From 647d446d66e493d23ca1047fa8492b0269674530 Mon Sep 17 00:00:00 2001
From: Sean Young <sean@mess.org>
Date: Wed, 23 Jun 2021 22:37:54 +0100
Subject: [PATCH] media, bpf: Do not copy more entries than user space requested
Git-commit: 647d446d66e493d23ca1047fa8492b0269674530
Patch-mainline: v5.14-rc1
References: git-fixes

The syscall bpf(BPF_PROG_QUERY, &attr) should use the prog_cnt field to
see how many entries user space provided and return ENOSPC if there are
more programs than that. Before this patch, this is not checked and
ENOSPC is never returned.

Note that one lirc device is limited to 64 bpf programs, and user space
I'm aware of -- ir-keytable -- always gives enough space for 64 entries
already. However, we should not copy program ids than are requested.

Signed-off-by: Sean Young <sean@mess.org>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Link: https://lore.kernel.org/bpf/20210623213754.632-1-sean@mess.org
Acked-by: Takashi Iwai <tiwai@suse.de>

---
 drivers/media/rc/bpf-lirc.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/drivers/media/rc/bpf-lirc.c b/drivers/media/rc/bpf-lirc.c
index 3fe3edd80876..afae0afe3f81 100644
--- a/drivers/media/rc/bpf-lirc.c
+++ b/drivers/media/rc/bpf-lirc.c
@@ -326,7 +326,8 @@ int lirc_prog_query(const union bpf_attr *attr, union bpf_attr __user *uattr)
 	}
 
 	if (attr->query.prog_cnt != 0 && prog_ids && cnt)
-		ret = bpf_prog_array_copy_to_user(progs, prog_ids, cnt);
+		ret = bpf_prog_array_copy_to_user(progs, prog_ids,
+						  attr->query.prog_cnt);
 
 unlock:
 	mutex_unlock(&ir_raw_handler_lock);
-- 
2.26.2