linux-kernel - [PATCH] usb: gadget: composite: Fix null pointer exception

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Date:   Mon,  1 Nov 2021 09:57:57 +0800
From:   Qihang Hu <huqihang@...o.com>
To:     balbi@...nel.org, gregkh@...uxfoundation.org
Cc:     linux-usb@...r.kernel.org, linux-kernel@...r.kernel.org,
        Qihang Hu <huqihang@...o.com>
Subject: [PATCH] usb: gadget: composite: Fix null pointer exception

In the config_ep_by_speed_and_alt function, select the corresponding
descriptor through g->speed, but the interface driver may not
support the corresponding speed. So, we need to check whether the
interface driver provides the corresponding speed descriptor when
selecting the descriptor.

[  237.708146]  android_work: sent uevent USB_STATE=CONNECTED
[  237.712464]  kconfigfs-gadget gadget: super-speed config #1: b
[  237.712487]  kUnable to handle kernel NULL pointer dereference at virtual address 0000000000000000
[  237.712493]  kMem abort info:
[  237.712498]  k  ESR = 0x96000006
[  237.712504]  k  EC = 0x25: DABT (current EL), IL = 32 bits
[  237.712510]  k  SET = 0, FnV = 0
[  237.712515]  k  EA = 0, S1PTW = 0
[  237.712520]  kData abort info:
[  237.712525]  k  ISV = 0, ISS = 0x00000006
[  237.712530]  k  CM = 0, WnR = 0
[  237.712536]  kuser pgtable: 4k pages, 39-bit VAs, pgdp=000000020ef29000
[  237.712541]  k[0000000000000000] pgd=000000020ef2a003, pud=000000020ef2a003, pmd=0000000000000000
[  237.712554]  kInternal error: Oops: 96000006 [#1] PREEMPT SMP
[  237.722067]  kSkip md ftrace buffer dump for: 0x1609e0
[  237.787037]  kWorkqueue: dwc_wq dwc3_bh_work.cfi_jt
[  237.854922]  kpstate: 60c00085 (nZCv daIf +PAN +UAO)
[  237.863165]  kpc : config_ep_by_speed_and_alt+0x90/0x308
[  237.871766]  klr : audio_set_alt+0x54/0x78
[  237.879108]  ksp : ffffffc0104839e0

Signed-off-by: Qihang Hu <huqihang@...o.com>
---
 drivers/usb/gadget/composite.c | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/drivers/usb/gadget/composite.c b/drivers/usb/gadget/composite.c
index 72a9797dbbae..443a65af98af 100644
--- a/drivers/usb/gadget/composite.c
+++ b/drivers/usb/gadget/composite.c
@@ -166,21 +166,21 @@ int config_ep_by_speed_and_alt(struct usb_gadget *g,
 	/* select desired speed */
 	switch (g->speed) {
 	case USB_SPEED_SUPER_PLUS:
-		if (gadget_is_superspeed_plus(g)) {
+		if (gadget_is_superspeed_plus(g) && f->ssp_descriptors) {
 			speed_desc = f->ssp_descriptors;
 			want_comp_desc = 1;
 			break;
 		}
 		fallthrough;
 	case USB_SPEED_SUPER:
-		if (gadget_is_superspeed(g)) {
+		if (gadget_is_superspeed(g) && f->ss_descriptors) {
 			speed_desc = f->ss_descriptors;
 			want_comp_desc = 1;
 			break;
 		}
 		fallthrough;
 	case USB_SPEED_HIGH:
-		if (gadget_is_dualspeed(g)) {
+		if (gadget_is_dualspeed(g) && f->hs_descriptors) {
 			speed_desc = f->hs_descriptors;
 			break;
 		}
-- 
2.25.1