[PATCH v5] misc: fastrpc: possible double-free of cctx->remote_heap

[Xingjing Deng]

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 found by an in-house analysis workflow that extracts AST-based
information and runs static checks, with LLM assistance for triage, and was
confirmed by manual code review.
No hardware testing was performed.

Fixes: 0871561055e66 ("misc: fastrpc: Add support for audiopd")
Cc: stable@xxxxxxxxxxxxxxx # 6.2+
Signed-off-by: Xingjing Deng <xjdeng@xxxxxxxxxxx>
---
v5: 
- Add the detail description of how the tool detect.
- Link to v4: https://lore.kernel.org/linux-arm-msm/20260128042600.2641857-1-xjdeng@xxxxxxxxxxx/

v4:
- Add description of the detection tool.
- Link to v3: https://lore.kernel.org/linux-arm-msm/20260117140959.879035-1-xjdeng@xxxxxxxxxxx/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@xxxxxxxxxxxxxxx.
- 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