[PATCH 3.16 213/366] ALSA: seq: oss: Hardening for potential Spectre v1

3.16.60-rc1 review patch. If anyone has any objections, please let me know.

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From: Takashi Iwai tiwai@suse.de

commit 8d218dd8116695ecda7164f97631c069938aa22e upstream.

As Smatch recently suggested, a few places in OSS sequencer codes may expand the array directly from the user-space value with speculation, namely there are a significant amount of references to either info->ch[] or dp->synths[] array:

sound/core/seq/oss/seq_oss_event.c:315 note_on_event() warn: potential spectre issue 'info->ch' (local cap) sound/core/seq/oss/seq_oss_event.c:362 note_off_event() warn: potential spectre issue 'info->ch' (local cap) sound/core/seq/oss/seq_oss_synth.c:470 snd_seq_oss_synth_load_patch() warn: potential spectre issue 'dp->synths' (local cap) sound/core/seq/oss/seq_oss_event.c:293 note_on_event() warn: potential spectre issue 'dp->synths' sound/core/seq/oss/seq_oss_event.c:353 note_off_event() warn: potential spectre issue 'dp->synths' sound/core/seq/oss/seq_oss_synth.c:506 snd_seq_oss_synth_sysex() warn: potential spectre issue 'dp->synths' sound/core/seq/oss/seq_oss_synth.c:580 snd_seq_oss_synth_ioctl() warn: potential spectre issue 'dp->synths'

Although all these seem doing only the first load without further reference, we may want to stay in a safer side, so hardening with array_index_nospec() would still make sense.

We may put array_index_nospec() at each place, but here we take a different approach:

- For dp->synths[], change the helpers to retrieve seq_oss_synthinfo pointer directly instead of the array expansion at each place

- For info->ch[], harden in a normal way, as there are only a couple of places

As a result, the existing helper, snd_seq_oss_synth_is_valid() is replaced with snd_seq_oss_synth_info(). Also, we cover MIDI device where a similar array expansion is done, too, although it wasn't reported by Smatch.

BugLink: https://marc.info/?l=linux-kernel&m=152411496503418&w=2 Reported-by: Dan Carpenter dan.carpenter@oracle.com Signed-off-by: Takashi Iwai tiwai@suse.de Signed-off-by: Ben Hutchings ben@decadent.org.uk --- sound/core/seq/oss/seq_oss_event.c | 15 +++--- sound/core/seq/oss/seq_oss_midi.c | 2 + sound/core/seq/oss/seq_oss_synth.c | 75 +++++++++++++++++------------- sound/core/seq/oss/seq_oss_synth.h | 3 +- 4 files changed, 55 insertions(+), 40 deletions(-)

--- a/sound/core/seq/oss/seq_oss_event.c +++ b/sound/core/seq/oss/seq_oss_event.c @@ -26,6 +26,7 @@ #include <sound/seq_oss_legacy.h> #include "seq_oss_readq.h" #include "seq_oss_writeq.h" +#include <linux/nospec.h>

/* @@ -287,10 +288,10 @@ note_on_event(struct seq_oss_devinfo *dp { struct seq_oss_synthinfo *info;

- if (!snd_seq_oss_synth_is_valid(dp, dev)) + info = snd_seq_oss_synth_info(dp, dev); + if (!info) return -ENXIO;

- info = &dp->synths[dev]; switch (info->arg.event_passing) { case SNDRV_SEQ_OSS_PROCESS_EVENTS: if (! info->ch || ch < 0 || ch >= info->nr_voices) { @@ -298,6 +299,7 @@ note_on_event(struct seq_oss_devinfo *dp return set_note_event(dp, dev, SNDRV_SEQ_EVENT_NOTEON, ch, note, vel, ev); }

+ ch = array_index_nospec(ch, info->nr_voices); if (note == 255 && info->ch[ch].note >= 0) { /* volume control */ int type; @@ -347,10 +349,10 @@ note_off_event(struct seq_oss_devinfo *d { struct seq_oss_synthinfo *info;

- if (!snd_seq_oss_synth_is_valid(dp, dev)) + info = snd_seq_oss_synth_info(dp, dev); + if (!info) return -ENXIO;

- info = &dp->synths[dev]; switch (info->arg.event_passing) { case SNDRV_SEQ_OSS_PROCESS_EVENTS: if (! info->ch || ch < 0 || ch >= info->nr_voices) { @@ -358,6 +360,7 @@ note_off_event(struct seq_oss_devinfo *d return set_note_event(dp, dev, SNDRV_SEQ_EVENT_NOTEON, ch, note, vel, ev); }

