• Peter Rosin's avatar
    iio: pressure: mpl3115: do not rely on structure field ordering · a19f5fd2
    Peter Rosin authored
    commit 9cf6cdba upstream.
    
    Fixes a regression triggered by a change in the layout of
    struct iio_chan_spec, but the real bug is in the driver which assumed
    a specific structure layout in the first place. Hint: the two bits were
    not OR:ed together as implied by the indentation prior to this patch,
    there was a comma between them, which accidentally moved the ..._SCALE
    bit to the next structure field. That field was .info_mask_shared_by_type
    before the _available attributes was added by commit 51239600
    ("iio:core: add a callback to allow drivers to provide _available
    attributes") and .info_mask_separate_available afterwards, and the
    regression happened.
    
    info_mask_shared_by_type is actually a better choice than the originally
    intended info_mask_separate for the ..._SCALE bit since a constant is
    returned from mpl3115_read_raw for the scale. Using
    info_mask_shared_by_type also preserves the behavior from before the
    regression and is therefore less likely to cause other interesting side
    effects.
    
    The above mentioned regression causes an unintended sysfs attibute to
    show up that is not backed by code, in turn causing the following NULL
    pointer defererence to happen on access.
    
    Segmentation fault
    
    Unable to handle kernel NULL pointer dereference at virtual address 00000000
    pgd = ecc3c000
    [00000000] *pgd=87f91831
    Internal error: Oops: 80000007 [#1] SMP ARM
    Modules linked in:
    CPU: 1 PID: 1051 Comm: cat Not tainted 4.10.0-rc5-00009-gffd8858-dirty #3
    Hardware name: Freescale i.MX6 Quad/DualLite (Device Tree)
    task: ed54ec00 task.stack: ee2bc000
    PC is at 0x0
    LR is at iio_read_channel_info_avail+0x40/0x280
    pc : [<00000000>]    lr : [<c06fbc1c>]    psr: a0070013
    sp : ee2bdda8  ip : 00000000  fp : ee2bddf4
    r10: c0a53c74  r9 : ed79f000  r8 : ee8d1018
    r7 : 00001000  r6 : 00000fff  r5 : ee8b9a00  r4 : ed79f000
    r3 : ee2bddc4  r2 : ee2bddbc  r1 : c0a86dcc  r0 : ee8d1000
    Flags: NzCv  IRQs on  FIQs on  Mode SVC_32  ISA ARM  Segment none
    Control: 10c5387d  Table: 3cc3c04a  DAC: 00000051
    Process cat (pid: 1051, stack limit = 0xee2bc210)
    Stack: (0xee2bdda8 to 0xee2be000)
    dda0:                   ee2bddc0 00000002 c016d720 c016d394 ed54ec00 00000000
    ddc0: 60070013 ed413780 00000001 edffd480 ee8b9a00 00000fff 00001000 ee8d1018
    dde0: ed79f000 c0a53c74 ee2bde0c ee2bddf8 c0513c58 c06fbbe8 edffd480 edffd540
    de00: ee2bde3c ee2bde10 c0293474 c0513c40 c02933e4 ee2bde60 00000001 ed413780
    de20: 00000001 ed413780 00000000 edffd480 ee2bde4c ee2bde40 c0291d00 c02933f0
    de40: ee2bde9c ee2bde50 c024679c c0291ce0 edffd4b0 b6e37000 00020000 ee2bdf78
    de60: 00000000 00000000 ed54ec00 ed013200 00000817 c0a111fc edffd540 ed413780
