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From: "Schmid, Carsten" <>
To: Hans de Goede <>
Cc: "" <>,
	"" <>,
	"" <>
Subject: AW: [PATCH] usb: xhci-pci: reorder removal to avoid use-after-free
Date: Wed, 14 Aug 2019 13:32:49 +0000
Message-ID: <> (raw)
In-Reply-To: <>

> > On driver removal, the platform_device_unregister call
> > attached through devm_add_action_or_reset was executed
> > after usb_hcd_pci_remove.
> > This lead to a use-after-free for the iomem resorce of
> > the xhci-ext-caps driver in the platform removal
> > because the parent of the resource was freed earlier.
> >
> > Fix this by reordering of the removal sequence.
> >
> > Signed-off-by: Carsten Schmid <>
> Assuming this has been tested, overal this looks good to me.

Tested on 4.14.129, ported to v5.2.7, compiled there.

> But there are 2 things to fix:
> 1) Maybe pick a more descriptive struct member name then pdev.
>     pdev with pci-devices often points to a pci_device ...
>     How about: role_switch_pdev ?

Ok, good point. Had platform dev pdev in mind ...

> 2) xhci_ext_cap_init() is not the last call which can fail in
>     xhci_pci_probe(), since you now no longer use
> devm_add_action_or_reset
>     for auto-cleanup, you must now manually cleanup by calling
>     xhci_ext_cap_remove() when later steps of xhci_pci_probe() fail.
>     it looks like you will need a new ext_cap_remove error-exit label
>     for this put above the put_usb3_hcd label and goto this new label
>     instead of to put_usb3_hcd in all error paths after a successful call
>     to xhci_ext_cap_init()

Right. Will review this path and correct accordingly.

Maybe an additional label isn't required because pdev is only set when
xhci_ext_cap_init created the platform device, and xhci_ext_cap_remove
checks for pdev being set.
So a call to xhci_ext_cap_remove doesn't harm if pdev is not set up yet.
But for readability it might be better to create a label.

Best regards

  reply index

Thread overview: 6+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-08-14 11:39 Schmid, Carsten
2019-08-14 12:54 ` Hans de Goede
2019-08-14 13:32   ` Schmid, Carsten [this message]
2019-08-14 13:36     ` AW: " Hans de Goede
2019-08-14 14:32       ` [PATCH v2] " Schmid, Carsten
2019-08-15 15:27         ` Hans de Goede

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