[PATCH 5.4 50/84] usb: dwc3: ep0: fix NULL pointer exception

Greg Kroah-Hartman
2021-06-14T10:59:45Z

From: Marian-Cristian Rotariu <marian.c.rotariu@gmail.com>

commit d00889080ab60051627dab1d85831cd9db750e2a upstream.

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 ]---

Signed-off-by: Marian-Cristian Rotariu <marian.c.rotariu@gmail.com>
Cc: stable <stable@vger.kernel.org>
Link: https://lore.kernel.org/r/20210608162650.58426-1-marian.c.rotariu@gmail.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
drivers/usb/dwc3/ep0.c | 3 +++
1 file changed, 3 insertions(+)

--- a/drivers/usb/dwc3/ep0.c
+++ b/drivers/usb/dwc3/ep0.c
@@ -292,6 +292,9 @@ static struct dwc3_ep *dwc3_wIndex_to_de
epnum |= 1;

dep = dwc->eps[epnum];
+ if (dep == NULL)
+ return NULL;
+
if (dep->flags & DWC3_EP_ENABLED)
return dep;