org>
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 <luto@amacapital.net>
Cc: Will Drewry <wad@chromium.org>
Fixes: 8112c4f140fa ("seccomp: remove 2-phase API")
Cc: stable@vger.kernel.org
Signed-off-by: Kees Cook <keescook@chromium.org>
---
kernel/seccomp.c | 10 ++++++++++
1 file changed, 10 insertions(+)
diff --git a/kernel/seccomp.c b/kernel/seccomp.c
index 4d8f44a17727..db10e73d06e0 100644
--- a/kernel/seccomp.c
+++ b/kernel/seccomp.c
@@ -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();
}
--
2.30.2
next prev parent reply other threads:[~2022-02-10 2:53 UTC|newest]
Thread overview: 24+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-02-10 2:53 [PATCH 0/3] signal: HANDLER_EXIT should clear SIGNAL_UNKILLABLE Kees Cook
2022-02-10 2:53 ` [PATCH 1/3] " Kees Cook
2022-02-10 16:18 ` Jann Horn
2022-02-10 17:37 ` Kees Cook
2022-02-10 18:01 ` Jann Horn
2022-02-10 18:12 ` Eric W. Biederman
2022-02-10 21:09 ` Kees Cook
2022-02-11 20:15 ` Jann Horn
2022-02-10 18:16 ` Eric W. Biederman
2022-02-10 2:53 ` Kees Cook [this message]
2022-02-10 2:53 ` [PATCH 3/3] samples/seccomp: Adjust sample to also provide kill option Kees Cook
2022-02-10 18:17 ` [PATCH 0/3] signal: HANDLER_EXIT should clear SIGNAL_UNKILLABLE Eric W. Biederman
2022-02-10 18:41 ` Kees Cook
2022-02-10 18:58 ` Eric W. Biederman
2022-02-10 20:43 ` Kees Cook
2022-02-10 22:48 ` Eric W. Biederman
2022-02-11 1:26 ` Kees Cook
2022-02-11 1:47 ` Eric W. Biederman
2022-02-11 2:53 ` Kees Cook
2022-02-11 12:54 ` Robert Święcki
2022-02-11 17:46 ` Eric W. Biederman
2022-02-11 18:57 ` Robert Święcki
2022-02-11 20:01 ` Kees Cook
2022-02-11 19:58 ` Kees Cook
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