+ ch = array_index_nospec(ch, info->nr_voices); if (info->ch[ch].note >= 0) { note = info->ch[ch].note; info->ch[ch].vel = 0; @@ -381,7 +384,7 @@ note_off_event(struct seq_oss_devinfo *d static int set_note_event(struct seq_oss_devinfo *dp, int dev, int type, int ch, int note, int vel, struct snd_seq_event *ev) { - if (! snd_seq_oss_synth_is_valid(dp, dev)) + if (!snd_seq_oss_synth_info(dp, dev)) return -ENXIO; ev->type = type; @@ -399,7 +402,7 @@ set_note_event(struct seq_oss_devinfo *d static int set_control_event(struct seq_oss_devinfo *dp, int dev, int type, int ch, int param, int val, struct snd_seq_event *ev) { - if (! snd_seq_oss_synth_is_valid(dp, dev)) + if (!snd_seq_oss_synth_info(dp, dev)) return -ENXIO; ev->type = type; --- a/sound/core/seq/oss/seq_oss_midi.c +++ b/sound/core/seq/oss/seq_oss_midi.c @@ -29,6 +29,7 @@ #include "../seq_lock.h" #include <linux/init.h> #include <linux/slab.h> +#include <linux/nospec.h>

/* @@ -318,6 +319,7 @@ get_mididev(struct seq_oss_devinfo *dp, { if (dev < 0 || dev >= dp->max_mididev) return NULL; + dev = array_index_nospec(dev, dp->max_mididev); return get_mdev(dev); }

--- a/sound/core/seq/oss/seq_oss_synth.c +++ b/sound/core/seq/oss/seq_oss_synth.c @@ -26,6 +26,7 @@ #include <linux/init.h> #include <linux/module.h> #include <linux/slab.h> +#include <linux/nospec.h>

/* * constants @@ -339,17 +340,13 @@ snd_seq_oss_synth_cleanup(struct seq_oss dp->max_synthdev = 0; }

-/* - * check if the specified device is MIDI mapped device - */ -static int -is_midi_dev(struct seq_oss_devinfo *dp, int dev) +static struct seq_oss_synthinfo * +get_synthinfo_nospec(struct seq_oss_devinfo *dp, int dev) { if (dev < 0 || dev >= dp->max_synthdev) - return 0; - if (dp->synths[dev].is_midi) - return 1; - return 0; + return NULL; + dev = array_index_nospec(dev, SNDRV_SEQ_OSS_MAX_SYNTH_DEVS); + return &dp->synths[dev]; }

/* @@ -359,11 +356,13 @@ static struct seq_oss_synth * get_synthdev(struct seq_oss_devinfo *dp, int dev) { struct seq_oss_synth *rec; - if (dev < 0 || dev >= dp->max_synthdev) + struct seq_oss_synthinfo *info = get_synthinfo_nospec(dp, dev); + + if (!info) return NULL; - if (! dp->synths[dev].opened) + if (!info->opened) return NULL; - if (dp->synths[dev].is_midi) { + if (info->is_midi) { rec = &midi_synth_dev; snd_use_lock_use(&rec->use_lock); } else { @@ -406,10 +405,8 @@ snd_seq_oss_synth_reset(struct seq_oss_d struct seq_oss_synth *rec; struct seq_oss_synthinfo *info;

- if (snd_BUG_ON(dev < 0 || dev >= dp->max_synthdev)) - return; - info = &dp->synths[dev]; - if (! info->opened) + info = get_synthinfo_nospec(dp, dev); + if (!info || !info->opened) return; if (info->sysex) info->sysex->len = 0; /* reset sysex */ @@ -458,12 +455,14 @@ snd_seq_oss_synth_load_patch(struct seq_ const char __user *buf, int p, int c) { struct seq_oss_synth *rec; + struct seq_oss_synthinfo *info; int rc;

- if (dev < 0 || dev >= dp->max_synthdev) + info = get_synthinfo_nospec(dp, dev); + if (!info) return -ENXIO;

- if (is_midi_dev(dp, dev)) + if (info->is_midi) return 0; if ((rec = get_synthdev(dp, dev)) == NULL) return -ENXIO; @@ -471,24 +470,25 @@ snd_seq_oss_synth_load_patch(struct seq_ if (rec->oper.load_patch == NULL) rc = -ENXIO; else - rc = rec->oper.load_patch(&dp->synths[dev].arg, fmt, buf, p, c); + rc = rec->oper.load_patch(&info->arg, fmt, buf, p, c); snd_use_lock_free(&rec->use_lock); return rc; }

