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Date:   Tue, 13 Jul 2021 08:59:09 +0800
From:   Peter Chen <peter.chen@kernel.org>
To:     Artur Petrosyan <Arthur.Petrosyan@synopsys.com>
Cc:     Felipe Balbi <balbi@kernel.org>,
        Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        linux-usb@vger.kernel.org, linux-kernel@vger.kernel.org,
        Grzegorz Jaszczyk <grzegorz.jaszczyk@linaro.org>,
        Thinh Nguyen <Thinh.Nguyen@synopsys.com>
Subject: Re: [PATCH v2] usb: phy: Fix page fault from usb_phy_uevent
Message-ID: <20210713005909.GA24531@nchen>
References: <c0711737fe54efa72d35df42cc4b9db31c382e7a.1625896955.git.Arthur.Petrosyan@synopsys.com>
 <20210710092247.D7AFEA005D@mailhost.synopsys.com>
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On 21-07-10 13:22:46, Artur Petrosyan wrote:
> When the dwc2 platform device is removed, it unregisters the generic
> phy. usb_remove_phy() is called and the dwc2 usb_phy is removed from the
> "phy_list", but the uevent may still attempt to get the usb_phy from the
> list, resulting in a page fault bug. Currently we can't access the usb_phy
> from the "phy_list" after the device is removed. As a fix check to make
> sure that we can get the usb_phy before moving forward with the uevent.
> 
> [   84.949345] BUG: unable to handle page fault for address:00000007935688d8
> [   84.949349] #PF: supervisor read access in kernel mode
> [   84.949351] #PF: error_code(0x0000) - not-present page
> [   84.949353] PGD 0 P4D 0
> [   84.949356] Oops: 0000 [#1] SMP PTI
> [   84.949360] CPU: 2 PID: 2081 Comm: rmmod Not tainted 5.13.0-rc4-snps-16547-ga8534cb092d7-dirty #32
> [   84.949363] Hardware name: Hewlett-Packard HP Z400 Workstation/0B4Ch, BIOS 786G3 v03.54 11/02/2011
> [   84.949365] RIP: 0010:usb_phy_uevent+0x99/0x121
> [   84.949372] Code: 8d 83 f8 00 00 00 48 3d b0 12 22 94 74 05 4c 3b 23
> 75 5b 8b 83 9c 00 00 00 be 32 00 00 00 48 8d 7c 24 04 48 c7 c2 d4 5d 7b
> 93 <48> 8b 0c c5 e0 88 56 93 e8 0f 63 8a ff 8b 83 98 00 00 00 be 32 00
> [   84.949375] RSP: 0018:ffffa46bc0f2fc70 EFLAGS: 00010246
> [   84.949378] RAX: 00000000ffffffff RBX: ffffffff942211b8 RCX: 0000000000000027
> [   84.949380] RDX: ffffffff937b5dd4 RSI: 0000000000000032 RDI: ffffa46bc0f2fc74
> [   84.949383] RBP: ffff94a306613000 R08: 0000000000000000 R09: 00000000fffeffff
> [   84.949385] R10: ffffa46bc0f2faa8 R11: ffffa46bc0f2faa0 R12: ffff94a30186d410
> [   84.949387] R13: ffff94a32d188a80 R14: ffff94a30029f960 R15: ffffffff93522dd0
> [   84.949389] FS:  00007efdbd417540(0000) GS:ffff94a513a80000(0000) knlGS:0000000000000000
> [   84.949392] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> [   84.949394] CR2: 00000007935688d8 CR3: 0000000165606000 CR4: 00000000000006e0
> [   84.949396] Call Trace:
> [   84.949401]  dev_uevent+0x190/0x1ad
> [   84.949408]  kobject_uevent_env+0x18e/0x46c
> [   84.949414]  device_release_driver_internal+0x17f/0x18e
> [   84.949418]  bus_remove_device+0xd3/0xe5
> [   84.949421]  device_del+0x1c3/0x31d
> [   84.949425]  ? kobject_put+0x97/0xa8
> [   84.949428]  platform_device_del+0x1c/0x63
> [   84.949432]  platform_device_unregister+0xa/0x11
> [   84.949436]  dwc2_pci_remove+0x1e/0x2c [dwc2_pci]
> [   84.949440]  pci_device_remove+0x31/0x81
> [   84.949445]  device_release_driver_internal+0xea/0x18e
> [   84.949448]  driver_detach+0x68/0x72
> [   84.949450]  bus_remove_driver+0x63/0x82
> [   84.949453]  pci_unregister_driver+0x1a/0x75
> [   84.949457]  __do_sys_delete_module+0x149/0x1e9
> [   84.949462]  ? task_work_run+0x64/0x6e
> [   84.949465]  ? exit_to_user_mode_prepare+0xd4/0x10d
> [   84.949471]  do_syscall_64+0x5d/0x70
> [   84.949475]  entry_SYSCALL_64_after_hwframe+0x44/0xae
> [   84.949480] RIP: 0033:0x7efdbd563bcb
> [   84.949482] Code: 73 01 c3 48 8b 0d c5 82 0c 00 f7 d8 64 89 01 48 83
> c8 ff c3 66 2e 0f 1f 84 00 00 00 00 00 90 f3 0f 1e fa b8 b0 00 00 00 0f
> 05 <48> 3d 01 f0 ff ff 73 01 c3 48 8b 0d 95 82 0c 00 f7 d8 64 89 01 48
> [   84.949485] RSP: 002b:00007ffe944d7d98 EFLAGS: 00000206 ORIG_RAX: 00000000000000b0
> [   84.949489] RAX: ffffffffffffffda RBX: 00005651072eb700 RCX: 00007efdbd563bcb
> [   84.949491] RDX: 000000000000000a RSI: 0000000000000800 RDI: 00005651072eb768
> [   84.949493] RBP: 00007ffe944d7df8 R08: 0000000000000000 R09: 0000000000000000
> [   84.949495] R10: 00007efdbd5dfac0 R11: 0000000000000206 R12: 00007ffe944d7fd0
> [   84.949497] R13: 00007ffe944d8610 R14: 00005651072eb2a0 R15: 00005651072eb700
> [   84.949500] Modules linked in: uas configfs dwc2_pci(-) phy_generic fuse crc32c_intel [last unloaded: udc_core]
> [   84.949508] CR2: 00000007935688d8
> [   84.949510] ---[ end trace e40c871ca3e4dc9e ]---
> [   84.949512] RIP: 0010:usb_phy_uevent+0x99/0x121
> 
> Fixes: a8534cb092d7 ("usb: phy: introduce usb_phy device type with its own uevent handler")
> Signed-off-by: Artur Petrosyan <Arthur.Petrosyan@synopsys.com>
> Signed-off-by: Thinh Nguyen <Thinh.Nguyen@synopsys.com>

