Commit 9446fa16 authored by Abel Vesa's avatar Abel Vesa Committed by Greg Kroah-Hartman
Browse files

misc: fastrpc: Fix use-after-free and race in fastrpc_map_find 



Currently, there is a race window between the point when the mutex is
unlocked in fastrpc_map_lookup and the reference count increasing
(fastrpc_map_get) in fastrpc_map_find, which can also lead to
use-after-free.

So lets merge fastrpc_map_find into fastrpc_map_lookup which allows us
to both protect the maps list by also taking the &fl->lock spinlock and
the reference count, since the spinlock will be released only after.
Add take_ref argument to make this suitable for all callers.

Fixes: 8f6c1d8c ("misc: fastrpc: Add fdlist implementation")
Cc: stable <stable@kernel.org>
Co-developed-by: default avatarOla Jeppsson <ola@snap.com>
Signed-off-by: default avatarOla Jeppsson <ola@snap.com>
Signed-off-by: default avatarAbel Vesa <abel.vesa@linaro.org>
Signed-off-by: default avatarSrinivas Kandagatla <srinivas.kandagatla@linaro.org>
Link: https://lore.kernel.org/r/20221124174941.418450-2-srinivas.kandagatla@linaro.org


Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
parent 5023adc3

drivers/misc/fastrpc.c

+21 −20
Original line number Diff line number Diff line
@@ -351,30 +351,31 @@ static void fastrpc_map_get(struct fastrpc_map *map) 




static int fastrpc_map_lookup(struct fastrpc_user *fl, int fd,

			    struct fastrpc_map **ppmap)

			    struct fastrpc_map **ppmap, bool take_ref)

{

	struct fastrpc_session_ctx *sess = fl->sctx;

	struct fastrpc_map *map = NULL;

	int ret = -ENOENT;



	mutex_lock(&fl->mutex);

	spin_lock(&fl->lock);

	list_for_each_entry(map, &fl->maps, node) {

		if (map->fd == fd) {

			*ppmap = map;

			mutex_unlock(&fl->mutex);

			return 0;

		if (map->fd != fd)

			continue;



		if (take_ref) {

			ret = fastrpc_map_get(map);

			if (ret) {

				dev_dbg(sess->dev, "%s: Failed to get map fd=%d ret=%d\n",

					__func__, fd, ret);

				break;

			}

		}

	mutex_unlock(&fl->mutex);



	return -ENOENT;

		*ppmap = map;

		ret = 0;

		break;

	}



static int fastrpc_map_find(struct fastrpc_user *fl, int fd,

			    struct fastrpc_map **ppmap)

{

	int ret = fastrpc_map_lookup(fl, fd, ppmap);



	if (!ret)

		fastrpc_map_get(*ppmap);

	spin_unlock(&fl->lock);



	return ret;

}
@@ -746,7 +747,7 @@ static int fastrpc_map_create(struct fastrpc_user *fl, int fd, 
	struct fastrpc_map *map = NULL;

	int err = 0;



	if (!fastrpc_map_find(fl, fd, ppmap))

	if (!fastrpc_map_lookup(fl, fd, ppmap, true))

		return 0;



	map = kzalloc(sizeof(*map), GFP_KERNEL);
@@ -1070,7 +1071,7 @@ static int fastrpc_put_args(struct fastrpc_invoke_ctx *ctx, 
	for (i = 0; i < FASTRPC_MAX_FDLIST; i++) {

		if (!fdlist[i])

			break;

		if (!fastrpc_map_lookup(fl, (int)fdlist[i], &mmap))

		if (!fastrpc_map_lookup(fl, (int)fdlist[i], &mmap, false))

			fastrpc_map_put(mmap);

	}