From 1c98ae4fddf13ff3b55b3edac682375b07fe1f58 Mon Sep 17 00:00:00 2001 From: Mattias Nissler Date: Fri, 11 May 2018 14:16:46 +0200 Subject: tpm_lite: Set O_CLOEXEC when opening TPM device. This sets O_CLOEXEC when opening the TPM device to make sure the file descriptor isn't shared across processes. The TPM character device exposes the raw communication channel to send/receive commands to/from the TPM. The TPM is not designed for concurrent access by multiple users and the kernel driver already returns EBUSY on open when a different process has already opened it. Consequently, it only makes sense to have the /dev/tpm0 file descriptor be closed automatically on exec(). None of the callers I'm aware of need to share the TPM file descriptor across processes, and mount-encrypted has some ad-hoc code to close the descriptor when it does fork+exec to spawn a helper. The existing code isn't consistent and comprehensive (mount-encrypted spawns other helpers where it forgets to close the file descriptor), so the plan is to set O_CLOEXEC and remove the ad-hoc code. BRANCH=None BUG=None TEST=Compiles, passes tests, image boots. Change-Id: Ia6e73fb12e8f2ed8fe99b4c53ea6eb8cda4a21f5 Reviewed-on: https://chromium-review.googlesource.com/1055569 Commit-Ready: Mattias Nissler Tested-by: Mattias Nissler Reviewed-by: Andrey Pronin --- firmware/stub/tpm_lite_stub.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/firmware/stub/tpm_lite_stub.c b/firmware/stub/tpm_lite_stub.c index 4c846312..004eeaf5 100644 --- a/firmware/stub/tpm_lite_stub.c +++ b/firmware/stub/tpm_lite_stub.c @@ -172,7 +172,7 @@ VbError_t VbExTpmOpen(void) /* Retry TPM opens on EBUSY failures. */ for (retries = 0; retries < OPEN_RETRY_MAX_NUM; ++ retries) { errno = 0; - tpm_fd = open(device_path, O_RDWR); + tpm_fd = open(device_path, O_RDWR | O_CLOEXEC); saved_errno = errno; if (tpm_fd >= 0) return VBERROR_SUCCESS; -- cgit v1.2.1