netdev - [PATCH AUTOSEL 5.10 15/43] stmmac_pci: Fix underflow size in stmmac

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Message-Id: <20211130145022.945517-15-sashal@kernel.org>
Date:   Tue, 30 Nov 2021 09:49:52 -0500
From:   Sasha Levin <sashal@...nel.org>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
Cc:     Zekun Shen <bruceshenzk@...il.com>,
        Brendan Dolan-Gavitt <brendandg@....edu>,
        "David S . Miller" <davem@...emloft.net>,
        Sasha Levin <sashal@...nel.org>, peppe.cavallaro@...com,
        alexandre.torgue@...s.st.com, joabreu@...opsys.com,
        kuba@...nel.org, mcoquelin.stm32@...il.com, netdev@...r.kernel.org,
        linux-stm32@...md-mailman.stormreply.com,
        linux-arm-kernel@...ts.infradead.org
Subject: [PATCH AUTOSEL 5.10 15/43] stmmac_pci: Fix underflow size in stmmac_rx

From: Zekun Shen <bruceshenzk@...il.com>

[ Upstream commit 0f296e782f21dc1c55475a3c107ac68ab09cc1cf ]

This bug report came up when we were testing the device driver
by fuzzing. It shows that buf1_len can get underflowed and be
0xfffffffc (4294967292).

This bug is triggerable with a compromised/malfunctioning device.
We found the bug through QEMU emulation tested the patch with
emulation. We did NOT test it on real hardware.

Attached is the bug report by fuzzing.

BUG: KASAN: use-after-free in stmmac_napi_poll_rx+0x1c08/0x36e0 [stmmac]
Read of size 4294967292 at addr ffff888016358000 by task ksoftirqd/0/9

CPU: 0 PID: 9 Comm: ksoftirqd/0 Tainted: G        W         5.6.0 #1
Call Trace:
 dump_stack+0x76/0xa0
 print_address_description.constprop.0+0x16/0x200
 ? stmmac_napi_poll_rx+0x1c08/0x36e0 [stmmac]
 ? stmmac_napi_poll_rx+0x1c08/0x36e0 [stmmac]
 __kasan_report.cold+0x37/0x7c
 ? stmmac_napi_poll_rx+0x1c08/0x36e0 [stmmac]
 kasan_report+0xe/0x20
 check_memory_region+0x15a/0x1d0
 memcpy+0x20/0x50
 stmmac_napi_poll_rx+0x1c08/0x36e0 [stmmac]
 ? stmmac_suspend+0x850/0x850 [stmmac]
 ? __next_timer_interrupt+0xba/0xf0
 net_rx_action+0x363/0xbd0
 ? call_timer_fn+0x240/0x240
 ? __switch_to_asm+0x40/0x70
 ? napi_busy_loop+0x520/0x520
 ? __schedule+0x839/0x15a0
 __do_softirq+0x18c/0x634
 ? takeover_tasklets+0x5f0/0x5f0
 run_ksoftirqd+0x15/0x20
 smpboot_thread_fn+0x2f1/0x6b0
 ? smpboot_unregister_percpu_thread+0x160/0x160
 ? __kthread_parkme+0x80/0x100
 ? smpboot_unregister_percpu_thread+0x160/0x160
 kthread+0x2b5/0x3b0
 ? kthread_create_on_node+0xd0/0xd0
 ret_from_fork+0x22/0x40

Reported-by: Brendan Dolan-Gavitt <brendandg@....edu>
Signed-off-by: Zekun Shen <bruceshenzk@...il.com>
Signed-off-by: David S. Miller <davem@...emloft.net>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 drivers/net/ethernet/stmicro/stmmac/stmmac_main.c | 9 +++++----
 1 file changed, 5 insertions(+), 4 deletions(-)

diff --git a/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c b/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
index 4a75e73f06bbd..197029b4c11a1 100644
--- a/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
+++ b/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
@@ -3873,12 +3873,13 @@ static int stmmac_rx(struct stmmac_priv *priv, int limit, u32 queue)
 		if (likely(!(status & rx_not_ls)) &&
 		    (likely(priv->synopsys_id >= DWMAC_CORE_4_00) ||
 		     unlikely(status != llc_snap))) {
-			if (buf2_len)
+			if (buf2_len) {
 				buf2_len -= ETH_FCS_LEN;
-			else
+				len -= ETH_FCS_LEN;
+			} else if (buf1_len) {
 				buf1_len -= ETH_FCS_LEN;
-
-			len -= ETH_FCS_LEN;
+				len -= ETH_FCS_LEN;
+			}
 		}
 
 		if (!skb) {
-- 
2.33.0