linux-kernel - [PATCH v2 1/4] misc: fastrpc: Add NULL check to fastrpc_buf

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Message-Id: <20260115082851.570-2-jianping.li@oss.qualcomm.com>
Date: Thu, 15 Jan 2026 16:28:48 +0800
From: Jianping Li <jianping.li@....qualcomm.com>
To: srini@...nel.org, amahesh@....qualcomm.com, arnd@...db.de,
        gregkh@...uxfoundation.org, linux-arm-msm@...r.kernel.org
Cc: Ekansh Gupta <ekansh.gupta@....qualcomm.com>, thierry.escande@...aro.org,
        abelvesa@...nel.org, dri-devel@...ts.freedesktop.org,
        linux-kernel@...r.kernel.org, quic_chennak@...cinc.com,
        stable@...nel.org, Jianping Li <jianping.li@....qualcomm.com>
Subject: [PATCH v2 1/4] misc: fastrpc: Add NULL check to fastrpc_buf_free to prevent crash

From: Ekansh Gupta <ekansh.gupta@....qualcomm.com>

The fastrpc_buf_free function currently does not handle the case where
the input buffer pointer (buf) is NULL. This can lead to a null pointer
dereference, causing a crash or undefined behavior when the function
attempts to access members of the buf structure. Add a NULL check to
ensure safe handling of NULL pointers and prevent potential crashes.

Fixes: c68cfb718c8f9 ("misc: fastrpc: Add support for context Invoke method")
Cc: stable@...nel.org
Co-developed-by: Ekansh Gupta <ekansh.gupta@....qualcomm.com>
Signed-off-by: Ekansh Gupta <ekansh.gupta@....qualcomm.com>
Signed-off-by: Jianping Li <jianping.li@....qualcomm.com>
---
 drivers/misc/fastrpc.c | 12 ++++++------
 1 file changed, 6 insertions(+), 6 deletions(-)

diff --git a/drivers/misc/fastrpc.c b/drivers/misc/fastrpc.c
index 4f5a79c50f58..515a43c9d95d 100644
--- a/drivers/misc/fastrpc.c
+++ b/drivers/misc/fastrpc.c
@@ -414,6 +414,9 @@ static int fastrpc_map_lookup(struct fastrpc_user *fl, int fd,
 
 static void fastrpc_buf_free(struct fastrpc_buf *buf)
 {
+	if (!buf)
+		return;
+
 	dma_free_coherent(buf->dev, buf->size, buf->virt,
 			  fastrpc_ipa_to_dma_addr(buf->fl->cctx, buf->dma_addr));
 	kfree(buf);
@@ -510,8 +513,7 @@ static void fastrpc_context_free(struct kref *ref)
 	for (i = 0; i < ctx->nbufs; i++)
 		fastrpc_map_put(ctx->maps[i]);
 
-	if (ctx->buf)
-		fastrpc_buf_free(ctx->buf);
+	fastrpc_buf_free(ctx->buf);
 
 	spin_lock_irqsave(&cctx->lock, flags);
 	idr_remove(&cctx->ctx_idr, ctx->ctxid >> 4);
@@ -1591,8 +1593,7 @@ static int fastrpc_device_release(struct inode *inode, struct file *file)
 	list_del(&fl->user);
 	spin_unlock_irqrestore(&cctx->lock, flags);
 
-	if (fl->init_mem)
-		fastrpc_buf_free(fl->init_mem);
+	fastrpc_buf_free(fl->init_mem);
 
 	list_for_each_entry_safe(ctx, n, &fl->pending, node) {
 		list_del(&ctx->node);
@@ -2492,8 +2493,7 @@ static void fastrpc_rpmsg_remove(struct rpmsg_device *rpdev)
 	list_for_each_entry_safe(buf, b, &cctx->invoke_interrupted_mmaps, node)
 		list_del(&buf->node);
 
-	if (cctx->remote_heap)
-		fastrpc_buf_free(cctx->remote_heap);
+	fastrpc_buf_free(cctx->remote_heap);
 
 	of_platform_depopulate(&rpdev->dev);
 
-- 
2.43.0