commit 7b1de50e3c798221481f97412a1f9d0d76c963ed
author Isaac Manjarres <isaacmanjarres@google.com> Thu Mar 06 05:56:40 2025 -0800
committer Isaac J. Manjarres <isaacmanjarres@google.com> Thu Mar 06 05:59:52 2025 -0800
tree bd93f8c83c75d52c9cb0c7a0e52e8360cf0e7f8f
parent efe2276999a344f5f96d4a038c72be752b8bce88

Revert "ashmem: Ensure all memfds have non-executable permissions by default"

This reverts commit ee7a713757314366023e855a76ff17943b6b9296.

Reason for revert: We would like to evaluate switching libcutils to
memfd against older kernels that don't support MFD_NOEXEC_SEAL, so
temporarily revert it. MFD_NOEXEC_SEAL will be brought back when
testing has concluded.

Bug: 401214539
Bug: 111903542
Change-Id: I2cf76e3545ac46a65b54889f9030ad44cb1e4d27

libcutils/ashmem-dev.cpp

diff --git a/libcutils/ashmem-dev.cpp b/libcutils/ashmem-dev.cpp
index cfc2d3a..5fbe8a1 100644
--- a/libcutils/ashmem-dev.cpp
+++ b/libcutils/ashmem-dev.cpp
@@ -114,15 +114,8 @@
     // Check if kernel support exists, otherwise fall back to ashmem.
     // This code needs to build on old API levels, so we can't use the libc
     // wrapper.
-    //
-    // MFD_NOEXEC_SEAL is used to match the semantics of the ashmem device,
-    // which did not have executable permissions. This also seals the executable
-    // permissions of the buffer (i.e. they cannot be changed by fchmod()).
-    //
-    // MFD_NOEXEC_SEAL implies MFD_ALLOW_SEALING.
-
     android::base::unique_fd fd(
-            syscall(__NR_memfd_create, "test_android_memfd", MFD_CLOEXEC | MFD_NOEXEC_SEAL));
+            syscall(__NR_memfd_create, "test_android_memfd", MFD_CLOEXEC | MFD_ALLOW_SEALING));
     if (fd == -1) {
         ALOGE("memfd_create failed: %m, no memfd support");
         return false;
@@ -290,13 +283,7 @@
 static int memfd_create_region(const char* name, size_t size) {
     // This code needs to build on old API levels, so we can't use the libc
     // wrapper.
-    //
-    // MFD_NOEXEC_SEAL to match the semantics of the ashmem device, which did
-    // not have executable permissions. This also seals the executable
-    // permissions of the buffer (i.e. they cannot be changed by fchmod()).
-    //
-    // MFD_NOEXEC_SEAL implies MFD_ALLOW_SEALING.
-    android::base::unique_fd fd(syscall(__NR_memfd_create, name, MFD_CLOEXEC | MFD_NOEXEC_SEAL));
+    android::base::unique_fd fd(syscall(__NR_memfd_create, name, MFD_CLOEXEC | MFD_ALLOW_SEALING));
 
     if (fd == -1) {
         ALOGE("memfd_create(%s, %zd) failed: %m", name, size);