[PATCH AUTOSEL 5.15 22/68] stmmac_pci: Fix underflow size in stmmac_rx

Sasha Levin
2021-11-30T14:49:09Z

From: Zekun Shen <bruceshenzk@gmail.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@nyu.edu>
Signed-off-by: Zekun Shen <bruceshenzk@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Sasha Levin <sashal@kernel.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 0ab20e2f984b9..348ad489f154c 100644
--- a/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
+++ b/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
@@ -5153,12 +5153,13 @@ 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