tee: shm: fix shm leak in register_shm_helper()

register_shm_helper() allocates shm before calling
iov_iter_npages(). If iov_iter_npages() returns 0, the function
jumps to err_ctx_put and leaks shm.

This can be triggered by TEE_IOC_SHM_REGISTER with
struct tee_ioctl_shm_register_data where length is 0.

Jump to err_free_shm instead.

Fixes: 7bdee41575 ("tee: Use iov_iter to better support shared buffer registration")
Cc: [email protected]
Cc: [email protected]
Signed-off-by: Georgiy Osokin <[email protected]>
Reviewed-by: Sumit Garg <[email protected]>
Signed-off-by: Jens Wiklander <[email protected]>

drivers/tee/tee_shm.c

@@ -435,7 +435,7 @@ register_shm_helper(struct tee_context *ctx, struct iov_iter *iter, u32 flags,
 	num_pages = iov_iter_npages(iter, INT_MAX);
 	if (!num_pages) {
 		ret = ERR_PTR(-ENOMEM);
-		goto err_ctx_put;
+		goto err_free_shm;
 	}
 
 	shm->pages = kzalloc_objs(*shm->pages, num_pages);