diff --git a/third_party/ashmem/ashmem-dev.c b/third_party/ashmem/ashmem-dev.c
index d419c775a0d41..8a1ee6218aed6 100644
--- a/third_party/ashmem/ashmem-dev.c
+++ b/third_party/ashmem/ashmem-dev.c
@@ -118,7 +118,7 @@ static AshmemStatus ashmem_get_status(void) {
 
 /* Returns true iff the ashmem device ioctl should be used for a given fd.
  * NOTE: Try not to use fstat() when possible to avoid performance issues. */
-static int ashmem_dev_fd_check(int fd) {
+static int is_ashmem_fd(int fd) {
   if (device_api_level() <= __ANDROID_API_O_MR1__)
     return 1;
   if (ashmem_get_status() == ASHMEM_STATUS_SUPPORTED) {
@@ -188,13 +188,13 @@ static size_t ashmem_dev_get_size_region(int fd) {
 // or newer, in which case, use memfd directly instead of
 // the ASharedMemory API.
 typedef int(*ASharedMemory_createFunc)(const char*, size_t);
-typedef size_t(*ASharedMemory_getSizeFunc)(int fd);
+// ASharedMemory_setProtFunc() is typically invoked in conjunction with ASharedMemory_createFunc(),
+// so it's okay for setProt to implicitly assume the type of fd it needs to work with.
 typedef int(*ASharedMemory_setProtFunc)(int fd, int prot);
 
 // Function pointers to shared memory functions.
 typedef struct {
   ASharedMemory_createFunc create;
-  ASharedMemory_getSizeFunc getSize;
   ASharedMemory_setProtFunc setProt;
 } ASharedMemoryFuncs;
 
@@ -227,16 +227,6 @@ error:
   return ret;
 }
 
-static int memfd_get_size_region(int fd) {
-  struct stat sb;
-  if (fstat(fd, &sb) == -1) {
-    LOG_E("memfd_get_size_region(%d): fstat failed: %m", fd);
-    return -1;
-  }
-
-  return sb.st_size;
-}
-
 static int memfd_set_prot_region(int fd, int prot) {
   int seals = fcntl(fd, F_GET_SEALS);
   if (seals == -1) {
@@ -299,13 +289,10 @@ static void ashmem_init_funcs() {
     }
     funcs->create =
         (ASharedMemory_createFunc)dlsym(lib, "ASharedMemory_create");
-    funcs->getSize =
-        (ASharedMemory_getSizeFunc)dlsym(lib, "ASharedMemory_getSize");
     funcs->setProt =
         (ASharedMemory_setProtFunc)dlsym(lib, "ASharedMemory_setProt");
   } else {
     funcs->create = &ashmem_dev_create_region;
-    funcs->getSize = &ashmem_dev_get_size_region;
     funcs->setProt = &ashmem_dev_set_prot_region;
   }
 }
@@ -329,34 +316,30 @@ int ashmem_set_prot_region(int fd, int prot) {
   return ashmem_get_funcs()->setProt(fd, prot);
 }
 
+static bool is_memfd_fd(int fd) {
+  if (fcntl(fd, F_GET_SEALS, 0) == -1)
+    return false;
+  return true;
+}
+
 int ashmem_get_prot_region(int fd) {
-  if (s_use_memfd)
+  if (is_memfd_fd(fd))
     return memfd_get_prot_region(fd);
-  else if (ashmem_dev_fd_check(fd))
+
+  if (is_ashmem_fd(fd))
     return ashmem_dev_get_prot_region(fd);
-  /* There are only two practical values to return here: either
-   * PROT_READ|PROT_WRITE or just PROT_READ, so try to determine
-   * the flags by trying to mmap() the region read-write first.
-   */
-  int result = PROT_READ;
-  const size_t page_size = (size_t)sysconf(_SC_PAGESIZE);
-  void* m = mmap(NULL, page_size, PROT_READ|PROT_WRITE,
-                 MAP_SHARED, fd, 0);
-  if (m != MAP_FAILED) {
-    munmap(m, page_size);
-    result = PROT_READ|PROT_WRITE;
-  }
-  return result;
+
+  return -1;
 }
 
 int ashmem_pin_region(int fd, size_t offset, size_t len) {
- if (ashmem_dev_fd_check(fd))
+ if (is_ashmem_fd(fd))
    return ashmem_dev_pin_region(fd, offset, len);
   return ASHMEM_NOT_PURGED;
 }
 
 int ashmem_unpin_region(int fd, size_t offset, size_t len) {
-  if (ashmem_dev_fd_check(fd))
+  if (is_ashmem_fd(fd))
     return ashmem_dev_unpin_region(fd, offset, len);
   /* NOTE: It is not possible to use madvise() here because it requires a
    * memory address. This could be done in the caller though, instead of
@@ -365,11 +348,16 @@ int ashmem_unpin_region(int fd, size_t offset, size_t len) {
 }
 
 int ashmem_get_size_region(int fd) {
-  if (s_use_memfd)
-    return memfd_get_size_region(fd);
+  if (is_ashmem_fd(fd))
+    return ashmem_dev_get_size_region(fd);
 
-  /* NOTE: Original API returns an int. Avoid breaking it. */
-  return (int)ashmem_get_funcs()->getSize(fd);
+  struct stat sb;
+  if (fstat(fd, &sb) == -1) {
+    LOG_E("fstat(%d) failed: %m", fd);
+    return -1;
+  }
+
+  return sb.st_size;
 }
 
 int ashmem_device_is_supported(void) {