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authorKees Cook <keescook@chromium.org>2022-02-07 20:21:13 -0800
committerKees Cook <keescook@chromium.org>2022-02-10 19:09:12 -0800
commit495ac3069a6235bfdf516812a2a9b256671bbdf9 (patch)
tree5af379028a8b12efb8193fee1737ea4ebe968969 /kernel
parent5c72263ef2fbe99596848f03758ae2dc593adf2c (diff)
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 <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>
Diffstat (limited to 'kernel')
-rw-r--r--kernel/seccomp.c10
1 files changed, 10 insertions, 0 deletions
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();
}