diag: Protect md_info structure while reallocation

The possibility of md_info structure being accessed simultaneously
by two threads is prevented by synchronizing while buffer
reallocation for hdlc encoding. Extend the scope of protection to
md_info till queueing the write to sdcard.

CRs-Fixed: 2279473
Change-Id: I75ddb102adfc6c79f35ed69914c9140cb82894c9
Signed-off-by: Manoj Prabhu B <bmanoj@codeaurora.org>

drivers/char/diag/diag_memorydevice.c

@@ -164,11 +164,12 @@ int diag_md_write(int id, unsigned char *buf, int len, int ctx)
 		return -EIO;
 	}
 	pid = session_info->pid;
-	mutex_unlock(&driver->md_session_lock);
 
 	ch = &diag_md[id];
-	if (!ch || !ch->md_info_inited)
+	if (!ch || !ch->md_info_inited) {
+		mutex_unlock(&driver->md_session_lock);
 		return -EINVAL;
+	}
 
 	spin_lock_irqsave(&ch->lock, flags);
 	for (i = 0; i < ch->num_tbl_entries && !found; i++) {
@@ -184,8 +185,10 @@ int diag_md_write(int id, unsigned char *buf, int len, int ctx)
 	}
 	spin_unlock_irqrestore(&ch->lock, flags);
 
-	if (found)
+	if (found) {
+		mutex_unlock(&driver->md_session_lock);
 		return -ENOMEM;
+	}
 
 	spin_lock_irqsave(&ch->lock, flags);
 	for (i = 0; i < ch->num_tbl_entries && !found; i++) {
@@ -198,6 +201,7 @@ int diag_md_write(int id, unsigned char *buf, int len, int ctx)
 		}
 	}
 	spin_unlock_irqrestore(&ch->lock, flags);
+	mutex_unlock(&driver->md_session_lock);
 
 	if (!found) {
 		pr_err_ratelimited("diag: Unable to find an empty space in table, please reduce logging rate, proc: %d\n",

drivers/char/diag/diagfwd_peripheral.c

@@ -191,6 +191,7 @@ static int check_bufsize_for_encoding(struct diagfwd_buf_t *buf, uint32_t len)
 {
 	int i, ctx = 0;
 	uint32_t max_size = 0;
+	unsigned long flags;
 	unsigned char *temp_buf = NULL;
 	struct diag_md_info *ch = NULL;
 
@@ -205,11 +206,16 @@ static int check_bufsize_for_encoding(struct diagfwd_buf_t *buf, uint32_t len)
 			max_size = MAX_PERIPHERAL_HDLC_BUF_SZ;
 		}
 
+		mutex_lock(&driver->md_session_lock);
 		if (buf->len < max_size) {
 			if (driver->logging_mode == DIAG_MEMORY_DEVICE_MODE) {
 				ch = &diag_md[DIAG_LOCAL_PROC];
-				for (i = 0; ch != NULL &&
-						i < ch->num_tbl_entries; i++) {
+				if (!ch || !ch->md_info_inited) {
+					mutex_unlock(&driver->md_session_lock);
+					return -EINVAL;
+				}
+				spin_lock_irqsave(&ch->lock, flags);
+				for (i = 0; i < ch->num_tbl_entries; i++) {
 					if (ch->tbl[i].buf == buf->data) {
 						ctx = ch->tbl[i].ctx;
 						ch->tbl[i].buf = NULL;
@@ -222,18 +228,22 @@ static int check_bufsize_for_encoding(struct diagfwd_buf_t *buf, uint32_t len)
 						break;
 					}
 				}
+				spin_unlock_irqrestore(&ch->lock, flags);
 			}
 			temp_buf = krealloc(buf->data, max_size +
 						APF_DIAG_PADDING,
 					    GFP_KERNEL);
-			if (!temp_buf)
+			if (!temp_buf) {
+				mutex_unlock(&driver->md_session_lock);
 				return -ENOMEM;
+			}
 			DIAG_LOG(DIAG_DEBUG_PERIPHERALS,
 			"Reallocated data buffer: %pK with size: %d\n",
 			temp_buf, max_size);
 			buf->data = temp_buf;
 			buf->len = max_size;
 		}
+		mutex_unlock(&driver->md_session_lock);
 	}
 
 	return buf->len;