[PATCH v4 7/7] rust_binder: reject mremap()

[Carlos Llamas <cmllamas@google.com>]

Binder does not support mremap() as it caches the mapping address in
Inner::vma_addr. Moving the mapping breaks the IPC communication for the
process and can temporarily leak pages during a shrinker reclaim.

Fix this by explicitly rejecting the .mremap() operation.

Cc: stable@vger.kernel.org
Fixes: eafedbc7c050 ("rust_binder: add Rust Binder driver")
Reported-by: Sashiko <sashiko-bot@kernel.org>
Closes: https://sashiko.dev/#/patchset/20260813193433.3318288-1-surenb@google.com?part=2
Signed-off-by: Carlos Llamas <cmllamas@google.com>
---
 drivers/android/binder/page_range.rs | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/drivers/android/binder/page_range.rs b/drivers/android/binder/page_range.rs
index d260b009c184..c6247ba03313 100644
--- a/drivers/android/binder/page_range.rs
+++ b/drivers/android/binder/page_range.rs
@@ -148,9 +148,14 @@ pub(crate) struct ShrinkablePageRange {
     EINVAL.to_errno()
 }
 
+unsafe extern "C" fn binder_mremap(_: *mut bindings::vm_area_struct) -> c_int {
+    EINVAL.to_errno()
+}
+
 static BINDER_VM_OPS: AssertSync<bindings::vm_operations_struct> = {
     let ops = bindings::vm_operations_struct {
         may_split: Some(binder_vma_may_split),
+        mremap: Some(binder_mremap),
         ..pin_init::zeroed()
     };
     AssertSync(ops)
-- 
2.55.0.966.g6673acef38-goog