linux-kernel - [PATCH v4] misc: fastrpc: possible double-free of cctx->remote

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Message-Id: <20260128042600.2641857-1-xjdeng@buaa.edu.cn>
Date: Wed, 28 Jan 2026 12:26:00 +0800
From: Xingjing Deng <micro6947@...il.com>
To: srini@...nel.org,
	amahesh@....qualcomm.com,
	arnd@...db.de,
	gregkh@...uxfoundation.org
Cc: dri-devel@...ts.freedesktop.org,
	linux-arm-msm@...r.kernel.org,
	linux-kernel@...r.kernel.org,
	Xingjing Deng <xjdeng@...a.edu.cn>,
	stable@...r.kernel.org
Subject: [PATCH v4] misc: fastrpc: possible double-free of cctx->remote_heap

fastrpc_init_create_static_process() may free cctx->remote_heap on the
err_map path but does not clear the pointer. Later, fastrpc_rpmsg_remove()
frees cctx->remote_heap again if it is non-NULL, which can lead to a
double-free if the INIT_CREATE_STATIC ioctl hits the error path and the rpmsg
device is subsequently removed/unbound.

Clear cctx->remote_heap after freeing it in the error path to prevent the
later cleanup from freeing it again.

This issue was detected by a private static analysis tool.
No actual hardware testing was performed as the issue is purely
code-level and verified via static analysis.

Fixes: 0871561055e66 ("misc: fastrpc: Add support for audiopd")
Cc: stable@...r.kernel.org # 6.2+
Signed-off-by: Xingjing Deng <xjdeng@...a.edu.cn>
---
v4:
- Add description of the detection tool.
- Link to v3: https://lore.kernel.org/linux-arm-msm/20260117140959.879035-1-xjdeng@buaa.edu.cn/T/#u

v3:
- Adjust the email format.
- Link to v2: https://lore.kernel.org/linux-arm-msm/2026011650-gravitate-happily-5d0c@gregkh/T/#t

v2:
- Add Fixes: and Cc: stable@...r.kernel.org.
- Link to v1: https://lore.kernel.org/linux-arm-msm/2026011227-casualty-rephrase-9381@gregkh/T/#t

 drivers/misc/fastrpc.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/drivers/misc/fastrpc.c b/drivers/misc/fastrpc.c
index ee652ef01534..fb3b54e05928 100644
--- a/drivers/misc/fastrpc.c
+++ b/drivers/misc/fastrpc.c
@@ -1370,6 +1370,7 @@ static int fastrpc_init_create_static_process(struct fastrpc_user *fl,
 	}
 err_map:
 	fastrpc_buf_free(fl->cctx->remote_heap);
+	fl->cctx->remote_heap = NULL;
 err_name:
 	kfree(name);
 err:
-- 
2.25.1