In older versions of the IIO framework it was possible to pass a completely
different set of channels to iio_buffer_register() as the one that is
assigned to the IIO device. Commit 959d2952d1 ("staging:iio: make
iio_sw_buffer_preenable much more general.") introduced a restriction that
requires that the set of channels that is passed to iio_buffer_register() is
a subset of the channels assigned to the IIO device as the IIO core will use
the list of channels that is assigned to the device to lookup a channel by
scan index in iio_compute_scan_bytes(). If it can not find the channel the
function will crash. This patch fixes the issue by making sure that the same
set of channels is assigned to the IIO device and passed to
iio_buffer_register().
Note that we need to remove the IIO_CHAN_INFO_RAW and IIO_CHAN_INFO_SCALE
info attributes from the channels since we don't actually want those to be
registered.
Fixes the following crash:
Unable to handle kernel NULL pointer dereference at virtual address 00000016
pgd = d2094000
[00000016] *pgd=16e39831, *pte=00000000, *ppte=00000000
Internal error: Oops: 17 [#1] PREEMPT SMP ARM
Modules linked in:
CPU: 1 PID: 1695 Comm: bash Not tainted 3.17.0-06329-g29461ee #9686
task: d7768040 ti: d5bd4000 task.ti: d5bd4000
PC is at iio_compute_scan_bytes+0x38/0xc0
LR is at iio_compute_scan_bytes+0x34/0xc0
pc : [<c0316de8>] lr : [<c0316de4>] psr: 60070013
sp : d5bd5ec0 ip : 00000000 fp : 00000000
r10: d769f934 r9 : 00000000 r8 : 00000001
r7 : 00000000 r6 : c8fc6240 r5 : d769f800 r4 : 00000000
r3 : d769f800 r2 : 00000000 r1 : ffffffff r0 : 00000000
Flags: nZCv IRQs on FIQs on Mode SVC_32 ISA ARM Segment user
Control: 18c5387d Table: 1209404a DAC: 00000015
Process bash (pid: 1695, stack limit = 0xd5bd4240)
Stack: (0xd5bd5ec0 to 0xd5bd6000)
5ec0: d769f800 d7435640 c8fc6240 d769f984 00000000 c03175a4 d7435690 d7435640
5ee0: d769f990 00000002 00000000 d769f800 d5bd4000 00000000 000b43a8 c03177f4
5f00: d769f810 0162b8c8 00000002 c8fc7e00 d77f1d08 d77f1da8 c8fc7e00 c01faf1c
5f20: 00000002 c010694c c010690c d5bd5f88 00000002 c8fc6840 c8fc684c c0105e08
5f40: 00000000 00000000 d20d1580 00000002 000af408 d5bd5f88 c000de84 c00b76d4
5f60: d20d1580 000af408 00000002 d20d1580 d20d1580 00000002 000af408 c000de84
5f80: 00000000 c00b7a44 00000000 00000000 00000002 b6ebea78 00000002 000af408
5fa0: 00000004 c000dd00 b6ebea78 00000002 00000001 000af408 00000002 00000000
5fc0: b6ebea78 00000002 000af408 00000004 bee96a4c 000a6094 00000000 000b43a8
5fe0: 00000000 bee969cc b6e2eb77 b6e6525c 40070010 00000001 00000000 00000000
[<c0316de8>] (iio_compute_scan_bytes) from [<c03175a4>] (__iio_update_buffers+0x248/0x438)
[<c03175a4>] (__iio_update_buffers) from [<c03177f4>] (iio_buffer_store_enable+0x60/0x7c)
[<c03177f4>] (iio_buffer_store_enable) from [<c01faf1c>] (dev_attr_store+0x18/0x24)
[<c01faf1c>] (dev_attr_store) from [<c010694c>] (sysfs_kf_write+0x40/0x4c)
[<c010694c>] (sysfs_kf_write) from [<c0105e08>] (kernfs_fop_write+0x110/0x154)
[<c0105e08>] (kernfs_fop_write) from [<c00b76d4>] (vfs_write+0xbc/0x170)
[<c00b76d4>] (vfs_write) from [<c00b7a44>] (SyS_write+0x40/0x78)
[<c00b7a44>] (SyS_write) from [<c000dd00>] (ret_fast_syscall+0x0/0x30)
Fixes: 959d2952d1 ("staging:iio: make iio_sw_buffer_preenable much more general.")
Signed-off-by: Lars-Peter Clausen <lars@metafoo.de>
Cc: <stable@vger.kernel.org>
Signed-off-by: Jonathan Cameron <jic23@kernel.org>
e10554738c