patch "usb: dwc3: ep0: fix NULL pointer exception" added to usb-linus

This is a note to let you know that I've just added the patch titled

usb: dwc3: ep0: fix NULL pointer exception

to my usb git tree which can be found at
git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/usb.git
in the usb-linus branch.

The patch will show up in the next release of the linux-next tree (usually sometime within the next 24 hours during the week.)

The patch will hopefully also be merged in Linus's tree for the next -rc kernel release.

If you have any questions about this process, please let me know.

From d00889080ab60051627dab1d85831cd9db750e2a Mon Sep 17 00:00:00 2001
From: Marian-Cristian Rotariu <[email protected]>
Date: Tue, 8 Jun 2021 19:26:50 +0300
Subject: usb: dwc3: ep0: fix NULL pointer exception

There is no validation of the index from dwc3_wIndex_to_dep() and we might be referring a non-existing ep and trigger a NULL pointer exception. In certain configurations we might use fewer eps and the index might wrongly indicate a larger ep index than existing.

By adding this validation from the patch we can actually report a wrong index back to the caller.

In our usecase we are using a composite device on an older kernel, but upstream might use this fix also. Unfortunately, I cannot describe the hardware for others to reproduce the issue as it is a proprietary implementation.

[   82.958261] Unable to handle kernel NULL pointer dereference at virtual address 00000000000000a4
[   82.966891] Mem abort info:
[   82.969663]   ESR = 0x96000006
[   82.972703]   Exception class = DABT (current EL), IL = 32 bits
[   82.978603]   SET = 0, FnV = 0
[   82.981642]   EA = 0, S1PTW = 0
[   82.984765] Data abort info:
[   82.987631]   ISV = 0, ISS = 0x00000006
[   82.991449]   CM = 0, WnR = 0
[   82.994409] user pgtable: 4k pages, 39-bit VAs, pgdp = 00000000c6210ccc
[   83.000999] [00000000000000a4] pgd=0000000053aa5003, pud=0000000053aa5003, pmd=0000000000000000
[   83.009685] Internal error: Oops: 96000006 [#1] PREEMPT SMP
[   83.026433] Process irq/62-dwc3 (pid: 303, stack limit = 0x000000003985154c)
[   83.033470] CPU: 0 PID: 303 Comm: irq/62-dwc3 Not tainted 4.19.124 #1
[   83.044836] pstate: 60000085 (nZCv daIf -PAN -UAO)
[   83.049628] pc : dwc3_ep0_handle_feature+0x414/0x43c
[   83.054558] lr : dwc3_ep0_interrupt+0x3b4/0xc94

...

[   83.141788] Call trace:
[   83.144227]  dwc3_ep0_handle_feature+0x414/0x43c
[   83.148823]  dwc3_ep0_interrupt+0x3b4/0xc94
[   83.181546] ---[ end trace aac6b5267d84c32f ]---

---
 drivers/usb/dwc3/ep0.c | 3 +++
 1 file changed, 3 insertions(+)

index 8b668ef46f7f..3cd294264372 100644
@@ -292,6 +292,9 @@ static struct dwc3_ep *dwc3_wIndex_to_dep(struct dwc3 *dwc, __le16 wIndex_le)
 		epnum |= 1;
 
 	dep = dwc->eps[epnum];
+	if (dep == NULL)
+		return NULL;
+
 	if (dep->flags & DWC3_EP_ENABLED)
 		return dep;
 

2.32.0