RE: [PATCH v2 net] net: mscc: ocelot: unregister the PTP clock on deinit

["Y.b. Lu" <yangbo.lu@nxp.com>]

> -----Original Message-----
> From: Vladimir Oltean <olteanv@gmail.com>
> Sent: Thursday, November 28, 2019 7:24 PM
> To: davem@davemloft.net; richardcochran@gmail.com
> Cc: andrew@lunn.ch; f.fainelli@gmail.com; vivien.didelot@gmail.com;
> Claudiu Manoil <claudiu.manoil@nxp.com>; Alexandru Marginean
> <alexandru.marginean@nxp.com>; Xiaoliang Yang
> <xiaoliang.yang_1@nxp.com>; Y.b. Lu <yangbo.lu@nxp.com>;
> netdev@vger.kernel.org; alexandre.belloni@bootlin.com;
> UNGLinuxDriver@microchip.com; Vladimir Oltean
> <vladimir.oltean@nxp.com>; Antoine Tenart <antoine.tenart@bootlin.com>
> Subject: [PATCH v2 net] net: mscc: ocelot: unregister the PTP clock on deinit

[Y.b. Lu]
Acked-by: Yangbo Lu <yangbo.lu@nxp.com>

> 
> From: Vladimir Oltean <vladimir.oltean@nxp.com>
> 
> Currently a switch driver deinit frees the regmaps, but the PTP clock is still out
> there, available to user space via /dev/ptpN. Any PTP operation is a ticking
> time bomb, since it will attempt to use the freed regmaps and thus trigger
> kernel panics:
> 
> [    4.291746] fsl_enetc 0000:00:00.2 eth1: error -22 setting up slave phy
> [    4.291871] mscc_felix 0000:00:00.5: Failed to register DSA switch: -22
> [    4.308666] mscc_felix: probe of 0000:00:00.5 failed with error -22
> [    6.358270] Unable to handle kernel NULL pointer dereference at virtual
> address 0000000000000088
> [    6.367090] Mem abort info:
> [    6.369888]   ESR = 0x96000046
> [    6.369891]   EC = 0x25: DABT (current EL), IL = 32 bits
> [    6.369892]   SET = 0, FnV = 0
> [    6.369894]   EA = 0, S1PTW = 0
> [    6.369895] Data abort info:
> [    6.369897]   ISV = 0, ISS = 0x00000046
> [    6.369899]   CM = 0, WnR = 1
> [    6.369902] user pgtable: 4k pages, 48-bit VAs, pgdp=00000020d58c7000
> [    6.369904] [0000000000000088] pgd=00000020d5912003,
> pud=00000020d5915003, pmd=0000000000000000
> [    6.369914] Internal error: Oops: 96000046 [#1] PREEMPT SMP
> [    6.420443] Modules linked in:
> [    6.423506] CPU: 1 PID: 262 Comm: phc_ctl Not tainted
> 5.4.0-03625-gb7b2a5dadd7f #204
> [    6.431273] Hardware name: LS1028A RDB Board (DT)
> [    6.435989] pstate: 40000085 (nZcv daIf -PAN -UAO)
> [    6.440802] pc : css_release+0x24/0x58
> [    6.444561] lr : regmap_read+0x40/0x78
> [    6.448316] sp : ffff800010513cc0
> [    6.451636] x29: ffff800010513cc0 x28: ffff002055873040
> [    6.456963] x27: 0000000000000000 x26: 0000000000000000
> [    6.462289] x25: 0000000000000000 x24: 0000000000000000
> [    6.467617] x23: 0000000000000000 x22: 0000000000000080
> [    6.472944] x21: ffff800010513d44 x20: 0000000000000080
> [    6.478270] x19: 0000000000000000 x18: 0000000000000000
> [    6.483596] x17: 0000000000000000 x16: 0000000000000000
> [    6.488921] x15: 0000000000000000 x14: 0000000000000000
> [    6.494247] x13: 0000000000000000 x12: 0000000000000000
> [    6.499573] x11: 0000000000000000 x10: 0000000000000000
> [    6.504899] x9 : 0000000000000000 x8 : 0000000000000000
> [    6.510225] x7 : 0000000000000000 x6 : ffff800010513cf0
> [    6.515550] x5 : 0000000000000000 x4 : 0000000fffffffe0
> [    6.520876] x3 : 0000000000000088 x2 : ffff800010513d44
> [    6.526202] x1 : ffffcada668ea000 x0 : ffffcada64d8b0c0
> [    6.531528] Call trace:
> [    6.533977]  css_release+0x24/0x58