    de80: b6e37000 00020000 00020000 ee2bdf78 ee2bded4 ee2bdea0 c0292890 c0246604
    dea0: c0117940 c016ba50 00000025 c0a111fc b6e37000 ed413780 ee2bdf78 00020000
    dec0: ee2bc000 b6e37000 ee2bdf44 ee2bded8 c021d158 c0292770 c0117764 b6e36004
    dee0: c0f0d7c4 ee2bdfb0 b6f89228 00021008 ee2bdfac ee2bdf00 c0101374 c0117770
    df00: 00000000 00000000 ee2bc000 00000000 ee2bdf34 ee2bdf20 c016ba04 c0171080
    df20: 00000000 00020000 ed413780 b6e37000 00000000 ee2bdf78 ee2bdf74 ee2bdf48
    df40: c021e7a0 c021d130 c023e300 c023e280 ee2bdf74 00000000 00000000 ed413780
    df60: ed413780 00020000 ee2bdfa4 ee2bdf78 c021e870 c021e71c 00000000 00000000
    df80: 00020000 00020000 b6e37000 00000003 c0108084 00000000 00000000 ee2bdfa8
    dfa0: c0107ee0 c021e838 00020000 00020000 00000003 b6e37000 00020000 0001a2b4
    dfc0: 00020000 00020000 b6e37000 00000003 7fffe000 00000000 00000000 00020000
    dfe0: 00000000 be98eb4c 0000c740 b6f1985c 60070010 00000003 00000000 00000000
    Backtrace:
    [<c06fbbdc>] (iio_read_channel_info_avail) from [<c0513c58>] (dev_attr_show+0x24/0x50)
     r10:c0a53c74 r9:ed79f000 r8:ee8d1018 r7:00001000 r6:00000fff r5:ee8b9a00
     r4:edffd480
    [<c0513c34>] (dev_attr_show) from [<c0293474>] (sysfs_kf_seq_show+0x90/0x110)
     r5:edffd540 r4:edffd480
    [<c02933e4>] (sysfs_kf_seq_show) from [<c0291d00>] (kernfs_seq_show+0x2c/0x30)
     r10:edffd480 r9:00000000 r8:ed413780 r7:00000001 r6:ed413780 r5:00000001
     r4:ee2bde60 r3:c02933e4
    [<c0291cd4>] (kernfs_seq_show) from [<c024679c>] (seq_read+0x1a4/0x4e0)
    [<c02465f8>] (seq_read) from [<c0292890>] (kernfs_fop_read+0x12c/0x1cc)
     r10:ee2bdf78 r9:00020000 r8:00020000 r7:b6e37000 r6:ed413780 r5:edffd540
     r4:c0a111fc
    [<c0292764>] (kernfs_fop_read) from [<c021d158>] (__vfs_read+0x34/0x118)
     r10:b6e37000 r9:ee2bc000 r8:00020000 r7:ee2bdf78 r6:ed413780 r5:b6e37000
     r4:c0a111fc
    [<c021d124>] (__vfs_read) from [<c021e7a0>] (vfs_read+0x90/0x11c)
     r8:ee2bdf78 r7:00000000 r6:b6e37000 r5:ed413780 r4:00020000
    [<c021e710>] (vfs_read) from [<c021e870>] (SyS_read+0x44/0x90)
     r8:00020000 r7:ed413780 r6:ed413780 r5:00000000 r4:00000000
    [<c021e82c>] (SyS_read) from [<c0107ee0>] (ret_fast_syscall+0x0/0x1c)
     r10:00000000 r8:c0108084 r7:00000003 r6:b6e37000 r5:00020000 r4:00020000
    Code: bad PC value
    ---[ end trace 9c4938ccd0389004 ]---
    
    Fixes: cc26ad45 ("iio: Add Freescale MPL3115A2 pressure / temperature sensor driver")
    Fixes: 51239600 ("iio:core: add a callback to allow drivers to provide _available attributes")
    Reported-by: default avatarKen Lin <ken.lin@advantech.com>
    Tested-by: default avatarKen Lin <ken.lin@advantech.com>
    Signed-off-by: default avatarPeter Rosin <peda@axentia.se>
    Signed-off-by: default avatarJonathan Cameron <jic23@kernel.org>
    Signed-off-by: default avatarBen Hutchings <ben@decadent.org.uk>
    a19f5fd2
mpl3115.c 7.77 KB