diff options
author | Amit Pundir <amit.pundir@linaro.org> | 2015-08-01 03:26:51 +0530 |
---|---|---|
committer | John Stultz <john.stultz@linaro.org> | 2016-02-16 13:52:12 -0800 |
commit | a89affddffb840da8d9d34c553d65dd1739e9ae1 (patch) | |
tree | 48246683e7b6ecf9c2d330db49426d809e0d92e9 /drivers/usb/gadget/function | |
parent | e931d151a9e953381f992f6da68386f1858da043 (diff) |
usb: gadget: fix NULL ptr derefer while symlinking PTP func
Fix NULL pointer dereference while trying to link PTP
function to a gadget configuration without creating
MTP function.
PTP piggyback on MTP function so make sure we have
MTP function created beforehand. Otherwise we run
into following kernel panic:
-----------------------
[ 70.329957] Unable to handle kernel NULL pointer dereference at virtual address 00000000
[ 70.330738] pgd = dd8ec000
[ 70.330916] [00000000] *pgd=00000000
[ 70.331663] Internal error: Oops: 805 [#1] SMP THUMB2
[ 70.332155] CPU: 0 PID: 2067 Comm: ln Not tainted 3.18.0-00587-gdfa582e #1
[ 70.332511] task: dd9c92c0 ti: dd822000 task.ti: dd822000
[ 70.333094] PC is at function_alloc_mtp_ptp+0xe/0x68
[ 70.333311] LR is at usb_get_function+0x11/0x1c
[ 70.333489] pc : [<c034ec12>] lr : [<c033cce9>] psr: 60070033
<..snip..>
[ 70.384111] 3fc0: bec14ae4 00000004 bec14c0a 00000053 00000004 b6f0422d 00000000 bec14adc
[ 70.384369] 3fe0: bec14af8 bec14a98 b6f071f3 b6e8977c 20070010 bec14c0d 00000000 00000000
[ 70.384832] [<c034ec12>] (function_alloc_mtp_ptp) from [<c033cce9>] (usb_get_function+0x11/0x1c)
[ 70.385146] [<c033cce9>] (usb_get_function) from [<c033da9b>] (config_usb_cfg_link+0x87/0xa8)
[ 70.385421] [<c033da9b>] (config_usb_cfg_link) from [<c011f417>] (configfs_symlink+0xb7/0x1c8)
[ 70.385696] [<c011f417>] (configfs_symlink) from [<c00dcd8d>] (vfs_symlink+0x85/0xc0)
[ 70.386010] [<c00dcd8d>] (vfs_symlink) from [<c00dce0b>] (SyS_symlinkat+0x43/0x70)
[ 70.386261] [<c00dce0b>] (SyS_symlinkat) from [<c000ce41>] (ret_fast_syscall+0x1/0x5c)
[ 70.386610] Code: eb04 4a0f 6e03 480f (e883) 0005
[ 70.387346] ---[ end trace 8dba7c552e02f8fa ]---
[ 70.387647] Kernel panic - not syncing: Fatal exception
[ 70.387980] ---[ end Kernel panic - not syncing: Fatal exception
-----------------------
Steps to reproduce the kernel panic:
mount -t configfs none /config
mkdir /config/usb_gadget/g1
cd /config/usb_gadget/g1
echo 0x18d1 > idVendor
echo 0x4e26 > idProduct
mkdir strings/0x409
echo 0123459876 > strings/0x409/serialnumber
echo Asus > strings/0x409/manufacturer
echo Nexus7 > strings/0x409/product
mkdir configs/c.1
mkdir configs/c.1/strings/0x409
echo "Conf 1" > configs/c.1/strings/0x409/configuration
echo 120 > configs/c.1/MaxPower
mkdir functions/ptp.ptp
ln -s functions/ptp.ptp configs/c.1/ptp.ptp
Also MTP and PTP are mutually exclusive functions
so make sure we have only one of it linked to a
configuration at a time. Otherwise it opens up
another set of bug(s?).
Signed-off-by: Amit Pundir <amit.pundir@linaro.org>
Diffstat (limited to 'drivers/usb/gadget/function')
-rw-r--r-- | drivers/usb/gadget/function/f_mtp.c | 18 |
1 files changed, 17 insertions, 1 deletions
diff --git a/drivers/usb/gadget/function/f_mtp.c b/drivers/usb/gadget/function/f_mtp.c index 82f6b2ebaebb..03a61f8b9d48 100644 --- a/drivers/usb/gadget/function/f_mtp.c +++ b/drivers/usb/gadget/function/f_mtp.c @@ -1426,8 +1426,24 @@ struct usb_function *function_alloc_mtp_ptp(struct usb_function_instance *fi, bool mtp_config) { struct mtp_instance *fi_mtp = to_fi_mtp(fi); - struct mtp_dev *dev = fi_mtp->dev; + struct mtp_dev *dev; + + /* + * PTP piggybacks on MTP function so make sure we have + * created MTP function before we associate this PTP + * function with a gadget configuration. + */ + if (fi_mtp->dev == NULL) { + pr_err("Error: Create MTP function before linking" + " PTP function with a gadget configuration\n"); + pr_err("\t1: Delete existing PTP function if any\n"); + pr_err("\t2: Create MTP function\n"); + pr_err("\t3: Create and symlink PTP function" + " with a gadget configuration\n"); + return NULL; + } + dev = fi_mtp->dev; dev->function.name = DRIVER_NAME; dev->function.strings = mtp_strings; if (mtp_config) { |