> [    6.537385]  regmap_read+0x40/0x78
> [    6.540795]  __ocelot_read_ix+0x6c/0xa0
> [    6.544641]  ocelot_ptp_gettime64+0x4c/0x110
> [    6.548921]  ptp_clock_gettime+0x4c/0x58
> [    6.552853]  pc_clock_gettime+0x5c/0xa8
> [    6.556699]  __arm64_sys_clock_gettime+0x68/0xc8
> [    6.561331]  el0_svc_common.constprop.2+0x7c/0x178
> [    6.566133]  el0_svc_handler+0x34/0xa0
> [    6.569891]  el0_sync_handler+0x114/0x1d0
> [    6.573908]  el0_sync+0x140/0x180
> [    6.577232] Code: d503201f b00119a1 91022263 b27b7be4 (f9004663)
> [    6.583349] ---[ end trace d196b9b14cdae2da ]---
> [    6.587977] Kernel panic - not syncing: Fatal exception
> [    6.593216] SMP: stopping secondary CPUs
> [    6.597151] Kernel Offset: 0x4ada54400000 from 0xffff800010000000
> [    6.603261] PHYS_OFFSET: 0xffffd0a7c0000000
> [    6.607454] CPU features: 0x10002,21806008
> [    6.611558] Memory Limit: none
> 
> And now that ocelot->ptp_clock is checked at exit, prevent a potential error
> where ptp_clock_register returned a pointer-encoded error, which we are
> keeping in the ocelot private data structure. So now,
> ocelot->ptp_clock is now either NULL or a valid pointer.
> 
> Fixes: 4e3b0468e6d7 ("net: mscc: PTP Hardware Clock (PHC) support")
> Cc: Antoine Tenart <antoine.tenart@bootlin.com>
> Reviewed-by: Florian Fainelli <f.fainelli@gmail.com>
> Signed-off-by: Vladimir Oltean <vladimir.oltean@nxp.com>
> ---
> Changes in v2:
> - Dropped the redundant check on ocelot->ptp and changed the topic of
>   the if condition.
> - Populated ocelot->ptp_clock in ocelot_init_timestamp only on valid
>   return value from ptp_clock_register, so that the deinit check can
>   never mis-trigger.
> 
>  drivers/net/ethernet/mscc/ocelot.c | 19 +++++++++++++++----
>  1 file changed, 15 insertions(+), 4 deletions(-)
> 
> diff --git a/drivers/net/ethernet/mscc/ocelot.c
> b/drivers/net/ethernet/mscc/ocelot.c
> index 52a1b1f12af8..875eea702c58 100644
> --- a/drivers/net/ethernet/mscc/ocelot.c
> +++ b/drivers/net/ethernet/mscc/ocelot.c
> @@ -2166,16 +2166,26 @@ static struct ptp_clock_info
> ocelot_ptp_clock_info = {
>  	.adjfine	= ocelot_ptp_adjfine,
>  };
> 
> +static void ocelot_deinit_timestamp(struct ocelot *ocelot) {
> +	if (ocelot->ptp_clock)
> +		ptp_clock_unregister(ocelot->ptp_clock);
> +}
> +
>  static int ocelot_init_timestamp(struct ocelot *ocelot)  {
> +	struct ptp_clock *ptp_clock;
> +
>  	ocelot->ptp_info = ocelot_ptp_clock_info;
> -	ocelot->ptp_clock = ptp_clock_register(&ocelot->ptp_info, ocelot->dev);
> -	if (IS_ERR(ocelot->ptp_clock))
> -		return PTR_ERR(ocelot->ptp_clock);
> +	ptp_clock = ptp_clock_register(&ocelot->ptp_info, ocelot->dev);
> +	if (IS_ERR(ptp_clock))
> +		return PTR_ERR(ptp_clock);
>  	/* Check if PHC support is missing at the configuration level */
> -	if (!ocelot->ptp_clock)
> +	if (!ptp_clock)
>  		return 0;
> 
> +	ocelot->ptp_clock = ptp_clock;
> +
>  	ocelot_write(ocelot, SYS_PTP_CFG_PTP_STAMP_WID(30), SYS_PTP_CFG);
>  	ocelot_write(ocelot, 0xffffffff, ANA_TABLES_PTP_ID_LOW);
>  	ocelot_write(ocelot, 0xffffffff, ANA_TABLES_PTP_ID_HIGH); @@ -2508,6
> +2518,7 @@ void ocelot_deinit(struct ocelot *ocelot)
>  	destroy_workqueue(ocelot->stats_queue);
>  	mutex_destroy(&ocelot->stats_lock);
>  	ocelot_ace_deinit();
> +	ocelot_deinit_timestamp(ocelot);
> 
>  	for (i = 0; i < ocelot->num_phys_ports; i++) {
>  		port = ocelot->ports[i];
> --
> 2.17.1