Skip to contentSkip to conversation

New: Possible null pointer dereference in ohci_restart()

Bug 207125 [email protected] 1 participant 6 messages Apr 5, 2020 – Apr 6, 2020 USB

lore
Share & tools
lore

[email protected]

author
#0 lore raw

https://bugzilla.kernel.org/show_bug.cgi?id=207125

Bug ID: 207125
Summary: Possible null pointer dereference in ohci_restart()
Product: Drivers
Version: 2.5
Kernel Version: Linux 4.17
Hardware: All
OS: Linux
Tree: Mainline
Status: NEW
Severity: normal
Priority: P1
Component: USB
Assignee: [email protected]
Reporter: [email protected]
Regression: No

In Linux 4.17, ohci_restart() in /drivers/usb/host/ohci-hcd.c does not handle the failure of ohci_init(), causing ohci->hcca could be a null pointer. After that, writting to this ohci->hcca->int_table [i] field could cause a null pointer dereference bug.

Url of ohci_restart()
https://elixir.bootlin.com/linux/v4.10.17/source/drivers/usb/host/ohci-hcd.c#L1000

int ohci_restart(struct ohci_hcd *ohci)

{
        ...
        ohci_init(ohci); //does not handle the failure
        ...
        for (i = 0; i < NUM_INTS; i++) ohci->hcca->int_table [i] = 0; //null
pointer dereference
        ...
}

Url of ohci_init()
https://elixir.bootlin.com/linux/v4.10.17/source/drivers/usb/host/ohci-hcd.c#L441
static int ohci_init (struct ohci_hcd *ohci) {
...
ohci->hcca = dma_alloc_coherent (hcd->self.controller,

                        sizeof(*ohci->hcca), &ohci->hcca_dma, GFP_KERNEL);
        if (!ohci->hcca)
                return -ENOMEM; // ohci->hcca can be a null pointer

...
}

Signature · 2 lines
You are receiving this mail because:
You are watching the assignee of the bug.
author
#1 lore raw

[Bug 207125] Possible null pointer dereference in ohci_restart()

https://bugzilla.kernel.org/show_bug.cgi?id=207125

Alan Stern ([email protected]) changed:

What |Removed |Added
----------------------------------------------------------------------------
CC| |[email protected]

--- Comment #1 from Alan Stern ([email protected]) --- This is not a bug. When ohci_restart() calls ohci_init(), ohci->hcca has already been initialized to a non-NULL value. Therefore the -ENOMEM return cannot happen.

Signature · 2 lines
You are receiving this mail because:
You are watching the assignee of the bug.
author
#2 lore raw

[Bug 207125] Possible null pointer dereference in ohci_restart()

In reply to [email protected]

https://bugzilla.kernel.org/show_bug.cgi?id=207125

--- Comment #2 from Dongyang Zhan ([email protected]) --- (In reply to Alan Stern from comment #1)

Quoted 3 lines

This is not a bug. When ohci_restart() calls ohci_init(), ohci->hcca has already been initialized to a non-NULL value. Therefore the -ENOMEM return cannot happen.

ohci->hcca will be allocated again in the ohci_init() Could it fail in that function?

Signature · 2 lines
You are receiving this mail because:
You are watching the assignee of the bug.
author
#3 lore raw

[Bug 207125] Possible null pointer dereference in ohci_restart()

In reply to [email protected]

https://bugzilla.kernel.org/show_bug.cgi?id=207125

--- Comment #3 from Dongyang Zhan ([email protected]) --- (In reply to Alan Stern from comment #1)

Quoted 3 lines

This is not a bug. When ohci_restart() calls ohci_init(), ohci->hcca has already been initialized to a non-NULL value. Therefore the -ENOMEM return cannot happen.

I mean could you tell me where ohci->hcca is initialized before ohci_restart()?

Signature · 2 lines
You are receiving this mail because:
You are watching the assignee of the bug.
author
#5 lore raw

[Bug 207125] Possible null pointer dereference in ohci_restart()

In reply to [email protected]

https://bugzilla.kernel.org/show_bug.cgi?id=207125

Dongyang Zhan ([email protected]) changed:

What |Removed |Added
----------------------------------------------------------------------------

             Status|NEW                         |RESOLVED
         Resolution|---                         |WILL_NOT_FIX

--- Comment #5 from Dongyang Zhan ([email protected]) --- (In reply to Alan Stern from comment #4)

Quoted 2 lines

ohci->hcca is initialized when ohci_setup() calls ohci_init(). This happens long before ohci_restart() will ever get called.

Thank you so much.

Signature · 2 lines
You are receiving this mail because:
You are watching the assignee of the bug.