Re: Kernel Panic in skb_release_data using genet

Maxime Ripard
2022-05-13T14:57:11Z

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Hi Florian,

Sorry for reviving this old thread...

On Thu, Jun 10, 2021 at 02:33:17PM -0700, Florian Fainelli wrote:
> On 6/2/2021 6:28 AM, Maxime Ripard wrote:
> > On Tue, Jun 01, 2021 at 11:33:18AM +0200, nicolas saenz julienne wrote:
> >> On Mon, 2021-05-31 at 19:36 -0700, Florian Fainelli wrote:
> >>>> That is also how I boot my Pi4 at home, and I suspect you are right, if
> >>>> the VPU does not shut down GENET's DMA, and leaves buffer addresses in
> >>>> the on-chip descriptors that point to an address space that is managed
> >>>> totally differently by Linux, then we can have a serious problem and
> >>>> create some memory corruption when the ring is being reclaimed. I will
> >>>> run a few experiments to test that theory and there may be a solution
> >>>> using the SW_INIT reset controller to have a big reset of the controller
> >>>> before handing it over to the Linux driver.
> >>>
> >>> Adding a WARN_ON(reg & DMA_EN) in bcmgenet_dma_disable() has not shown
> >>> that the TX or RX DMA have been left running during the hand over from
> >>> the VPU to the kernel. I checked out drm-misc-next-2021-05-17 to reduce
> >>> as much as possible the differences between your set-up and my set-up
> >>> but so far have not been able to reproduce the crash in booting from NFS
> >>> repeatedly, I will try again.
> >>
> >> FWIW I can reproduce the error too. That said it's rather hard to reproduce,
> >> something in the order of 1 failure every 20 tries.
> >
> > Yeah, it looks like it's only from a cold boot and comes in "bursts",
> > where you would get like 5 in a row and be done with it for a while.
>
> Here are two patches that you could try exclusive from one another
>
> 1) Limit GENET to a single queue
>
> diff --git a/drivers/net/ethernet/broadcom/genet/bcmgenet.c
> b/drivers/net/ethernet/broadcom/genet/bcmgenet.c
> index fcca023f22e5..e400c12e6868 100644
> --- a/drivers/net/ethernet/broadcom/genet/bcmgenet.c
> +++ b/drivers/net/ethernet/broadcom/genet/bcmgenet.c
> @@ -3652,6 +3652,12 @@ static int bcmgenet_change_carrier(struct
> net_device *dev, bool new_carrier)
> return 0;
> }
>
> +static u16 bcmgenet_select_queue(struct net_device *dev, struct sk_buff
> *skb,
> + struct net_device *sb_dev)
> +{
> + return 0;
> +}
> +
> static const struct net_device_ops bcmgenet_netdev_ops = {
> .ndo_open = bcmgenet_open,
> .ndo_stop = bcmgenet_close,
> @@ -3666,6 +3672,7 @@ static const struct net_device_ops
> bcmgenet_netdev_ops = {
> #endif
> .ndo_get_stats = bcmgenet_get_stats,
> .ndo_change_carrier = bcmgenet_change_carrier,
> + .ndo_select_queue = bcmgenet_select_queue,
> };
>
> /* Array of GENET hardware parameters/characteristics */
>
> 2) Ensure that all TX/RX queues are disabled upon DMA initialization
>
> diff --git a/drivers/net/ethernet/broadcom/genet/bcmgenet.c
> b/drivers/net/ethernet/broadcom/genet/bcmgenet.c
> index fcca023f22e5..7f8a5996fbbb 100644
> --- a/drivers/net/ethernet/broadcom/genet/bcmgenet.c
> +++ b/drivers/net/ethernet/broadcom/genet/bcmgenet.c
> @@ -3237,15 +3237,21 @@ static void bcmgenet_get_hw_addr(struct
> bcmgenet_priv *priv,
> /* Returns a reusable dma control register value */
> static u32 bcmgenet_dma_disable(struct bcmgenet_priv *priv)
> {
> + unsigned int i;
> u32 reg;
> u32 dma_ctrl;
>
> /* disable DMA */
> dma_ctrl = 1 << (DESC_INDEX + DMA_RING_BUF_EN_SHIFT) | DMA_EN;
> + for (i = 0; i < priv->hw_params->tx_queues; i++)
> + dma_ctrl |= (1 << (i + DMA_RING_BUF_EN_SHIFT));
> reg = bcmgenet_tdma_readl(priv, DMA_CTRL);
> reg &= ~dma_ctrl;
> bcmgenet_tdma_writel(priv, reg, DMA_CTRL);
>
> + dma_ctrl = 1 << (DESC_INDEX + DMA_RING_BUF_EN_SHIFT) | DMA_EN;
> + for (i = 0; i < priv->hw_params->rx_queues; i++)
> + dma_ctrl |= (1 << (i + DMA_RING_BUF_EN_SHIFT));
> reg = bcmgenet_rdma_readl(priv, DMA_CTRL);
> reg &= ~dma_ctrl;
> bcmgenet_rdma_writel(priv, reg, DMA_CTRL);

