From: Takashi Iwai <tiwai@suse.de> stable inclusion from stable-v6.6.70 commit d2392b79d8af3714ea8878b71c66dc49d3110f44 category: bugfix bugzilla: https://gitee.com/src-openeuler/kernel/issues/IBID2T CVE: CVE-2024-57893 Reference: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=... -------------------------------- commit 0179488ca992d79908b8e26b9213f1554fc5bacc upstream. OSS sequencer handles the SysEx messages split in 6 bytes packets, and ALSA sequencer OSS layer tries to combine those. It stores the data in the internal buffer and this access is racy as of now, which may lead to the out-of-bounds access. As a temporary band-aid fix, introduce a mutex for serializing the process of the SysEx message packets. Reported-by: Kun Hu <huk23@m.fudan.edu.cn> Closes: https://lore.kernel.org/2B7E93E4-B13A-4AE4-8E87-306A8EE9BBB7@m.fudan.edu.cn Cc: <stable@vger.kernel.org> Link: https://patch.msgid.link/20241230110543.32454-1-tiwai@suse.de Signed-off-by: Takashi Iwai <tiwai@suse.de> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> Conflicts: sound/core/seq/oss/seq_oss_synth.c [Commit 54da6a092431("locking: Introduce __cleanup() based infrastructure") not merged, The guard() function is not introduced.] Signed-off-by: Gu Bowen <gubowen5@huawei.com> --- sound/core/seq/oss/seq_oss_synth.c | 23 +++++++++++++++++------ 1 file changed, 17 insertions(+), 6 deletions(-) diff --git a/sound/core/seq/oss/seq_oss_synth.c b/sound/core/seq/oss/seq_oss_synth.c index c93945917235..33dbe0223326 100644 --- a/sound/core/seq/oss/seq_oss_synth.c +++ b/sound/core/seq/oss/seq_oss_synth.c @@ -79,6 +79,7 @@ static struct seq_oss_synth midi_synth_dev = { }; static DEFINE_SPINLOCK(register_lock); +static DEFINE_MUTEX(sysex_mutex); /* * prototypes @@ -504,16 +505,20 @@ snd_seq_oss_synth_sysex(struct seq_oss_devinfo *dp, int dev, unsigned char *buf, unsigned char *dest; struct seq_oss_synth_sysex *sysex; struct seq_oss_synthinfo *info; + int err = -EINVAL; info = snd_seq_oss_synth_info(dp, dev); if (!info) return -ENXIO; + mutex_lock(&sysex_mutex); sysex = info->sysex; if (sysex == NULL) { sysex = kzalloc(sizeof(*sysex), GFP_KERNEL); - if (sysex == NULL) - return -ENOMEM; + if (sysex == NULL) { + err = -ENOMEM; + goto unlock_sysex; + } info->sysex = sysex; } @@ -538,19 +543,25 @@ snd_seq_oss_synth_sysex(struct seq_oss_devinfo *dp, int dev, unsigned char *buf, if (sysex->skip) { sysex->skip = 0; sysex->len = 0; - return -EINVAL; /* skip */ + err = -EINVAL; /* skip */ + goto unlock_sysex; } /* copy the data to event record and send it */ ev->flags = SNDRV_SEQ_EVENT_LENGTH_VARIABLE; - if (snd_seq_oss_synth_addr(dp, dev, ev)) - return -EINVAL; + if (snd_seq_oss_synth_addr(dp, dev, ev)) { + err = -EINVAL; + goto unlock_sysex; + } ev->data.ext.len = sysex->len; ev->data.ext.ptr = sysex->buf; sysex->len = 0; + mutex_unlock(&sysex_mutex); return 0; } - return -EINVAL; /* skip */ +unlock_sysex: + mutex_unlock(&sysex_mutex); + return err; /* skip */ } /* -- 2.25.1