[PATCH v1 4/5] misc: fastrpc: Remove buffer from list prior to unmap operation

[Ekansh Gupta]

fastrpc_req_munmap_impl() is called to unmap any buffer. The buffer is
getting removed from the list after it is unmapped from DSP. This can
create potential race conditions if any other thread removes the entry
from list while unmap operation is ongoing. Remove the entry before
calling unmap operation.

Fixes: 2419e55e532de ("misc: fastrpc: add mmap/unmap support")
Cc: stable at kernel.org
Signed-off-by: Ekansh Gupta <ekansh.gupta at oss.qualcomm.com>
---
 drivers/misc/fastrpc.c | 29 ++++++++++++++++++++++-------
 1 file changed, 22 insertions(+), 7 deletions(-)

diff --git a/drivers/misc/fastrpc.c b/drivers/misc/fastrpc.c
index b629e24f00bc..d54368bf8c5c 100644
--- a/drivers/misc/fastrpc.c
+++ b/drivers/misc/fastrpc.c
@@ -1868,9 +1868,6 @@ static int fastrpc_req_munmap_impl(struct fastrpc_user *fl, struct fastrpc_buf *
 				      &args[0]);
 	if (!err) {
 		dev_dbg(dev, "unmmap\tpt 0x%09lx OK\n", buf->raddr);
-		spin_lock(&fl->lock);
-		list_del(&buf->node);
-		spin_unlock(&fl->lock);
 		fastrpc_buf_free(buf);
 	} else {
 		dev_err(dev, "unmmap\tpt 0x%09lx ERROR\n", buf->raddr);
@@ -1884,13 +1881,15 @@ static int fastrpc_req_munmap(struct fastrpc_user *fl, char __user *argp)
 	struct fastrpc_buf *buf = NULL, *iter, *b;
 	struct fastrpc_req_munmap req;
 	struct device *dev = fl->sctx->dev;
+	int err;
 
 	if (copy_from_user(&req, argp, sizeof(req)))
 		return -EFAULT;
 
 	spin_lock(&fl->lock);
 	list_for_each_entry_safe(iter, b, &fl->mmaps, node) {
-		if ((iter->raddr == req.vaddrout) && (iter->size == req.size)) {
+		if (iter->raddr == req.vaddrout && iter->size == req.size) {
+			list_del(&iter->node);
 			buf = iter;
 			break;
 		}
@@ -1903,7 +1902,14 @@ static int fastrpc_req_munmap(struct fastrpc_user *fl, char __user *argp)
 		return -EINVAL;
 	}
 
-	return fastrpc_req_munmap_impl(fl, buf);
+	err = fastrpc_req_munmap_impl(fl, buf);
+	if (err) {
+		spin_lock(&fl->lock);
+		list_add_tail(&buf->node, &fl->mmaps);
+		spin_unlock(&fl->lock);
+	}
+
+	return err;
 }
 
 static int fastrpc_req_mmap(struct fastrpc_user *fl, char __user *argp)
@@ -1997,14 +2003,23 @@ static int fastrpc_req_mmap(struct fastrpc_user *fl, char __user *argp)
 
 	if (copy_to_user((void __user *)argp, &req, sizeof(req))) {
 		err = -EFAULT;
-		goto err_assign;
+		goto err_copy;
 	}
 
 	dev_dbg(dev, "mmap\t\tpt 0x%09lx OK [len 0x%08llx]\n",
 		buf->raddr, buf->size);
 
 	return 0;
-
+err_copy:
+	if (req.flags == ADSP_MMAP_REMOTE_HEAP_ADDR) {
+		spin_lock_irqsave(&fl->cctx->lock, flags);
+		list_del(&buf->node);
+		spin_unlock_irqrestore(&fl->cctx->lock, flags);
+	} else {
+		spin_lock(&fl->lock);
+		list_del(&buf->node);
+		spin_unlock(&fl->lock);
+	}
 err_assign:
 	fastrpc_req_munmap_impl(fl, buf);
 
-- 
2.34.1