It looks like current upstream still has this issue, which also upsets KASAN:

[ 16.798433] ==================================================================
[ 16.809347] BUG: KASAN: wild-memory-access in skb_release_data+0x124/0x270
[ 16.816379] Read of size 8 at addr 80800000807f2e0c by task swapper/0/0
[ 16.823122]
[ 16.824655] CPU: 0 PID: 0 Comm: swapper/0 Not tainted 5.18.0-rc5-v8+ #210
[ 16.831581] Hardware name: Raspberry Pi 4 Model B Rev 1.1 (DT)
[ 16.837525] Call trace:
[ 16.840025] dump_backtrace.part.0+0x1dc/0x1f0
[ 16.844576] show_stack+0x24/0x80
[ 16.847974] dump_stack_lvl+0x8c/0xb8
[ 16.851735] print_report+0x1cc/0x240
[ 16.855494] kasan_report+0xb4/0x120
[ 16.859161] __asan_load8+0xa0/0xc4
[ 16.862743] skb_release_data+0x124/0x270
[ 16.866849] consume_skb+0x74/0xe0
[ 16.870337] __dev_kfree_skb_any+0x74/0x90
[ 16.874538] bcmgenet_desc_rx+0x4b4/0x620
[ 16.878642] bcmgenet_rx_poll+0x78/0x150
[ 16.882657] __napi_poll.constprop.0+0x64/0x240
[ 16.887290] net_rx_action+0x4d4/0x590
[ 16.891127] __do_softirq+0x228/0x4d8
[ 16.894875] __irq_exit_rcu+0x1e4/0x24c
[ 16.898806] irq_exit_rcu+0x20/0x54
[ 16.902382] el1_interrupt+0x38/0x50
[ 16.906051] el1h_64_irq_handler+0x18/0x2c
[ 16.910250] el1h_64_irq+0x64/0x68
[ 16.913733] arch_local_irq_enable+0xc/0x20
[ 16.918010] default_idle_call+0x80/0x114
[ 16.922118] cpuidle_idle_call+0x1e0/0x224
[ 16.926310] do_idle+0x104/0x14c
[ 16.929616] cpu_startup_entry+0x34/0x3c
[ 16.933630] rest_init+0x180/0x200
[ 16.937113] arch_post_acpi_subsys_init+0x0/0x30
[ 16.941840] start_kernel+0x3c8/0x400
[ 16.945592] __primary_switched+0xa8/0xb0
[ 16.949699] ==================================================================
[ 16.957052] Disabling lock debugging due to kernel taint
[ 16.962507] Unable to handle kernel paging request at virtual address 80800000807f2e0c
[ 16.970590] Mem abort info:
[ 16.973461] ESR = 0x96000004
[ 16.976602] EC = 0x25: DABT (current EL), IL = 32 bits
[ 16.982038] SET = 0, FnV = 0
[ 16.985176] EA = 0, S1PTW = 0
[ 16.988403] FSC = 0x04: level 0 translation fault
[ 16.993440] Data abort info:
[ 16.996401] ISV = 0, ISS = 0x00000004
[ 17.000333] CM = 0, WnR = 0
[ 17.003384] [80800000807f2e0c] address between user and kernel address ranges
[ 17.010674] Internal error: Oops: 96000004 [#1] SMP
[ 17.015651] Modules linked in:
[ 17.018784] CPU: 0 PID: 0 Comm: swapper/0 Tainted: G B 5.18.0-rc5-v8+ #210
[ 17.027115] Hardware name: Raspberry Pi 4 Model B Rev 1.1 (DT)
