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-rw-r--r--include/linux/seccomp.h3
-rw-r--r--include/uapi/linux/seccomp.h1
-rw-r--r--kernel/seccomp.c26
-rw-r--r--tools/testing/selftests/seccomp/seccomp_bpf.c69
4 files changed, 91 insertions, 8 deletions
diff --git a/include/linux/seccomp.h b/include/linux/seccomp.h
index ecc296c137cd..c8bef436b61d 100644
--- a/include/linux/seccomp.h
+++ b/include/linux/seccomp.h
@@ -3,7 +3,8 @@
#include <uapi/linux/seccomp.h>
-#define SECCOMP_FILTER_FLAG_MASK (SECCOMP_FILTER_FLAG_TSYNC)
+#define SECCOMP_FILTER_FLAG_MASK (SECCOMP_FILTER_FLAG_TSYNC | \
+ SECCOMP_FILTER_FLAG_LOG)
#ifdef CONFIG_SECCOMP
diff --git a/include/uapi/linux/seccomp.h b/include/uapi/linux/seccomp.h
index aaad61cc46bc..19a611d0712e 100644
--- a/include/uapi/linux/seccomp.h
+++ b/include/uapi/linux/seccomp.h
@@ -17,6 +17,7 @@
/* Valid flags for SECCOMP_SET_MODE_FILTER */
#define SECCOMP_FILTER_FLAG_TSYNC 1
+#define SECCOMP_FILTER_FLAG_LOG 2
/*
* All BPF programs must return a 32-bit value.
diff --git a/kernel/seccomp.c b/kernel/seccomp.c
index 54357e361aea..ed9fde418fc4 100644
--- a/kernel/seccomp.c
+++ b/kernel/seccomp.c
@@ -44,6 +44,7 @@
* get/put helpers should be used when accessing an instance
* outside of a lifetime-guarded section. In general, this
* is only needed for handling filters shared across tasks.
+ * @log: true if all actions except for SECCOMP_RET_ALLOW should be logged
* @prev: points to a previously installed, or inherited, filter
* @prog: the BPF program to evaluate
*
@@ -59,6 +60,7 @@
*/
struct seccomp_filter {
refcount_t usage;
+ bool log;
struct seccomp_filter *prev;
struct bpf_prog *prog;
};
@@ -452,6 +454,10 @@ static long seccomp_attach_filter(unsigned int flags,
return ret;
}
+ /* Set log flag, if present. */
+ if (flags & SECCOMP_FILTER_FLAG_LOG)
+ filter->log = true;
+
/*
* If there is an existing filter, make it the prev and don't drop its
* task reference.
@@ -532,15 +538,22 @@ static void seccomp_send_sigsys(int syscall, int reason)
static u32 seccomp_actions_logged = SECCOMP_LOG_KILL | SECCOMP_LOG_TRAP |
SECCOMP_LOG_ERRNO | SECCOMP_LOG_TRACE;
-static inline void seccomp_log(unsigned long syscall, long signr, u32 action)
+static inline void seccomp_log(unsigned long syscall, long signr, u32 action,
+ bool requested)
{
bool log = false;
switch (action) {
case SECCOMP_RET_ALLOW:
+ break;
case SECCOMP_RET_TRAP:
+ log = requested && seccomp_actions_logged & SECCOMP_LOG_TRAP;
+ break;
case SECCOMP_RET_ERRNO:
+ log = requested && seccomp_actions_logged & SECCOMP_LOG_ERRNO;
+ break;
case SECCOMP_RET_TRACE:
+ log = requested && seccomp_actions_logged & SECCOMP_LOG_TRACE;
break;
case SECCOMP_RET_KILL:
default:
@@ -548,8 +561,9 @@ static inline void seccomp_log(unsigned long syscall, long signr, u32 action)
}
/*
- * Force an audit message to be emitted when the action is RET_KILL and
- * the action is allowed to be logged by the admin.
+ * Force an audit message to be emitted when the action is RET_KILL or
+ * the FILTER_FLAG_LOG bit was set and the action is allowed to be
+ * logged by the admin.
