linux use MFD_NOEXEC_SEAL for shared memory

ref: https://lore.kernel.org/lkml/[email protected]/ The new MFD_NOEXEC_SEAL and MFD_EXEC flags allows application to set executable bit at creation time (memfd_create). When MFD_NOEXEC_SEAL is set, memfd is created without executable bit (mode:0666), and sealed with F_SEAL_EXEC, so it can't be chmod to be executable (mode: 0777) after creation. When MFD_EXEC flag is set, memfd is created with executable bit (mode:0777), this is the same as the old behavior of memfd_create. Signed-off-by: Rudi Heitbaum <[email protected]>
heitbaum · Aug 13, 2023 · 43a9ffe · 43a9ffe
1 parent 43bf471
commit 43a9ffe
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Showing 2 changed files with 10 additions and 3 deletions.
diff --git a/xbmc/platform/posix/utils/SharedMemory.cpp b/xbmc/platform/posix/utils/SharedMemory.cpp
@@ -15,6 +15,9 @@
 #if defined(HAVE_LINUX_MEMFD)
 #include <linux/memfd.h>
 #include <sys/syscall.h>
+#ifndef MFD_NOEXEC_SEAL
+#define MFD_NOEXEC_SEAL 0x0008U
+#endif
 #endif
 
 #include <cerrno>
@@ -63,7 +66,7 @@ CFileHandle CSharedMemory::OpenMemfd()
 #if defined(SYS_memfd_create) && defined(HAVE_LINUX_MEMFD)
   // This is specific to Linux >= 3.17, but preferred over shm_create if available
   // because it is race-free
-  int fd = syscall(SYS_memfd_create, "kodi", MFD_CLOEXEC);
+  int fd = syscall(SYS_memfd_create, "kodi", MFD_CLOEXEC | MFD_ALLOW_SEALING | MFD_NOEXEC_SEAL);
   if (fd < 0)
   {
     throw std::system_error(errno, std::generic_category(), "memfd_create");
@@ -115,4 +118,4 @@ CFileHandle CSharedMemory::OpenShm()
   unlink(tmpFilename.c_str());
 
   return fd;
-}
+}
diff --git a/xbmc/utils/UDMABufferObject.cpp b/xbmc/utils/UDMABufferObject.cpp
@@ -20,6 +20,10 @@
 
 #include "PlatformDefs.h"
 
+#ifndef MFD_NOEXEC_SEAL
+#define MFD_NOEXEC_SEAL 0x0008U
+#endif
+
 namespace
 {
 
@@ -95,7 +99,7 @@ bool CUDMABufferObject::CreateBufferObject(uint64_t size)
   // Must be rounded to the system page size
   m_size = RoundUp(size, PAGESIZE);
 
-  m_memfd = memfd_create("kodi", MFD_CLOEXEC | MFD_ALLOW_SEALING);
+  m_memfd = memfd_create("kodi", MFD_CLOEXEC | MFD_ALLOW_SEALING | MFD_NOEXEC_SEAL);
   if (m_memfd < 0)
   {
     CLog::Log(LOGERROR, "CUDMABufferObject::{} - memfd_create failed: {}", __FUNCTION__,