ALSA: fix oops in snd_pcm_info() caused by ASoC DPCM
Unable to handle kernel NULL pointer dereference at virtual address 00000008 pgd = d5300000 [00000008] *pgd=0d265831, *pte=00000000, *ppte=00000000 Internal error: Oops: 17 [#1] PREEMPT ARM CPU: 0 PID: 2295 Comm: vlc Not tainted 3.11.0+ #755 task: dee74800 ti: e213c000 task.ti: e213c000 PC is at snd_pcm_info+0xc8/0xd8 LR is at 0x30232065 pc : [<c031b52c>] lr : [<30232065>] psr: a0070013 sp : e213dea8 ip : d81cb0d0 fp : c05f7678 r10: c05f7770 r9 : fffffdfd r8 : 00000000 r7 : d8a968a8 r6 : d8a96800 r5 : d8a96200 r4 : d81cb000 r3 : 00000000 r2 : d81cb000 r1 : 00000001 r0 : d8a96200 Flags: NzCv IRQs on FIQs on Mode SVC_32 ISA ARM Segment user Control: 10c5387d Table: 15300019 DAC: 00000015 Process vlc (pid: 2295, stack limit = 0xe213c248) [<c031b52c>] (snd_pcm_info) from [<c031b570>] (snd_pcm_info_user+0x34/0x9c) [<c031b570>] (snd_pcm_info_user) from [<c03164a4>] (snd_pcm_control_ioctl+0x274/0x280) [<c03164a4>] (snd_pcm_control_ioctl) from [<c0311458>] (snd_ctl_ioctl+0xc0/0x55c) [<c0311458>] (snd_ctl_ioctl) from [<c00eca84>] (do_vfs_ioctl+0x80/0x31c) [<c00eca84>] (do_vfs_ioctl) from [<c00ecd5c>] (SyS_ioctl+0x3c/0x60) [<c00ecd5c>] (SyS_ioctl) from [<c000e500>] (ret_fast_syscall+0x0/0x48) Code: e1a00005 e59530dc e3a01001 e1a02004 (e5933008) ---[ end trace cb3d9bdb8dfefb3c ]--- This is provoked when the ASoC front end is open along with its backend, (which causes the backend to have a runtime assigned to it) and then the SNDRV_CTL_IOCTL_PCM_INFO is requested for the (visible) backend device. Resolve this by ensuring that ASoC internal backend devices are not visible to userspace, just as the commentry for snd_pcm_new_internal() says it should be. Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk> Acked-by: Mark Brown <broonie@linaro.org> Cc: <stable@vger.kernel.org> [v3.4+] Signed-off-by: Takashi Iwai <tiwai@suse.de>
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@ -49,6 +49,8 @@ static struct snd_pcm *snd_pcm_get(struct snd_card *card, int device)
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struct snd_pcm *pcm;
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list_for_each_entry(pcm, &snd_pcm_devices, list) {
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if (pcm->internal)
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continue;
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if (pcm->card == card && pcm->device == device)
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return pcm;
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}
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@ -60,6 +62,8 @@ static int snd_pcm_next(struct snd_card *card, int device)
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struct snd_pcm *pcm;
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list_for_each_entry(pcm, &snd_pcm_devices, list) {
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if (pcm->internal)
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continue;
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if (pcm->card == card && pcm->device > device)
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return pcm->device;
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else if (pcm->card->number > card->number)
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