@@ -1160,12 +1160,6 @@ static int __seccomp_filter(int this_syscall, const struct seccomp_data *sd,
int data;
struct seccomp_data sd_local;
- /*
- * Make sure that any changes to mode from another thread have
- * been seen after SYSCALL_WORK_SECCOMP was seen.
- */
- smp_rmb();
-
if (!sd) {
populate_seccomp_data(&sd_local);
sd = &sd_local;
@@ -1291,7 +1285,6 @@ static int __seccomp_filter(int this_syscall, const struct seccomp_data *sd,
int __secure_computing(const struct seccomp_data *sd)
{
- int mode = current->seccomp.mode;
int this_syscall;
if (IS_ENABLED(CONFIG_CHECKPOINT_RESTORE) &&
@@ -1301,7 +1294,13 @@ int __secure_computing(const struct seccomp_data *sd)
this_syscall = sd ? sd->nr :
syscall_get_nr(current, current_pt_regs());
- switch (mode) {
+ /*
+ * Make sure that any changes to mode from another thread have
+ * been seen after SYSCALL_WORK_SECCOMP was seen.
+ */
+ smp_rmb();
+
+ switch (current->seccomp.mode) {
case SECCOMP_MODE_STRICT:
__secure_computing_strict(this_syscall); /* may call do_exit */
return 0;
As Kees haved accepted the v2 patch at a381b70a1 which just replaced rmb() with smp_rmb(), this patch will base on that and just adjust the smp_rmb() to the correct position. As the original comment shown (and indeed it should be): /* * Make sure that any changes to mode from another thread have * been seen after SYSCALL_WORK_SECCOMP was seen. */ the smp_rmb() should be put between reading SYSCALL_WORK_SECCOMP and reading seccomp.mode to make sure that any changes to mode from another thread have been seen after SYSCALL_WORK_SECCOMP was seen, for TSYNC situation. However, it is misplaced between reading seccomp.mode and seccomp->filter. This issue seems to be misintroduced at 13aa72f0fd0a9f98a41cefb662487269e2f1ad65 which aims to refactor the filter callback and the API. So let's just adjust the smp_rmb() to the correct position. A next optimization patch will be provided if this ajustment is appropriate. ref:https://lore.kernel.org/lkml/1614157085-18952-1-git-send-email-wanghongzhe@huawei.com/ v2 -> v3: - move the smp_rmb() to the correct position v1 -> v2: - only replace rmb() with smp_rmb() - provide the performance test number RFC -> v1: - replace rmb() with smp_rmb() - move the smp_rmb() logic to the middle between TIF_SECCOMP and mode Signed-off-by: wanghongzhe <wanghongzhe@huawei.com> --- kernel/seccomp.c | 15 +++++++-------- 1 file changed, 7 insertions(+), 8 deletions(-)