Merge cherrypicks of ['googleplex-android-review.googlesource.com/24776869']... (a915b479) · Commits · e / os / android_system_core

libcutils/ashmem-dev.cpp

+25 −4

Original line number	Diff line number	Diff line
		@@ -349,6 +349,12 @@ static int memfd_create_region(const char* name, size_t size) {
		return -1;
		}

		// forbid size changes to match ashmem behaviour
		if (fcntl(fd, F_ADD_SEALS, F_SEAL_GROW \| F_SEAL_SHRINK) == -1) {
		ALOGE("memfd_create(%s, %zd) F_ADD_SEALS failed: %m", name, size);
		return -1;
		}

		if (debug_log) {
		ALOGE("memfd_create(%s, %zd) success. fd=%d\n", name, size, fd.get());
		}
		@@ -400,14 +406,29 @@ error:
		}

		static int memfd_set_prot_region(int fd, int prot) {
		/* Only proceed if an fd needs to be write-protected */
		int seals = fcntl(fd, F_GET_SEALS);
		if (seals == -1) {
		ALOGE("memfd_set_prot_region(%d, %d): F_GET_SEALS failed: %s\n", fd, prot, strerror(errno));
		return -1;
		}

		if (prot & PROT_WRITE) {
		/* Now we want the buffer to be read-write, let's check if the buffer
		* has been previously marked as read-only before, if so return error
		*/
		if (seals & F_SEAL_FUTURE_WRITE) {
		ALOGE("memfd_set_prot_region(%d, %d): region is write protected\n", fd, prot);
		errno = EINVAL; // inline with ashmem error code, if already in
		// read-only mode
		return -1;
		}
		return 0;
		}

		if (fcntl(fd, F_ADD_SEALS, F_SEAL_FUTURE_WRITE) == -1) {
		ALOGE("memfd_set_prot_region(%d, %d): F_SEAL_FUTURE_WRITE seal failed: %s\n", fd, prot,
		strerror(errno));
		/* We would only allow read-only for any future file operations */
		if (fcntl(fd, F_ADD_SEALS, F_SEAL_FUTURE_WRITE \| F_SEAL_SEAL) == -1) {
		ALOGE("memfd_set_prot_region(%d, %d): F_SEAL_FUTURE_WRITE \| F_SEAL_SEAL seal failed: %s\n",
		fd, prot, strerror(errno));
		return -1;
		}