dma-buf/sw-sync: always taint the kernel when sw-sync is used

The SW-sync functionality should only be used for testing and debugging
since it is inherently unsave.

Signed-off-by: Christian König <christian.koenig@amd.com>
Acked-by: Sumit Semwal <sumit.semwal@linaro.org>
Link: https://lore.kernel.org/r/20251120150018.27385-3-christian.koenig@amd.com

diff --git a/drivers/dma-buf/sw_sync.c b/drivers/dma-buf/sw_sync.c
index 3c20f1d31cf542ffba31d8808d933f9aeb0cf249..6f09d13be6b67c1ea617543dd1ab0f8aef0217a0 100644 (file)
--- a/drivers/dma-buf/sw_sync.c
+++ b/drivers/dma-buf/sw_sync.c
@@ -8,6 +8,7 @@
 #include <linux/file.h>
 #include <linux/fs.h>
 #include <linux/uaccess.h>
+#include <linux/panic.h>
 #include <linux/slab.h>
 #include <linux/sync_file.h>
 
@@ -349,6 +350,9 @@ static long sw_sync_ioctl_create_fence(struct sync_timeline *obj,
        struct sync_file *sync_file;
        struct sw_sync_create_fence_data data;
 
+       /* SW sync fence are inherently unsafe and can deadlock the kernel */
+       add_taint(TAINT_SOFTLOCKUP, LOCKDEP_STILL_OK);
+
        if (fd < 0)
                return fd;