ALSA: seq: Fix UBSAN warning at SNDRV_SEQ_IOCTL_QUERY_NEXT_CLIENT ioctl
authorTakashi Iwai <tiwai@suse.de>
Mon, 25 Jun 2018 09:13:59 +0000 (11:13 +0200)
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>
Fri, 24 Aug 2018 11:12:32 +0000 (13:12 +0200)
commit2f483f92ce2a53b27ebead4a2ee903ec83822904
tree50d294ad3223b144938b986b462f6c9ab2f6fb32
parent8982dcff574304b26b3a22e046e08f526daa2307
ALSA: seq: Fix UBSAN warning at SNDRV_SEQ_IOCTL_QUERY_NEXT_CLIENT ioctl

[ Upstream commit c9a4c63888dbb79ce4d068ca1dd8b05bc3f156b1 ]

The kernel may spew a WARNING with UBSAN undefined behavior at
handling ALSA sequencer ioctl SNDRV_SEQ_IOCTL_QUERY_NEXT_CLIENT:

UBSAN: Undefined behaviour in sound/core/seq/seq_clientmgr.c:2007:14
signed integer overflow:
2147483647 + 1 cannot be represented in type 'int'
Call Trace:
 __dump_stack lib/dump_stack.c:77 [inline]
 dump_stack+0x122/0x1c8 lib/dump_stack.c:113
 ubsan_epilogue+0x12/0x86 lib/ubsan.c:159
 handle_overflow+0x1c2/0x21f lib/ubsan.c:190
  __ubsan_handle_add_overflow+0x2a/0x31 lib/ubsan.c:198
 snd_seq_ioctl_query_next_client+0x1ac/0x1d0 sound/core/seq/seq_clientmgr.c:2007
 snd_seq_ioctl+0x264/0x3d0 sound/core/seq/seq_clientmgr.c:2144
 ....

It happens only when INT_MAX is passed there, as we're incrementing it
unconditionally.  So the fix is trivial, check the value with
INT_MAX.  Although the bug itself is fairly harmless, it's better to
fix it so that fuzzers won't hit this again later.

Bugzilla: https://bugzilla.kernel.org/show_bug.cgi?id=200211
Signed-off-by: Takashi Iwai <tiwai@suse.de>
Signed-off-by: Sasha Levin <alexander.levin@microsoft.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
sound/core/seq/seq_clientmgr.c