From: Michael Braun michael-dev@fami-braun.de
stable inclusion from linux-4.19.184 commit 9943741c2792a7f1d091aad38f496ed6eb7681c4 CVE: CVE-2021-29264
--------------------------------
[ Upstream commit d8861bab48b6c1fc3cdbcab8ff9d1eaea43afe7f ]
When using jumbo packets and overrunning rx queue with napi enabled, the following sequence is observed in gfar_add_rx_frag:
| lstatus | | skb | t | lstatus, size, flags | first | len, data_len, *ptr | ---+--------------------------------------+-------+-----------------------+ 13 | 18002348, 9032, INTERRUPT LAST | 0 | 9600, 8000, f554c12e | 12 | 10000640, 1600, INTERRUPT | 0 | 8000, 6400, f554c12e | 11 | 10000640, 1600, INTERRUPT | 0 | 6400, 4800, f554c12e | 10 | 10000640, 1600, INTERRUPT | 0 | 4800, 3200, f554c12e | 09 | 10000640, 1600, INTERRUPT | 0 | 3200, 1600, f554c12e | 08 | 14000640, 1600, INTERRUPT FIRST | 0 | 1600, 0, f554c12e | 07 | 14000640, 1600, INTERRUPT FIRST | 1 | 0, 0, f554c12e | 06 | 1c000080, 128, INTERRUPT LAST FIRST | 1 | 0, 0, abf3bd6e | 05 | 18002348, 9032, INTERRUPT LAST | 0 | 8000, 6400, c5a57780 | 04 | 10000640, 1600, INTERRUPT | 0 | 6400, 4800, c5a57780 | 03 | 10000640, 1600, INTERRUPT | 0 | 4800, 3200, c5a57780 | 02 | 10000640, 1600, INTERRUPT | 0 | 3200, 1600, c5a57780 | 01 | 10000640, 1600, INTERRUPT | 0 | 1600, 0, c5a57780 | 00 | 14000640, 1600, INTERRUPT FIRST | 1 | 0, 0, c5a57780 |
So at t=7 a new packets is started but not finished, probably due to rx overrun - but rx overrun is not indicated in the flags. Instead a new packets starts at t=8. This results in skb->len to exceed size for the LAST fragment at t=13 and thus a negative fragment size added to the skb.
This then crashes:
kernel BUG at include/linux/skbuff.h:2277! Oops: Exception in kernel mode, sig: 5 [#1] ... NIP [c04689f4] skb_pull+0x2c/0x48 LR [c03f62ac] gfar_clean_rx_ring+0x2e4/0x844 Call Trace: [ec4bfd38] [c06a84c4] _raw_spin_unlock_irqrestore+0x60/0x7c (unreliable) [ec4bfda8] [c03f6a44] gfar_poll_rx_sq+0x48/0xe4 [ec4bfdc8] [c048d504] __napi_poll+0x54/0x26c [ec4bfdf8] [c048d908] net_rx_action+0x138/0x2c0 [ec4bfe68] [c06a8f34] __do_softirq+0x3a4/0x4fc [ec4bfed8] [c0040150] run_ksoftirqd+0x58/0x70 [ec4bfee8] [c0066ecc] smpboot_thread_fn+0x184/0x1cc [ec4bff08] [c0062718] kthread+0x140/0x144 [ec4bff38] [c0012350] ret_from_kernel_thread+0x14/0x1c
This patch fixes this by checking for computed LAST fragment size, so a negative sized fragment is never added. In order to prevent the newer rx frame from getting corrupted, the FIRST flag is checked to discard the incomplete older frame.
Signed-off-by: Michael Braun michael-dev@fami-braun.de Signed-off-by: David S. Miller davem@davemloft.net Signed-off-by: Sasha Levin sashal@kernel.org Signed-off-by: Yang Yingliang yangyingliang@huawei.com Reviewed-by: Xiu Jianfeng xiujianfeng@huawei.com Signed-off-by: Yang Yingliang yangyingliang@huawei.com Signed-off-by: Cheng Jian cj.chengjian@huawei.com --- drivers/net/ethernet/freescale/gianfar.c | 15 +++++++++++++++ 1 file changed, 15 insertions(+)
diff --git a/drivers/net/ethernet/freescale/gianfar.c b/drivers/net/ethernet/freescale/gianfar.c index c97c4edfa31b..6e2245fdc18e 100644 --- a/drivers/net/ethernet/freescale/gianfar.c +++ b/drivers/net/ethernet/freescale/gianfar.c @@ -2942,6 +2942,10 @@ static bool gfar_add_rx_frag(struct gfar_rx_buff *rxb, u32 lstatus, if (lstatus & BD_LFLAG(RXBD_LAST)) size -= skb->len;
+ WARN(size < 0, "gianfar: rx fragment size underflow"); + if (size < 0) + return false; + skb_add_rx_frag(skb, skb_shinfo(skb)->nr_frags, page, rxb->page_offset + RXBUF_ALIGNMENT, size, GFAR_RXB_TRUESIZE); @@ -3103,6 +3107,17 @@ int gfar_clean_rx_ring(struct gfar_priv_rx_q *rx_queue, int rx_work_limit) if (lstatus & BD_LFLAG(RXBD_EMPTY)) break;
+ /* lost RXBD_LAST descriptor due to overrun */ + if (skb && + (lstatus & BD_LFLAG(RXBD_FIRST))) { + /* discard faulty buffer */ + dev_kfree_skb(skb); + skb = NULL; + rx_queue->stats.rx_dropped++; + + /* can continue normally */ + } + /* order rx buffer descriptor reads */ rmb();