CVE-2022-48702

In the Linux kernel, the following vulnerability has been resolved:

ALSA: emu10k1: Fix out of bounds access in sndemu10k1pcmchannelalloc()

The voice allocator sometimes begins allocating from near the end of the array and then wraps around, however sndemu10k1pcmchannelalloc() accesses the newly allocated voices as if it never wrapped around.

This results in out of bounds access if the first voice has a high enough index so that firstvoice + requestedvoicecount > NUMG (64). The more voices are requested, the more likely it is for this to occur.

This was initially discovered using PipeWire, however it can be reproduced by calling aplay multiple times with 16 channels: aplay -r 48000 -D plughw:CARD=Live,DEV=3 -c 16 /dev/zero

UBSAN: array-index-out-of-bounds in sound/pci/emu10k1/emupcm.c:127:40 index 65 is out of range for type 'sndemu10k1voice [64]' CPU: 1 PID: 31977 Comm: aplay Tainted: G W IOE 6.0.0-rc2-emu10k1+ #7 Hardware name: ASUSTEK COMPUTER INC P5W DH Deluxe/P5W DH Deluxe, BIOS 3002 07/22/2010 Call Trace: <TASK> dumpstacklvl+0x49/0x63 dumpstack+0x10/0x16 ubsanepilogue+0x9/0x3f __ubsanhandleoutofbounds.cold+0x44/0x49 sndemu10k1playbackhwparams+0x3bc/0x420 [sndemu10k1] sndpcmhwparams+0x29f/0x600 [sndpcm] sndpcmcommonioctl+0x188/0x1410 [sndpcm] ? exittousermodeprepare+0x35/0x170 ? dosyscall64+0x69/0x90 ? syscallexittousermode+0x26/0x50 ? dosyscall64+0x69/0x90 ? exittousermodeprepare+0x35/0x170 sndpcmioctl+0x27/0x40 [sndpcm] __x64sysioctl+0x95/0xd0 dosyscall64+0x5c/0x90 ? dosyscall64+0x69/0x90 ? dosyscall64+0x69/0x90 entrySYSCALL64afterhwframe+0x63/0xcd