[PATCH] misc: fastrpc: take fl->lock when moving mmaps on interrupted invoke

[Junrui Luo <moonafterrain@outlook.com>]

When an invoke is interrupted by a signal,
wait_for_completion_interruptible() returns -ERESTARTSYS and
fastrpc_internal_invoke() moves every buffer from fl->mmaps onto
cctx->invoke_interrupted_mmaps. This list_del()/list_add_tail() walk
runs without holding fl->lock, the lock that serialises fl->mmaps in
fastrpc_req_mmap() and fastrpc_req_munmap() everywhere else.

Take fl->lock around the move, matching every other fl->mmaps accessor.

Fixes: 76e8e4ace1ed ("misc: fastrpc: Safekeep mmaps on interrupted invoke")
Reported-by: Yuhao Jiang <danisjiang@gmail.com>
Cc: stable@vger.kernel.org
Signed-off-by: Junrui Luo <moonafterrain@outlook.com>
---
 drivers/misc/fastrpc.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/drivers/misc/fastrpc.c b/drivers/misc/fastrpc.c
index 1080f9acf70a..1601c9667d0b 100644
--- a/drivers/misc/fastrpc.c
+++ b/drivers/misc/fastrpc.c
@@ -1259,10 +1259,12 @@ static int fastrpc_internal_invoke(struct fastrpc_user *fl,  u32 kernel,
 	}
 
 	if (err == -ERESTARTSYS) {
+		spin_lock(&fl->lock);
 		list_for_each_entry_safe(buf, b, &fl->mmaps, node) {
 			list_del(&buf->node);
 			list_add_tail(&buf->node, &fl->cctx->invoke_interrupted_mmaps);
 		}
+		spin_unlock(&fl->lock);
 	}
 
 	if (err)

---
base-commit: e43ffb69e0438cddd72aaa30898b4dc446f664f8
change-id: 20260602-fixes-ba3a01f66f34

Best regards,
-- 
Junrui Luo <moonafterrain@outlook.com>