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[Qemu-devel] [PULL v1 15/32] tpm-passthrough: workaround a possible race
From: |
Stefan Berger |
Subject: |
[Qemu-devel] [PULL v1 15/32] tpm-passthrough: workaround a possible race |
Date: |
Sat, 16 Dec 2017 12:41:32 -0500 |
From: Marc-André Lureau <address@hidden>
The TPM backend processing thread has common shared variable race
issues. (they should not be so easy to reach since guest interaction
with the device is slow compared to host emulation)
An obvious one is setting op_cancelled from device thread after
calling write(cancel_fd). The backend thread may return before the
device thread has set the variable. Instead set it before
cancellation. Even if the write() failed, the end result is command
get possibly cancelled (even if cancellation came from external
sources it doesn't matter much).
It's worth to consider removing the backend processing thread for now.
Signed-off-by: Marc-André Lureau <address@hidden>
Reviewed-by: Stefan Berger <address@hidden>
Signed-off-by: Stefan Berger <address@hidden>
---
hw/tpm/tpm_passthrough.c | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)
diff --git a/hw/tpm/tpm_passthrough.c b/hw/tpm/tpm_passthrough.c
index 788be38..73554aa 100644
--- a/hw/tpm/tpm_passthrough.c
+++ b/hw/tpm/tpm_passthrough.c
@@ -89,6 +89,7 @@ static int tpm_passthrough_unix_tx_bufs(TPMPassthruState
*tpm_pt,
bool is_selftest;
const struct tpm_resp_hdr *hdr;
+ /* FIXME: protect shared variables or use other sync mechanism */
tpm_pt->tpm_op_canceled = false;
tpm_pt->tpm_executing = true;
*selftest_done = false;
@@ -178,12 +179,11 @@ static void tpm_passthrough_cancel_cmd(TPMBackend *tb)
*/
if (tpm_pt->tpm_executing) {
if (tpm_pt->cancel_fd >= 0) {
+ tpm_pt->tpm_op_canceled = true;
n = write(tpm_pt->cancel_fd, "-", 1);
if (n != 1) {
error_report("Canceling TPM command failed: %s",
strerror(errno));
- } else {
- tpm_pt->tpm_op_canceled = true;
}
} else {
error_report("Cannot cancel TPM command due to missing "
--
2.5.5
- [Qemu-devel] [PULL v1 07/32] tpm-be: ask model to the TPM interface, (continued)
- [Qemu-devel] [PULL v1 07/32] tpm-be: ask model to the TPM interface, Stefan Berger, 2017/12/16
- [Qemu-devel] [PULL v1 06/32] tpm-be: report error instead of front-end, Stefan Berger, 2017/12/16
- [Qemu-devel] [PULL v1 05/32] tpm-be: call request_completed() out of thread, Stefan Berger, 2017/12/16
- [Qemu-devel] [PULL v1 04/32] tpm-tis: no longer expose TPMState, Stefan Berger, 2017/12/16
- [Qemu-devel] [PULL v1 08/32] tpm: remove unused opened code, Stefan Berger, 2017/12/16
- [Qemu-devel] [PULL v1 13/32] tpm-passthrough: make it safer to destroy after creation, Stefan Berger, 2017/12/16
- [Qemu-devel] [PULL v1 11/32] tpm-passthrough: pass TPMPassthruState to handle_device_opts, Stefan Berger, 2017/12/16
- [Qemu-devel] [PULL v1 10/32] tpm-be: update optional function pointers, Stefan Berger, 2017/12/16
- [Qemu-devel] [PULL v1 09/32] tpm-passthrough: don't save guessed cancel_path in options, Stefan Berger, 2017/12/16
- [Qemu-devel] [PULL v1 12/32] tpm-backend: move set 'id' to common code, Stefan Berger, 2017/12/16
- [Qemu-devel] [PULL v1 15/32] tpm-passthrough: workaround a possible race,
Stefan Berger <=
- [Qemu-devel] [PULL v1 14/32] tpm-passthrough: simplify create(), Stefan Berger, 2017/12/16
- [Qemu-devel] [PULL v1 17/32] tpm: rename qemu_find_tpm() -> qemu_find_tpm_be(), Stefan Berger, 2017/12/16
- [Qemu-devel] [PULL v1 18/32] tpm: lookup the the TPM interface instead of TIS device, Stefan Berger, 2017/12/16
- [Qemu-devel] [PULL v1 16/32] tpm-tis: simplify header inclusion, Stefan Berger, 2017/12/16
- [Qemu-devel] [PULL v1 20/32] tpm: add tpm_cmd_get_size() to tpm_util, Stefan Berger, 2017/12/16
- [Qemu-devel] [PULL v1 19/32] tpm: add TPM interface to lookup TPM version, Stefan Berger, 2017/12/16
- [Qemu-devel] [PULL v1 21/32] acpi: change TPM TIS data conditions, Stefan Berger, 2017/12/16
- [Qemu-devel] [PULL v1 22/32] tpm-emulator: add a FIXME comment about blocking cancel, Stefan Berger, 2017/12/16
- [Qemu-devel] [PULL v1 23/32] tpm-tis: remove redundant 'tpm_tis:' in error messages, Stefan Berger, 2017/12/16
- [Qemu-devel] [PULL v1 25/32] qdev: add DEFINE_PROP_TPMBE, Stefan Berger, 2017/12/16