linux/include
Takashi Iwai a91d66129f ALSA: hda - Fix incorrect TLV callback check introduced during set_fs() removal
The commit 99b5c5bb9a ("ALSA: hda - Remove the use of set_fs()")
converted the get_kctl_0dB_offset() call for killing set_fs() usage in
HD-audio codec code.  The conversion assumed that the TLV callback
used in HD-audio code is only snd_hda_mixer_amp() and applies the TLV
calculation locally.

Although this assumption is correct, and all slave kctls are actually
with that callback, the current code is still utterly buggy; it
doesn't hit this condition and falls back to the next check.  It's
because the function gets called after adding slave kctls to vmaster.
By assigning a slave kctl, the slave kctl object is faked inside
vmaster code, and the whole kctl ops are overridden.  Thus the
callback op points to a different value from what we've assumed.

More badly, as reported by the KERNEXEC and UDEREF features of PaX,
the code flow turns into the unexpected pitfall.  The next fallback
check is SNDRV_CTL_ELEM_ACCESS_TLV_READ access bit, and this always
hits for each kctl with TLV.  Then it evaluates the callback function
pointer wrongly as if it were a TLV array.  Although currently its
side-effect is fairly limited, this incorrect reference may lead to an
unpleasant result.

For addressing the regression, this patch introduces a new helper to
vmaster code, snd_ctl_apply_vmaster_slaves().  This works similarly
like the existing map_slaves() in hda_codec.c: it loops over the slave
list of the given master, and applies the given function to each
slave.  Then the initializer function receives the right kctl object
and we can compare the correct pointer instead of the faked one.

Also, for catching the similar breakage in future, give an error
message when the unexpected TLV callback is found and bail out
immediately.

Fixes: 99b5c5bb9a ("ALSA: hda - Remove the use of set_fs()")
Reported-by: PaX Team <pageexec@freemail.hu>
Cc: <stable@vger.kernel.org> # v4.13
Signed-off-by: Takashi Iwai <tiwai@suse.de>
2017-10-18 12:27:00 +02:00
..
acpi ACPI / bus: Make ACPI_HANDLE() work for non-GPL code again 2017-09-19 22:42:31 +02:00
asm-generic percpu: make this_cpu_generic_read() atomic w.r.t. interrupts 2017-09-26 07:37:33 -07:00
clocksource
crypto
drm lib/interval_tree: fast overlap detection 2017-09-08 18:26:49 -07:00
dt-bindings ARC: reset: remove the misleading v1 suffix all over 2017-09-18 13:02:03 +02:00
keys
kvm
linux MMC core: 2017-10-07 10:03:03 -07:00
math-emu
media media updates for v4.14-rc1 2017-09-07 12:53:14 -07:00
memory
misc
net udp: perform source validation for mcast early demux 2017-10-01 03:55:47 +01:00
pcmcia
ras
rdma IB: Correct MR length field to be 64-bit 2017-09-25 11:47:23 -04:00
scsi scsi: libiscsi: Remove iscsi_destroy_session 2017-10-02 22:23:21 -04:00
soc ARM: SoC driver updates for v4.14 2017-09-10 20:40:00 -07:00
sound ALSA: hda - Fix incorrect TLV callback check introduced during set_fs() removal 2017-10-18 12:27:00 +02:00
target
trace sched/debug: Add explicit TASK_PARKED printing 2017-09-29 11:02:57 +02:00
uapi - A stable fix for the alignment of the event number reported at the 2017-10-05 15:17:40 -07:00
video
xen xen, arm64: drop dummy lookup_address() 2017-09-19 09:25:05 -04:00