*/
if (log)
return __audit_seccomp(syscall, signr, action);
@@ -586,7 +600,7 @@ static void __secure_computing_strict(int this_syscall)
#ifdef SECCOMP_DEBUG
dump_stack();
#endif
- seccomp_log(this_syscall, SIGKILL, SECCOMP_RET_KILL);
+ seccomp_log(this_syscall, SIGKILL, SECCOMP_RET_KILL, true);
do_exit(SIGKILL);
}
@@ -695,7 +709,7 @@ static int __seccomp_filter(int this_syscall, const struct seccomp_data *sd,
case SECCOMP_RET_KILL:
default:
- seccomp_log(this_syscall, SIGSYS, action);
+ seccomp_log(this_syscall, SIGSYS, action, true);
/* Dump core only if this is the last remaining thread. */
if (get_nr_threads(current) == 1) {
siginfo_t info;
@@ -712,7 +726,7 @@ static int __seccomp_filter(int this_syscall, const struct seccomp_data *sd,
unreachable();
skip:
- seccomp_log(this_syscall, 0, action);
+ seccomp_log(this_syscall, 0, action, match ? match->log : false);
return -1;
}
#else
diff --git a/tools/testing/selftests/seccomp/seccomp_bpf.c b/tools/testing/selftests/seccomp/seccomp_bpf.c
index abf708e09892..1c8c22ce7740 100644
--- a/tools/testing/selftests/seccomp/seccomp_bpf.c
+++ b/tools/testing/selftests/seccomp/seccomp_bpf.c
@@ -1739,6 +1739,10 @@ TEST_F_SIGNAL(TRACE_syscall, kill_after_ptrace, SIGSYS)
#define SECCOMP_FILTER_FLAG_TSYNC 1
#endif
+#ifndef SECCOMP_FILTER_FLAG_LOG
+#define SECCOMP_FILTER_FLAG_LOG 2
+#endif
+
#ifndef seccomp
int seccomp(unsigned int op, unsigned int flags, void *args)
{
@@ -1844,7 +1848,8 @@ TEST(seccomp_syscall_mode_lock)
*/
TEST(detect_seccomp_filter_flags)
{
- unsigned int flags[] = { SECCOMP_FILTER_FLAG_TSYNC };
+ unsigned int flags[] = { SECCOMP_FILTER_FLAG_TSYNC,
+ SECCOMP_FILTER_FLAG_LOG };
unsigned int flag, all_flags;
int i;
long ret;
@@ -2533,6 +2538,67 @@ TEST(syscall_restart)
_metadata->passed = 0;
}
+TEST_SIGNAL(filter_flag_log, SIGSYS)
+{
+ struct sock_filter allow_filter[] = {
+ BPF_STMT(BPF_RET|BPF_K, SECCOMP_RET_ALLOW),
+ };
+ struct sock_filter kill_filter[] = {
+ BPF_STMT(BPF_LD|BPF_W|BPF_ABS,
+ offsetof(struct seccomp_data, nr)),
+ BPF_JUMP(BPF_JMP|BPF_JEQ|BPF_K, __NR_getpid, 0, 1),
+ BPF_STMT(BPF_RET|BPF_K, SECCOMP_RET_KILL),
+ BPF_STMT(BPF_RET|BPF_K, SECCOMP_RET_ALLOW),
+ };
+ struct sock_fprog allow_prog = {
+ .len = (unsigned short)ARRAY_SIZE(allow_filter),
+ .filter = allow_filter,
+ };
+ struct sock_fprog kill_prog = {
+ .len = (unsigned short)ARRAY_SIZE(kill_filter),
+ .filter = kill_filter,
+ };
+ long ret;
+ pid_t parent = getppid();
+
+ ret = prctl(PR_SET_NO_NEW_PRIVS, 1, 0, 0, 0);
+ ASSERT_EQ(0, ret);
+
+ /* Verify that the FILTER_FLAG_LOG flag isn't accepted in strict mode */
+ ret = seccomp(SECCOMP_SET_MODE_STRICT, SECCOMP_FILTER_FLAG_LOG,
+ &allow_prog);
+ ASSERT_NE(ENOSYS, errno) {
+ TH_LOG("Kernel does not support seccomp syscall!");
+ }
+ EXPECT_NE(0, ret) {
+ TH_LOG("Kernel accepted FILTER_FLAG_LOG flag in strict mode!");
+ }
+ EXPECT_EQ(EINVAL, errno) {
+ TH_LOG("Kernel returned unexpected errno for FILTER_FLAG_LOG flag in strict mode!");
+ }
+
+ /* Verify that a simple, permissive filter can be added with no flags */
+ ret = seccomp(SECCOMP_SET_MODE_FILTER, 0, &allow_prog);
+ EXPECT_EQ(0, ret);
+
+ /* See if the same filter can be added with the FILTER_FLAG_LOG flag */
+ ret = seccomp(SECCOMP_SET_MODE_FILTER, SECCOMP_FILTER_FLAG_LOG,
+ &allow_prog);
+ ASSERT_NE(EINVAL, errno) {
+ TH_LOG("Kernel does not support the FILTER_FLAG_LOG flag!");
+ }
+ EXPECT_EQ(0, ret);
+
+ /* Ensure that the kill filter works with the FILTER_FLAG_LOG flag */
+ ret = seccomp(SECCOMP_SET_MODE_FILTER, SECCOMP_FILTER_FLAG_LOG,
+ &kill_prog);
+ EXPECT_EQ(0, ret);
+
+ EXPECT_EQ(parent, syscall(__NR_getppid));
+ /* getpid() should never return. */
+ EXPECT_EQ(0, syscall(__NR_getpid));
+}
+
TEST(get_action_avail)
{
__u32 actions[] = { SECCOMP_RET_KILL, SECCOMP_RET_TRAP,
@@ -2573,6 +2639,7 @@ TEST(get_action_avail)
* - endianness checking when appropriate
* - 64-bit arg prodding
* - arch value testing (x86 modes especially)
+ * - verify that FILTER_FLAG_LOG filters generate log messages
* - ...
*/