diff mbox series

bus: mhi: host: Detect events pointing to unexpected TREs

Message ID 20250521163110.571893-1-quic_yabdulra@quicinc.com
State New
Headers show
Series bus: mhi: host: Detect events pointing to unexpected TREs | expand

Commit Message

Youssef Samir May 21, 2025, 4:31 p.m. UTC 
When a remote device sends a completion event to the host, it contains a
pointer to the consumed TRE. The host uses this pointer to process all of
the TREs between it and the host's local copy of the ring's read pointer.
This works when processing completion for chained transactions, but can
lead to nasty results if the device sends an event for a single-element
transaction with a read pointer that is multiple elements ahead of the
host's read pointer.

For instance, if the host accesses an event ring while the device is
updating it, the pointer inside of the event might still point to an old
TRE. If the host uses the channel's xfer_cb() to directly free the buffer
pointed to by the TRE, the buffer will be double-freed.

Validate the pointer inside an event before processing it.

Fixes: 1d3173a3bae7 ("bus: mhi: core: Add support for processing events from client device")
Signed-off-by: Youssef Samir <quic_yabdulra@quicinc.com>

---
 drivers/bus/mhi/host/main.c | 12 +++++++++++-
 1 file changed, 11 insertions(+), 1 deletion(-)
diff mbox series

Patch

diff --git a/drivers/bus/mhi/host/main.c b/drivers/bus/mhi/host/main.c
index aa8a0ef697c7..57dc9c5c0d84 100644
--- a/drivers/bus/mhi/host/main.c
+++ b/drivers/bus/mhi/host/main.c
@@ -602,7 +602,7 @@  static int parse_xfer_event(struct mhi_controller *mhi_cntrl,
 	{
 		dma_addr_t ptr = MHI_TRE_GET_EV_PTR(event);
 		struct mhi_ring_element *local_rp, *ev_tre;
-		void *dev_rp;
+		void *dev_rp, *next_rp;
 		struct mhi_buf_info *buf_info;
 		u16 xfer_len;
 
@@ -621,6 +621,16 @@  static int parse_xfer_event(struct mhi_controller *mhi_cntrl,
 		result.dir = mhi_chan->dir;
 
 		local_rp = tre_ring->rp;
+
+		next_rp = local_rp + 1;
+		if (next_rp >= tre_ring->base + tre_ring->len)
+			next_rp = tre_ring->base;
+		if (dev_rp != next_rp && !MHI_TRE_DATA_GET_CHAIN(local_rp)) {
+			dev_err(&mhi_cntrl->mhi_dev->dev,
+				"Event element points to an unexpected tre\n");
+			break;
+		}
+
 		while (local_rp != dev_rp) {
 			buf_info = buf_ring->rp;
 			/* If it's the last TRE, get length from the event */