seccomp: Fix setting loaded filter count during TSYNC

The desired behavior is to set the caller's filter count to thread's.
This value is reported via /proc, so this fixes the inaccurate count
exposed to userspace; it is not used for reference counting, etc.

Signed-off-by: Hsuan-Chi Kuo <hsuanchikuo@gmail.com>
Link: https://lore.kernel.org/r/20210304233708.420597-1-hsuanchikuo@gmail.com
Co-developed-by: Wiktor Garbacz <wiktorg@google.com>
Signed-off-by: Wiktor Garbacz <wiktorg@google.com>
Link: https://lore.kernel.org/lkml/20210810125158.329849-1-wiktorg@google.com
Signed-off-by: Kees Cook <keescook@chromium.org>
Cc: stable@vger.kernel.org
Fixes: c818c03b661c ("seccomp: Report number of loaded filters in /proc/$pid/status")

diff --git a/kernel/seccomp.c b/kernel/seccomp.c
index 057e17f3215d5633fc18df103fae36702a63bba4..6469eca8078ca01eb3e0407d741964a25e88d2d1 100644 (file)
--- a/kernel/seccomp.c
+++ b/kernel/seccomp.c
@@ -602,7 +602,7 @@ static inline void seccomp_sync_threads(unsigned long flags)
                smp_store_release(&thread->seccomp.filter,
                                  caller->seccomp.filter);
                atomic_set(&thread->seccomp.filter_count,
-                          atomic_read(&thread->seccomp.filter_count));
+                          atomic_read(&caller->seccomp.filter_count));
 
                /*
                 * Don't let an unprivileged task work around