Was: [PATCH] sound/oss/midi_synth: prevent underflow, use of uninitialized value, and signedness issue

The offset passed to midi_synth_load_patch() can be essentially arbitrary. If it's greater than the header length, this will result in a copy_from_user(dst, src, negative_val). While this will just return -EFAULT on x86, on other architectures this may cause memory corruption. Additionally, the length field of the sysex_info structure may not be initialized prior to its use. Finally, a signed comparison may result in an unintentionally large loop.

On suggestion by Takashi Iwai, version two removes the offset argument from the load_patch callbacks entirely, which also resolves similar issues in opl3. Compile tested only.

Signed-off-by: Dan Rosenberg drosenberg@vsecurity.com Cc: stable@kernel.org --- sound/oss/dev_table.h | 2 +- sound/oss/midi_synth.c | 27 ++++++++++++--------------- sound/oss/midi_synth.h | 2 +- sound/oss/opl3.c | 4 ++-- sound/oss/sequencer.c | 2 +- 5 files changed, 17 insertions(+), 20 deletions(-)

diff --git a/sound/oss/dev_table.h b/sound/oss/dev_table.h index b7617be..0199a31 100644 --- a/sound/oss/dev_table.h +++ b/sound/oss/dev_table.h @@ -271,7 +271,7 @@ struct synth_operations void (*reset) (int dev); void (*hw_control) (int dev, unsigned char *event); int (*load_patch) (int dev, int format, const char __user *addr, - int offs, int count, int pmgr_flag); + int count, int pmgr_flag); void (*aftertouch) (int dev, int voice, int pressure); void (*controller) (int dev, int voice, int ctrl_num, int value); void (*panning) (int dev, int voice, int value); diff --git a/sound/oss/midi_synth.c b/sound/oss/midi_synth.c index 3c09374..8d3611c 100644 --- a/sound/oss/midi_synth.c +++ b/sound/oss/midi_synth.c @@ -476,7 +476,7 @@ EXPORT_SYMBOL(midi_synth_hw_control);

int midi_synth_load_patch(int dev, int format, const char __user *addr, - int offs, int count, int pmgr_flag) + int count, int pmgr_flag) { int orig_dev = synth_devs[dev]->midi_dev;

@@ -491,16 +491,14 @@ midi_synth_load_patch(int dev, int format, const char __user *addr, if (!prefix_cmd(orig_dev, 0xf0)) return 0;

+ /* Invalid patch format */ if (format != SYSEX_PATCH) - { -/* printk("MIDI Error: Invalid patch format (key) 0x%x\n", format);*/ return -EINVAL; - } + + /* Patch header too short */ if (count < hdr_size) - { -/* printk("MIDI Error: Patch header too short\n");*/ return -EINVAL; - } + count -= hdr_size;

/* @@ -508,16 +506,15 @@ midi_synth_load_patch(int dev, int format, const char __user *addr, * been transferred already. */

- if(copy_from_user(&((char *) &sysex)[offs], &(addr)[offs], hdr_size - offs)) + if (copy_from_user(&sysex, addr, hdr_size)) return -EFAULT; - - if (count < sysex.len) - { -/* printk(KERN_WARNING "MIDI Warning: Sysex record too short (%d<%d)\n", count, (int) sysex.len);*/ + + /* Sysex record too short */ + if ((unsigned)count < (unsigned)sysex.len) sysex.len = count; - } - left = sysex.len; - src_offs = 0; + + left = sysex.len; + src_offs = 0;

for (i = 0; i < left && !signal_pending(current); i++) { diff --git a/sound/oss/midi_synth.h b/sound/oss/midi_synth.h index 6bc9d00..b64ddd6 100644 --- a/sound/oss/midi_synth.h +++ b/sound/oss/midi_synth.h @@ -8,7 +8,7 @@ int midi_synth_open (int dev, int mode); void midi_synth_close (int dev); void midi_synth_hw_control (int dev, unsigned char *event); int midi_synth_load_patch (int dev, int format, const char __user * addr, - int offs, int count, int pmgr_flag); + int count, int pmgr_flag); void midi_synth_panning (int dev, int channel, int pressure); void midi_synth_aftertouch (int dev, int channel, int pressure); void midi_synth_controller (int dev, int channel, int ctrl_num, int value); diff --git a/sound/oss/opl3.c b/sound/oss/opl3.c index 938c48c..a3bec38 100644 --- a/sound/oss/opl3.c +++ b/sound/oss/opl3.c @@ -820,7 +820,7 @@ static void opl3_hw_control(int dev, unsigned char *event) }

static int opl3_load_patch(int dev, int format, const char __user *addr, - int offs, int count, int pmgr_flag) + int count, int pmgr_flag) { struct sbi_instrument ins;

@@ -834,7 +834,7 @@ static int opl3_load_patch(int dev, int format, const char __user *addr, * What the fuck is going on here? We leave junk in the beginning * of ins and then check the field pretty close to that beginning? */ - if(copy_from_user(&((char *) &ins)[offs], addr + offs, sizeof(ins) - offs)) + if (copy_from_user(&ins, addr, sizeof(ins))) return -EFAULT;

if (ins.channel < 0 || ins.channel >= SBFM_MAXINSTR) diff --git a/sound/oss/sequencer.c b/sound/oss/sequencer.c index 5ea1098..2e842cb 100644 --- a/sound/oss/sequencer.c +++ b/sound/oss/sequencer.c @@ -241,7 +241,7 @@ int sequencer_write(int dev, struct file *file, const char __user *buf, int coun return -ENXIO;

fmt = (*(short *) &event_rec[0]) & 0xffff; - err = synth_devs[dev]->load_patch(dev, fmt, buf, p + 4, c, 0); + err = synth_devs[dev]->load_patch(dev, fmt, buf, c, 0); if (err < 0) return err;