Reviewed-by: Peter Chen <peter.chen@kernel.org>

Peter

> ---
>  Changes in v2:
>  - Updated commit message end description.
>  - Updated implementation. Now instead of checking if "phy_list" is empty, 
>    checking if we can get the usb_phy before moving forward with the uevent.
> 
>  drivers/usb/phy/phy.c | 10 ++++++++--
>  1 file changed, 8 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/usb/phy/phy.c b/drivers/usb/phy/phy.c
> index 83ed5089475a..1b24492bb4e5 100644
> --- a/drivers/usb/phy/phy.c
> +++ b/drivers/usb/phy/phy.c
> @@ -86,10 +86,10 @@ static struct usb_phy *__device_to_usb_phy(struct device *dev)
>  
>  	list_for_each_entry(usb_phy, &phy_list, head) {
>  		if (usb_phy->dev == dev)
> -			break;
> +			return usb_phy;
>  	}
>  
> -	return usb_phy;
> +	return NULL;
>  }
>  
>  static void usb_phy_set_default_current(struct usb_phy *usb_phy)
> @@ -150,8 +150,14 @@ static int usb_phy_uevent(struct device *dev, struct kobj_uevent_env *env)
>  	struct usb_phy *usb_phy;
>  	char uchger_state[50] = { 0 };
>  	char uchger_type[50] = { 0 };
> +	unsigned long flags;
>  
> +	spin_lock_irqsave(&phy_lock, flags);
>  	usb_phy = __device_to_usb_phy(dev);
> +	spin_unlock_irqrestore(&phy_lock, flags);
> +
> +	if (!usb_phy)
> +		return -ENODEV;
>  
>  	snprintf(uchger_state, ARRAY_SIZE(uchger_state),
>  		 "USB_CHARGER_STATE=%s", usb_chger_state[usb_phy->chg_state]);
> 
> base-commit: 77d34a4683b053108ecd466cc7c4193b45805528
> -- 
> 2.25.1
> 

-- 

Thanks,
Peter Chen