ashmem: Test for ASHMEM_GET_SIZE for ashmem-memfd compatibility
ASHMEM_SET_SIZE will return an error in the ashmem-memfd compatibility
logic, but ASHMEM_GET_SIZE will work as expected, so exercise that ioctl
command when testing for ashmem-memfd compatibility.
Bug: 111903542
Change-Id: I3a042063082fdf6d8d836ad9b37becc318e8d89d
Signed-off-by: Isaac J. Manjarres <isaacmanjarres@google.com>
diff --git a/libcutils/ashmem-dev.cpp b/libcutils/ashmem-dev.cpp
index adf7e37..768db81 100644
--- a/libcutils/ashmem-dev.cpp
+++ b/libcutils/ashmem-dev.cpp
@@ -120,8 +120,11 @@
// permissions of the buffer (i.e. they cannot be changed by fchmod()).
//
// MFD_NOEXEC_SEAL implies MFD_ALLOW_SEALING.
+ const char *test_buf_name = "test_android_memfd";
+ size_t buf_size = getpagesize();
+
android::base::unique_fd fd(
- syscall(__NR_memfd_create, "test_android_memfd", MFD_CLOEXEC | MFD_NOEXEC_SEAL));
+ syscall(__NR_memfd_create, test_buf_name, MFD_CLOEXEC | MFD_NOEXEC_SEAL));
if (fd == -1) {
ALOGE("memfd_create failed: %m, no memfd support");
return false;
@@ -132,13 +135,20 @@
return false;
}
+ if (ftruncate(fd, buf_size) == -1) {
+ ALOGE("ftruncate(%s, %zd) failed to set memfd buffer size: %m, no memfd support",
+ test_buf_name, buf_size);
+ return false;
+ }
+
/*
* Ensure that the kernel supports ashmem ioctl commands on memfds. If not,
* fall back to using ashmem.
*/
- if (TEMP_FAILURE_RETRY(ioctl(fd, ASHMEM_SET_SIZE, getpagesize())) < 0) {
- ALOGE("ioctl(ASHMEM_SET_SIZE, %d) failed: %m, no ashmem-memfd compat support",
- getpagesize());
+ int ashmem_size = TEMP_FAILURE_RETRY(ioctl(fd, ASHMEM_GET_SIZE, 0));
+ if (ashmem_size != static_cast<int>(buf_size)) {
+ ALOGE("ioctl(ASHMEM_GET_SIZE): %d != buf_size: %zd , no ashmem-memfd compat support",
+ ashmem_size, buf_size);
return false;
}