From: Ola Jeppsson ola@snap.com
commit 96b328d119eca7563c1edcc4e1039a62e6370ecb upstream.
It is possible that in between calling fastrpc_map_get() until map->fl->lock is taken in fastrpc_free_map(), another thread can call fastrpc_map_lookup() and get a reference to a map that is about to be deleted.
Rewrite fastrpc_map_get() to only increase the reference count of a map if it's non-zero. Propagate this to callers so they can know if a map is about to be deleted.
Fixes this warning: refcount_t: addition on 0; use-after-free. WARNING: CPU: 5 PID: 10100 at lib/refcount.c:25 refcount_warn_saturate ... Call trace: refcount_warn_saturate [fastrpc_map_get inlined] [fastrpc_map_lookup inlined] fastrpc_map_create fastrpc_internal_invoke fastrpc_device_ioctl __arm64_sys_ioctl invoke_syscall
Fixes: c68cfb718c8f ("misc: fastrpc: Add support for context Invoke method") Cc: stable stable@kernel.org Signed-off-by: Ola Jeppsson ola@snap.com Signed-off-by: Abel Vesa abel.vesa@linaro.org Signed-off-by: Srinivas Kandagatla srinivas.kandagatla@linaro.org Link: https://lore.kernel.org/r/20221124174941.418450-4-srinivas.kandagatla@linaro... Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- drivers/misc/fastrpc.c | 8 +++++--- 1 file changed, 5 insertions(+), 3 deletions(-)
--- a/drivers/misc/fastrpc.c +++ b/drivers/misc/fastrpc.c @@ -234,10 +234,12 @@ static void fastrpc_map_put(struct fastr kref_put(&map->refcount, fastrpc_free_map); }
-static void fastrpc_map_get(struct fastrpc_map *map) +static int fastrpc_map_get(struct fastrpc_map *map) { - if (map) - kref_get(&map->refcount); + if (!map) + return -ENOENT; + + return kref_get_unless_zero(&map->refcount) ? 0 : -ENOENT; }
static int fastrpc_map_find(struct fastrpc_user *fl, int fd,