[ 17.033052] pstate: 40000005 (nZcv daif -PAN -UAO -TCO -DIT -SSBS BTYPE=--)
[ 17.040148] pc : skb_release_data+0x124/0x270
[ 17.044603] lr : skb_release_data+0x124/0x270
[ 17.049055] sp : ffffffc00a477690
[ 17.052434] x29: ffffffc00a477690 x28: 0000000000000000 x27: ffffff8043cfeb42
[ 17.059744] x26: 0000000000000001 x25: ffffff8040a5d5be x24: 00000000ffffffff
[ 17.067049] x23: ffffff8043cfeb40 x22: 0000000000000000 x21: ffffff8040a5d540
[ 17.074355] x20: ffffff8043cfeb70 x19: 80800000807f2e04 x18: 00000000ee6397dc
[ 17.081661] x17: 0000000000000000 x16: 0000000000000000 x15: 0000000000000000
[ 17.088961] x14: 0000000000000000 x13: 746e696174206c65 x12: ffffffb801567cf9
[ 17.096265] x11: 1ffffff801567cf8 x10: ffffffb801567cf8 x9 : dfffffc000000000
[ 17.103572] x8 : ffffffc00ab3e7c7 x7 : 0000000000000001 x6 : ffffffb801567cf8
[ 17.110875] x5 : ffffffc00ab3e7c0 x4 : ffffffb801567cf9 x3 : 0000000000000000
[ 17.118178] x2 : 0000000000000020 x1 : ffffffc00a48e7c0 x0 : 0000000000000001
[ 17.125481] Call trace:
[ 17.127978] skb_release_data+0x124/0x270
[ 17.132083] consume_skb+0x74/0xe0
[ 17.135567] __dev_kfree_skb_any+0x74/0x90
[ 17.139764] bcmgenet_desc_rx+0x4b4/0x620
[ 17.143863] bcmgenet_rx_poll+0x78/0x150
[ 17.147873] __napi_poll.constprop.0+0x64/0x240
[ 17.152503] net_rx_action+0x4d4/0x590
[ 17.156338] __do_softirq+0x228/0x4d8
[ 17.160083] __irq_exit_rcu+0x1e4/0x24c
[ 17.164008] irq_exit_rcu+0x20/0x54
[ 17.167580] el1_interrupt+0x38/0x50
[ 17.171247] el1h_64_irq_handler+0x18/0x2c
[ 17.175444] el1h_64_irq+0x64/0x68
[ 17.178923] arch_local_irq_enable+0xc/0x20
[ 17.183197] default_idle_call+0x80/0x114
[ 17.187301] cpuidle_idle_call+0x1e0/0x224
[ 17.191490] do_idle+0x104/0x14c
[ 17.194793] cpu_startup_entry+0x34/0x3c
[ 17.198803] rest_init+0x180/0x200
[ 17.202283] arch_post_acpi_subsys_init+0x0/0x30
[ 17.207006] start_kernel+0x3c8/0x400
[ 17.210755] __primary_switched+0xa8/0xb0
[ 17.214872] Code: 72001c1f 540001e1 91002260 97d3086f (f9400660)
[ 17.221083] ---[ end trace 0000000000000000 ]---
[ 17.225791] Kernel panic - not syncing: Oops: Fatal exception in interrupt
[ 17.232785] SMP: stopping secondary CPUs
[ 17.236795] Kernel Offset: disabled
[ 17.240348] CPU features: 0x100,00000d08,00001086
[ 17.245143] Memory Limit: none
[ 17.248273] ---[ end Kernel panic - not syncing: Oops: Fatal exception in interrupt ]---

This is at boot, over TFTP and NFS on a RaspberryPi4

Maxime

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