At Wed, 23 Mar 2011 10:53:41 -0400, Dan Rosenberg wrote:

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.

v3 adjusts comments and hopefully gets copy offsets right.

Signed-off-by: Dan Rosenberg drosenberg@vsecurity.com

Applied now. Thanks.

Takashi

---

sound/oss/dev_table.h | 2 +- sound/oss/midi_synth.c | 30 +++++++++++++----------------- sound/oss/midi_synth.h | 2 +- sound/oss/opl3.c | 8 ++------ sound/oss/sequencer.c | 2 +- 5 files changed, 18 insertions(+), 26 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..2292c23 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;

@@ -491,33 +491,29 @@ 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;

  /*

• * Copy the header from user space but ignore the first bytes which have
  

• * been transferred already.
  

• * Copy the header from user space
  

  */

• 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..cbf9574 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;

@@ -830,11 +830,7 @@ static int opl3_load_patch(int dev, int format, const char __user *addr, return -EINVAL; }

• /*

• * 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..30bcfe4 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 + p, c, 0);
  if (err < 0)
  	return err;