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Subject: Re: [PATCH net-next v2 1/3] net: phy: xgmiitorgmii: Check phy_driver
 ready before accessing
To:     Brandon Maier <brandon.maier@rockwellcollins.com>,
        netdev@vger.kernel.org
Cc:     andrew@lunn.ch, davem@davemloft.net, michal.simek@xilinx.com,
        clayton.shotwell@rockwellcollins.com,
        kristopher.cory@rockwellcollins.com, linux-kernel@vger.kernel.org
References: <20180626175050.71165-1-brandon.maier@rockwellcollins.com>
From:   Florian Fainelli <f.fainelli@gmail.com>
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Message-ID: <6387da90-c0de-00d9-9744-d4386a316e79@gmail.com>
Date:   Tue, 26 Jun 2018 14:59:29 -0700
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In-Reply-To: <20180626175050.71165-1-brandon.maier@rockwellcollins.com>
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On 06/26/2018 10:50 AM, Brandon Maier wrote:
> Since a phy_device is added to the global mdio_bus list during
> phy_device_register(), but a phy_device's phy_driver doesn't get
> attached until phy_probe(). It's possible of_phy_find_device() in
> xgmiitorgmii will return a valid phy with a NULL phy_driver. Leading to
> a NULL pointer access during the memcpy().
> 
> Fixes this Oops:
> 
> Unable to handle kernel NULL pointer dereference at virtual address 00000000
> pgd = c0004000
> [00000000] *pgd=00000000
> Internal error: Oops: 5 [#1] PREEMPT SMP ARM
> Modules linked in:
> CPU: 0 PID: 1 Comm: swapper/0 Not tainted 4.14.40 #1
> Hardware name: Xilinx Zynq Platform
> task: ce4c8d00 task.stack: ce4ca000
> PC is at memcpy+0x48/0x330
> LR is at xgmiitorgmii_probe+0x90/0xe8
> pc : [<c074bc68>]    lr : [<c0529548>]    psr: 20000013
> sp : ce4cbb54  ip : 00000000  fp : ce4cbb8c
> r10: 00000000  r9 : 00000000  r8 : c0c49178
> r7 : 00000000  r6 : cdc14718  r5 : ce762800  r4 : cdc14710
> r3 : 00000000  r2 : 00000054  r1 : 00000000  r0 : cdc14718
> Flags: nzCv  IRQs on  FIQs on  Mode SVC_32  ISA ARM  Segment none
> Control: 18c5387d  Table: 0000404a  DAC: 00000051
> Process swapper/0 (pid: 1, stack limit = 0xce4ca210)
> ...
> [<c074bc68>] (memcpy) from [<c0529548>] (xgmiitorgmii_probe+0x90/0xe8)
> [<c0529548>] (xgmiitorgmii_probe) from [<c0526a94>] (mdio_probe+0x28/0x34)
> [<c0526a94>] (mdio_probe) from [<c04db98c>] (driver_probe_device+0x254/0x414)
> [<c04db98c>] (driver_probe_device) from [<c04dbd58>] (__device_attach_driver+0xac/0x10c)
> [<c04dbd58>] (__device_attach_driver) from [<c04d96f4>] (bus_for_each_drv+0x84/0xc8)
> [<c04d96f4>] (bus_for_each_drv) from [<c04db5bc>] (__device_attach+0xd0/0x134)
> [<c04db5bc>] (__device_attach) from [<c04dbdd4>] (device_initial_probe+0x1c/0x20)
> [<c04dbdd4>] (device_initial_probe) from [<c04da8fc>] (bus_probe_device+0x98/0xa0)
> [<c04da8fc>] (bus_probe_device) from [<c04d8660>] (device_add+0x43c/0x5d0)
> [<c04d8660>] (device_add) from [<c0526cb8>] (mdio_device_register+0x34/0x80)
> [<c0526cb8>] (mdio_device_register) from [<c0580b48>] (of_mdiobus_register+0x170/0x30c)
> [<c0580b48>] (of_mdiobus_register) from [<c05349c4>] (macb_probe+0x710/0xc00)
> [<c05349c4>] (macb_probe) from [<c04dd700>] (platform_drv_probe+0x44/0x80)
> [<c04dd700>] (platform_drv_probe) from [<c04db98c>] (driver_probe_device+0x254/0x414)
> [<c04db98c>] (driver_probe_device) from [<c04dbc58>] (__driver_attach+0x10c/0x118)
> [<c04dbc58>] (__driver_attach) from [<c04d9600>] (bus_for_each_dev+0x8c/0xd0)
> [<c04d9600>] (bus_for_each_dev) from [<c04db1fc>] (driver_attach+0x2c/0x30)
> [<c04db1fc>] (driver_attach) from [<c04daa98>] (bus_add_driver+0x50/0x260)
> [<c04daa98>] (bus_add_driver) from [<c04dc440>] (driver_register+0x88/0x108)
> [<c04dc440>] (driver_register) from [<c04dd6b4>] (__platform_driver_register+0x50/0x58)
> [<c04dd6b4>] (__platform_driver_register) from [<c0b31248>] (macb_driver_init+0x24/0x28)
> [<c0b31248>] (macb_driver_init) from [<c010203c>] (do_one_initcall+0x60/0x1a4)
> [<c010203c>] (do_one_initcall) from [<c0b00f78>] (kernel_init_freeable+0x15c/0x1f8)
> [<c0b00f78>] (kernel_init_freeable) from [<c0763d10>] (kernel_init+0x18/0x124)
> [<c0763d10>] (kernel_init) from [<c0112d74>] (ret_from_fork+0x14/0x20)
> Code: ba000002 f5d1f03c f5d1f05c f5d1f07c (e8b151f8)
> ---[ end trace 3e4ec21905820a1f ]---
> 
> Signed-off-by: Brandon Maier <brandon.maier@rockwellcollins.com>

Reviewed-by: Florian Fainelli <f.fainelli@gmail.com>
-- 
Florian