Datagram: add mutex to protect data buffers

The driver is thread safe but the buffers are shared across threads.
Adding mutexes around the use of the buffers prevents race conditions
that were causing transaction failures.

Bug: 111653201
Test: try and race transactions, they no longer fail
Change-Id: If58f203eb31075174e5d15eaaea4405eb5082342

1 files changed, 31 insertions, 4 deletions

diff --git a/citadel/libnos_datagram/citadel.c b/citadel/libnos_datagram/citadel.c
index cea0a42..f2ba9ba 100644
--- a/citadel/libnos_datagram/citadel.c
+++ b/citadel/libnos_datagram/citadel.c
@@ -24,6 +24,7 @@
 #include <getopt.h>
 #include <linux/types.h>
 #include <poll.h>
+#include <pthread.h>
 #include <stdarg.h>
 #include <stdint.h>
 #include <stdio.h>
@@ -47,6 +48,7 @@ struct citadel_ioc_tpm_datagram {
 
 #define DEV_CITADEL "/dev/citadel0"
 
+static pthread_mutex_t in_buf_mutex = PTHREAD_MUTEX_INITIALIZER;
 static uint8_t in_buf[MAX_DEVICE_TRANSFER];
 static int read_datagram(void *ctx, uint32_t command, uint8_t *buf, uint32_t len) {
     struct citadel_ioc_tpm_datagram dg = {
@@ -74,17 +76,30 @@ static int read_datagram(void *ctx, uint32_t command, uint8_t *buf, uint32_t len
         return -E2BIG;
     }
 
+    /* Lock the in buffer while it is used for this transaction */
+    if (pthread_mutex_lock(&in_buf_mutex) != 0) {
+        ALOGE("%s: failed to lock in_buf_mutex: %s", __func__, strerror(errno));
+        return -errno;
+    }
+
     ret = ioctl(fd, CITADEL_IOC_TPM_DATAGRAM, &dg);
     if (ret < 0) {
         ALOGE("can't send spi message: %s", strerror(errno));
-        return -errno;
+        ret = -errno;
+        goto out;
     }
 
     memcpy(buf, in_buf, len);
 
-    return 0;
+out:
+    if (pthread_mutex_unlock(&in_buf_mutex) != 0) {
+        ALOGE("%s: failed to unlock in_buf_mutex: %s", __func__, strerror(errno));
+        ret = -errno;
+    }
+    return ret;
 }
 
+static pthread_mutex_t out_buf_mutex = PTHREAD_MUTEX_INITIALIZER;
 static uint8_t out_buf[MAX_DEVICE_TRANSFER];
 static int write_datagram(void *ctx, uint32_t command, const uint8_t *buf, uint32_t len) {
     struct citadel_ioc_tpm_datagram dg = {
@@ -111,15 +126,27 @@ static int write_datagram(void *ctx, uint32_t command, const uint8_t *buf, uint3
         return -E2BIG;
     }
 
+    /* Lock the out buffer while it is used for this transaction */
+    if (pthread_mutex_lock(&out_buf_mutex) != 0) {
+        ALOGE("%s: failed to lock out_buf_mutex: %s", __func__, strerror(errno));
+        return -errno;
+    }
+
     memcpy(out_buf, buf, len);
 
     ret = ioctl(fd, CITADEL_IOC_TPM_DATAGRAM, &dg);
     if (ret < 0) {
         ALOGE("can't send spi message: %s", strerror(errno));
-        return -errno;
+        ret = -errno;
+        goto out;
     }
 
-    return 0;
+out:
+    if (pthread_mutex_unlock(&out_buf_mutex) != 0) {
+        ALOGE("%s: failed to unlock out_buf_mutex: %s", __func__, strerror(errno));
+        ret = -errno;
+    }
+    return ret;
 }
 
 static int wait_for_interrupt(void *ctx, int msecs) {