Currently, there's no guarantee that udc->driver
will be valid when using soft_connect sysfs
interface. In fact, we can very easily trigger
a NULL pointer dereference by trying to disconnect
when a gadget driver isn't loaded.
Fix this bug:
~# echo disconnect > soft_connect
[ 33.685743] Unable to handle kernel NULL pointer dereference at virtual address 00000014
[ 33.694221] pgd = ed0cc000
[ 33.697174] [00000014] *pgd=ae351831, *pte=00000000, *ppte=00000000
[ 33.703766] Internal error: Oops: 17 [#1] SMP ARM
[ 33.708697] Modules linked in: xhci_plat_hcd xhci_hcd snd_soc_davinci_mcasp snd_soc_tlv320aic3x snd_soc_edma snd_soc_omap snd_soc_evm snd_soc_core dwc3 snd_compress snd_pcm_dmaengine snd_pcm snd_timer snd lis3lv02d_i2c matrix_keypad lis3lv02d dwc3_omap input_polldev soundcore
[ 33.734372] CPU: 0 PID: 1457 Comm: bash Not tainted 3.17.0-09740-ga93416e-dirty #345
[ 33.742457] task: ee71ce00 ti: ee68a000 task.ti: ee68a000
[ 33.748116] PC is at usb_udc_softconn_store+0xa4/0xec
[ 33.753416] LR is at mark_held_locks+0x78/0x90
[ 33.758057] pc : [<c04df128>] lr : [<c00896a4>] psr: 20000013
[ 33.758057] sp : ee68bec8 ip : c0c00008 fp : ee68bee4
[ 33.770050] r10: ee6b394c r9 : ee68bf80 r8 : ee6062c0
[ 33.775508] r7 : 00000000 r6 : ee6062c0 r5 : 0000000b r4 : ee739408
[ 33.782346] r3 : 00000000 r2 : 00000000 r1 : ee71d390 r0 : ee664170
[ 33.789168] Flags: nzCv IRQs on FIQs on Mode SVC_32 ISA ARM Segment user
[ 33.796636] Control: 10c5387d Table: ad0cc059 DAC: 00000015
[ 33.802638] Process bash (pid: 1457, stack limit = 0xee68a248)
[ 33.808740] Stack: (0xee68bec8 to 0xee68c000)
[ 33.813299] bec0: 0000000b c0411284 ee6062c0 00000000 ee68bef4 ee68bee8
[ 33.821862] bee0: c04112ac c04df090 ee68bf14 ee68bef8 c01c2868 c0411290 0000000b ee6b3940
[ 33.830419] bf00: 00000000 00000000 ee68bf4c ee68bf18 c01c1a24 c01c2818 00000000 00000000
[ 33.838990] bf20: ee61b940 ee2f47c0 0000000b 000ce408 ee68bf80 c000f304 ee68a000 00000000
[ 33.847544] bf40: ee68bf7c ee68bf50 c0152dd8 c01c1960 ee68bf7c c0170af8 ee68bf7c ee2f47c0
[ 33.856099] bf60: ee2f47c0 000ce408 0000000b c000f304 ee68bfa4 ee68bf80 c0153330 c0152d34
[ 33.864653] bf80: 00000000 00000000 0000000b 000ce408 b6e7fb50 00000004 00000000 ee68bfa8
[ 33.873204] bfa0: c000f080 c01532e8 0000000b 000ce408 00000001 000ce408 0000000b 00000000
[ 33.881763] bfc0: 0000000b 000ce408 b6e7fb50 00000004 0000000b 00000000 000c5758 00000000
[ 33.890319] bfe0: 00000000 bec2c924 b6de422d b6e1d226 40000030 00000001 75716d2f 00657565
[ 33.898890] [<c04df128>] (usb_udc_softconn_store) from [<c04112ac>] (dev_attr_store+0x28/0x34)
[ 33.907920] [<c04112ac>] (dev_attr_store) from [<c01c2868>] (sysfs_kf_write+0x5c/0x60)
[ 33.916200] [<c01c2868>] (sysfs_kf_write) from [<c01c1a24>] (kernfs_fop_write+0xd0/0x194)
[ 33.924773] [<c01c1a24>] (kernfs_fop_write) from [<c0152dd8>] (vfs_write+0xb0/0x1bc)
[ 33.932874] [<c0152dd8>] (vfs_write) from [<c0153330>] (SyS_write+0x54/0xb0)
[ 33.940247] [<c0153330>] (SyS_write) from [<c000f080>] (ret_fast_syscall+0x0/0x48)
[ 33.948160] Code: e1a01007 e12fff33 e5140004 e5143008 (e5933014)
[ 33.954625] ---[ end trace f849bead94eab7ea ]---
Fixes: 2ccea03 (usb: gadget: introduce UDC Class)
Cc: <stable@xxxxxxxxxxxxxxx> # v3.1+
Signed-off-by: Felipe Balbi <balbi@xxxxxx>
---
drivers/usb/gadget/udc/udc-core.c | 5 +++++
1 file changed, 5 insertions(+)
diff --git a/drivers/usb/gadget/udc/udc-core.c b/drivers/usb/gadget/udc/udc-core.c
index f107bb6..f205465 100644
--- a/drivers/usb/gadget/udc/udc-core.c
+++ b/drivers/usb/gadget/udc/udc-core.c
@@ -507,6 +507,11 @@ static ssize_t usb_udc_softconn_store(struct device *dev,
{
struct usb_udc *udc = container_of(dev, struct usb_udc, dev);
+ if (!udc->driver) {
+ dev_err(dev, "soft-connect without a gadget driver\n");
+ return -EOPNOTSUPP;
+ }
+
if (sysfs_streq(buf, "connect")) {
usb_gadget_udc_start(udc->gadget, udc->driver);
usb_gadget_connect(udc->gadget);
--
2.1.0.GIT
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