[PATCH 5.8 623/633] ath10k: check idx validity in __ath10k_htt_rx_ring_fill_n()

Greg Kroah-Hartman
2020-10-27T15:20:40Z

From: Zekun Shen <bruceshenzk@gmail.com>

[ Upstream commit bad60b8d1a7194df38fd7fe4b22f3f4dcf775099 ]

The idx in __ath10k_htt_rx_ring_fill_n function lives in
consistent dma region writable by the device. Malfunctional
or malicious device could manipulate such idx to have a OOB
write. Either by
htt->rx_ring.netbufs_ring[idx] = skb;
or by
ath10k_htt_set_paddrs_ring(htt, paddr, idx);

The idx can also be negative as it's signed, giving a large
memory space to write to.

It's possibly exploitable by corruptting a legit pointer with
a skb pointer. And then fill skb with payload as rougue object.

Part of the log here. Sometimes it appears as UAF when writing
to a freed memory by chance.

[ 15.594376] BUG: unable to handle page fault for address: ffff887f5c1804f0
[ 15.595483] #PF: supervisor write access in kernel mode
[ 15.596250] #PF: error_code(0x0002) - not-present page
[ 15.597013] PGD 0 P4D 0
[ 15.597395] Oops: 0002 [#1] SMP KASAN PTI
[ 15.597967] CPU: 0 PID: 82 Comm: kworker/u2:2 Not tainted 5.6.0 #69
[ 15.598843] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996),
BIOS rel-1.12.1-0-ga5cab58e9a3f-prebuilt.qemu.org 04/01/2014
[ 15.600438] Workqueue: ath10k_wq ath10k_core_register_work [ath10k_core]
[ 15.601389] RIP: 0010:__ath10k_htt_rx_ring_fill_n
(linux/drivers/net/wireless/ath/ath10k/htt_rx.c:173) ath10k_core

Signed-off-by: Zekun Shen <bruceshenzk@gmail.com>
Signed-off-by: Kalle Valo <kvalo@codeaurora.org>
Link: https://lore.kernel.org/r/20200623221105.3486-1-bruceshenzk@gmail.com
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
drivers/net/wireless/ath/ath10k/htt_rx.c | 8 ++++++++
1 file changed, 8 insertions(+)

diff --git a/drivers/net/wireless/ath/ath10k/htt_rx.c b/drivers/net/wireless/ath/ath10k/htt_rx.c
index d787cbead56ab..215ade6faf328 100644
--- a/drivers/net/wireless/ath/ath10k/htt_rx.c
+++ b/drivers/net/wireless/ath/ath10k/htt_rx.c
@@ -142,6 +142,14 @@ static int __ath10k_htt_rx_ring_fill_n(struct ath10k_htt *htt, int num)
BUILD_BUG_ON(HTT_RX_RING_FILL_LEVEL >= HTT_RX_RING_SIZE / 2);

idx = __le32_to_cpu(*htt->rx_ring.alloc_idx.vaddr);
+
+ if (idx < 0 || idx >= htt->rx_ring.size) {
+ ath10k_err(htt->ar, "rx ring index is not valid, firmware malfunctioning?\n");
+ idx &= htt->rx_ring.size_mask;
+ ret = -ENOMEM;
+ goto fail;
+ }
+
while (num > 0) {
skb = dev_alloc_skb(HTT_RX_BUF_SIZE + HTT_RX_DESC_ALIGN);
if (!skb) {
--
2.25.1