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SubjectRe: [PATCH 2/3] misc: fastrpc: Don't remove map on creater_process and device_release
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On 02/09/2022 16:14, Abel Vesa wrote:
> Do not remove the map from the list on error path in
> fastrpc_init_create_process, instead call fastrpc_map_put, to avoid
> use-after-free. Do not remove it on fastrpc_device_release either,
> call fastrpc_map_put instead.
>
> The fastrpc_free_map is the only proper place to remove the map.
> This is called only after the reference count is 0.
>
> Fixes: b49f6d83e290f ("misc: fastrpc: Fix a possible double free")
> Co-developed-by: Ola Jeppsson <ola@snap.com>
> Signed-off-by: Ola Jeppsson <ola@snap.com>
> Signed-off-by: Abel Vesa <abel.vesa@linaro.org>
> ---

Reviewed-by: Srinivas Kandagatla <srinivas.kandagatla@linaro.org>

> drivers/misc/fastrpc.c | 18 +++++++++---------
> 1 file changed, 9 insertions(+), 9 deletions(-)
>
> diff --git a/drivers/misc/fastrpc.c b/drivers/misc/fastrpc.c
> index 0c816a11eeec..50c17f5da3a8 100644
> --- a/drivers/misc/fastrpc.c
> +++ b/drivers/misc/fastrpc.c
> @@ -316,6 +316,13 @@ static void fastrpc_free_map(struct kref *ref)
> dma_buf_put(map->buf);
> }
>
> + if (map->fl) {
> + spin_lock(&map->fl->lock);
> + list_del(&map->node);
> + spin_unlock(&map->fl->lock);
> + map->fl = NULL;
> + }
> +
> kfree(map);
> }
>
> @@ -1266,12 +1273,7 @@ static int fastrpc_init_create_process(struct fastrpc_user *fl,
> fl->init_mem = NULL;
> fastrpc_buf_free(imem);
> err_alloc:
> - if (map) {
> - spin_lock(&fl->lock);
> - list_del(&map->node);
> - spin_unlock(&fl->lock);
> - fastrpc_map_put(map);
> - }
> + fastrpc_map_put(map);
> err:
> kfree(args);
>
> @@ -1347,10 +1349,8 @@ static int fastrpc_device_release(struct inode *inode, struct file *file)
> fastrpc_context_put(ctx);
> }
>
> - list_for_each_entry_safe(map, m, &fl->maps, node) {
> - list_del(&map->node);
> + list_for_each_entry_safe(map, m, &fl->maps, node)
> fastrpc_map_put(map);
> - }
>
> list_for_each_entry_safe(buf, b, &fl->mmaps, node) {
> list_del(&buf->node);

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