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seccomp: Invalidate seccomp mode to catch death failures

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commit 495ac3069a6235bfdf516812a2a9b256671bbdf9 upstream.

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: 8112c4f140 ("seccomp: remove 2-phase API")
Cc: stable@vger.kernel.org
Signed-off-by: Kees Cook <keescook@chromium.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Kees Cook 2022-02-07 20:21:13 -08:00 committed by Greg Kroah-Hartman
parent a3769078c9
commit 1e30073c0e
1 changed files with 10 additions and 0 deletions
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10
kernel/seccomp.c
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@ -28,6 +28,9 @@
#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
@ -706,6 +709,7 @@ 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);
}
@ -892,6 +896,7 @@ 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_PROCESS ||
@ -944,6 +949,11 @@ 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();
}