/* - * check if the device is valid synth device + * check if the device is valid synth device and return the synth info */ -int -snd_seq_oss_synth_is_valid(struct seq_oss_devinfo *dp, int dev) +struct seq_oss_synthinfo * +snd_seq_oss_synth_info(struct seq_oss_devinfo *dp, int dev) { struct seq_oss_synth *rec; + rec = get_synthdev(dp, dev); if (rec) { snd_use_lock_free(&rec->use_lock); - return 1; + return get_synthinfo_nospec(dp, dev); } - return 0; + return NULL; }

@@ -503,16 +503,18 @@ snd_seq_oss_synth_sysex(struct seq_oss_d int i, send; unsigned char *dest; struct seq_oss_synth_sysex *sysex; + struct seq_oss_synthinfo *info;

- if (! snd_seq_oss_synth_is_valid(dp, dev)) + info = snd_seq_oss_synth_info(dp, dev); + if (!info) return -ENXIO;

- sysex = dp->synths[dev].sysex; + sysex = info->sysex; if (sysex == NULL) { sysex = kzalloc(sizeof(*sysex), GFP_KERNEL); if (sysex == NULL) return -ENOMEM; - dp->synths[dev].sysex = sysex; + info->sysex = sysex; }

send = 0; @@ -557,10 +559,12 @@ snd_seq_oss_synth_sysex(struct seq_oss_d int snd_seq_oss_synth_addr(struct seq_oss_devinfo *dp, int dev, struct snd_seq_event *ev) { - if (! snd_seq_oss_synth_is_valid(dp, dev)) + struct seq_oss_synthinfo *info = snd_seq_oss_synth_info(dp, dev); + + if (!info) return -EINVAL; - snd_seq_oss_fill_addr(dp, ev, dp->synths[dev].arg.addr.client, - dp->synths[dev].arg.addr.port); + snd_seq_oss_fill_addr(dp, ev, info->arg.addr.client, + info->arg.addr.port); return 0; }

@@ -572,16 +576,18 @@ int snd_seq_oss_synth_ioctl(struct seq_oss_devinfo *dp, int dev, unsigned int cmd, unsigned long addr) { struct seq_oss_synth *rec; + struct seq_oss_synthinfo *info; int rc;

- if (is_midi_dev(dp, dev)) + info = get_synthinfo_nospec(dp, dev); + if (!info || info->is_midi) return -ENXIO; if ((rec = get_synthdev(dp, dev)) == NULL) return -ENXIO; if (rec->oper.ioctl == NULL) rc = -ENXIO; else - rc = rec->oper.ioctl(&dp->synths[dev].arg, cmd, addr); + rc = rec->oper.ioctl(&info->arg, cmd, addr); snd_use_lock_free(&rec->use_lock); return rc; } @@ -593,7 +599,10 @@ snd_seq_oss_synth_ioctl(struct seq_oss_d int snd_seq_oss_synth_raw_event(struct seq_oss_devinfo *dp, int dev, unsigned char *data, struct snd_seq_event *ev) { - if (! snd_seq_oss_synth_is_valid(dp, dev) || is_midi_dev(dp, dev)) + struct seq_oss_synthinfo *info; + + info = snd_seq_oss_synth_info(dp, dev); + if (!info || info->is_midi) return -ENXIO; ev->type = SNDRV_SEQ_EVENT_OSS; memcpy(ev->data.raw8.d, data, 8); --- a/sound/core/seq/oss/seq_oss_synth.h +++ b/sound/core/seq/oss/seq_oss_synth.h @@ -37,7 +37,8 @@ void snd_seq_oss_synth_cleanup(struct se void snd_seq_oss_synth_reset(struct seq_oss_devinfo *dp, int dev); int snd_seq_oss_synth_load_patch(struct seq_oss_devinfo *dp, int dev, int fmt, const char __user *buf, int p, int c); -int snd_seq_oss_synth_is_valid(struct seq_oss_devinfo *dp, int dev); +struct seq_oss_synthinfo *snd_seq_oss_synth_info(struct seq_oss_devinfo *dp, + int dev); int snd_seq_oss_synth_sysex(struct seq_oss_devinfo *dp, int dev, unsigned char *buf, struct snd_seq_event *ev); int snd_seq_oss_synth_addr(struct seq_oss_devinfo *dp, int dev, struct snd_seq_event *ev);