sound/oss: remove offset from load_patch callbacks

PATCH Superseded Dan Rosenberg 2 participants 4 messages Mar 23, 2011 Sound

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Dan Rosenberg

author

2011-03-23 13:47 UTC #0 lore raw

PATCH v2 1/1 sound/oss: remove offset from load_patch callbacks

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 <[email protected]>

Cc [email protected]

---
 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(-)

sound/oss/dev_table.h +1 -1

index b7617be..0199a31 100644
@@ -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);

sound/oss/midi_synth.c +12 ~~-15~~

index 3c09374..8d3611c 100644
@@ -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++)
 	{

sound/oss/midi_synth.h +1 -1

index 6bc9d00..b64ddd6 100644
@@ -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);

sound/oss/opl3.c +2 -2

index 938c48c..a3bec38 100644
@@ -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)

sound/oss/sequencer.c +1 -1

index 5ea1098..2e842cb 100644
@@ -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;

Takashi Iwai

2011-03-23 13:59 UTC #1 lore raw

At Wed, 23 Mar 2011 09:47:22 -0400,

sound/oss/midi_synth.c midi_synth_load_patch(int dev, int format, const char __user *addr, · line 509

Quoted 8 lines · Dan Rosenberg

sound/oss/midi_synth.c +1 -1

@@ -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))

Please correct the comment in the above as well. With this change, the transfer is no longer partial.

Quoted 2 lines

sound/oss/opl3.c +0 -0

...

sound/oss/opl3.c static int opl3_load_patch(int dev, int format, const char __user *addr, · line 837

Quoted 6 lines

sound/oss/opl3.c +1 -1

@@ -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)))

Ditto.

sound/oss/sequencer.c int sequencer_write(int dev, struct file *file, const char __user *buf, int coun · line 244

Quoted 13 lines

sound/oss/opl3.c +0 -0

 		return -EFAULT;
 
 	if (ins.channel < 0 || ins.channel >= SBFM_MAXINSTR)

sound/oss/sequencer.c +1 -1

index 5ea1098..2e842cb 100644
@@ -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);

The address must be "buf + p + 4" instead of "buf", when you omit the offset argument.

thanks,

Takashi

Dan Rosenberg

author

2011-03-23 14:06 UTC #2 lore raw

Quoted 8 lines · Takashi Iwai

At Wed, 23 Mar 2011 09:47:22 -0400,
Quoted 6 lines · Dan Rosenberg
sound/oss/midi_synth.c +0 -0
@@ -508,16 +506,15 @@ midi_synth_load_patch(int dev, int format, const char __user *addr,
 	 * been transferred already.
 	 */
 

Quoted 5 lines

sound/oss/midi_synth.c midi_synth_load_patch(int dev, int format, const char __user *addr, · line 509
Quoted 2 lines
sound/oss/midi_synth.c +1 -1
-	if(copy_from_user(&((char *) &sysex)[offs], &(addr)[offs], hdr_size - offs))
+	if (copy_from_user(&sysex, addr, hdr_size))
Please correct the comment in the above as well. With this change, the transfer is no longer partial.

Will do.

Quoted 4 lines

Quoted 3 lines
sound/oss/opl3.c +0 -0
...

Quoted 8 lines

sound/oss/opl3.c static int opl3_load_patch(int dev, int format, const char __user *addr, · line 837

Quoted 6 lines

sound/oss/opl3.c +1 -1

@@ -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)))

Ditto.

Likewise.

Quoted 11 lines

sound/oss/opl3.c +0 -0

 		return -EFAULT;
 
 	if (ins.channel < 0 || ins.channel >= SBFM_MAXINSTR)

sound/oss/sequencer.c +0 -0

index 5ea1098..2e842cb 100644
@@ -241,7 +241,7 @@ int sequencer_write(int dev, struct file *file, const char __user *buf, int coun
 				return -ENXIO;

Quoted 7 lines

sound/oss/sequencer.c int sequencer_write(int dev, struct file *file, const char __user *buf, int coun · line 244
Quoted 3 lines
sound/oss/sequencer.c +1 -1
 			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);
The address must be "buf + p + 4" instead of "buf", when you omit the offset argument.

Are you sure? Previously, the copy of the header was from (buf + p + 4) to (dst + p + 4) with length (hdr_size - (p + 4)), and now the copy is from buf to dst with length hdr_size. If I do as you suggest, then the copy will be from (buf + p + 4) to dst for the header.

-Dan

Quoted 4 lines

thanks,
Takashi

Takashi Iwai

2011-03-23 14:47 UTC #3 lore raw

At Wed, 23 Mar 2011 10:06:22 -0400,

Quoted 52 lines · Dan Rosenberg

Quoted 8 lines · Takashi Iwai
At Wed, 23 Mar 2011 09:47:22 -0400,
Quoted 6 lines · Dan Rosenberg
sound/oss/midi_synth.c +0 -0
@@ -508,16 +506,15 @@ midi_synth_load_patch(int dev, int format, const char __user *addr,
 	 * been transferred already.
 	 */
 
Quoted 5 lines
sound/oss/midi_synth.c midi_synth_load_patch(int dev, int format, const char __user *addr, · line 509
Quoted 2 lines
sound/oss/midi_synth.c +1 -1
-	if(copy_from_user(&((char *) &sysex)[offs], &(addr)[offs], hdr_size - offs))
+	if (copy_from_user(&sysex, addr, hdr_size))
Please correct the comment in the above as well. With this change, the transfer is no longer partial.
Will do.
Quoted 4 lines
Quoted 3 lines
sound/oss/opl3.c +0 -0
...
Quoted 8 lines
sound/oss/opl3.c static int opl3_load_patch(int dev, int format, const char __user *addr, · line 837
Quoted 6 lines
sound/oss/opl3.c +1 -1
@@ -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)))
Ditto.
Likewise.
Quoted 11 lines
Quoted 11 lines
sound/oss/opl3.c +0 -0
 		return -EFAULT;
 
 	if (ins.channel < 0 || ins.channel >= SBFM_MAXINSTR)
sound/oss/sequencer.c +0 -0
index 5ea1098..2e842cb 100644
@@ -241,7 +241,7 @@ int sequencer_write(int dev, struct file *file, const char __user *buf, int coun
 				return -ENXIO;
 
Quoted 7 lines
sound/oss/sequencer.c int sequencer_write(int dev, struct file *file, const char __user *buf, int coun · line 244
Quoted 3 lines
sound/oss/sequencer.c +1 -1
 			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);
The address must be "buf + p + 4" instead of "buf", when you omit the offset argument.

Quoted 4 lines

Are you sure? Previously, the copy of the header was from (buf + p + 4) to (dst + p + 4) with length (hdr_size - (p + 4)), and now the copy is from buf to dst with length hdr_size. If I do as you suggest, then the copy will be from (buf + p + 4) to dst for the header.

Hm, looking back to the original code, I found that I almost forgot the trickiness of patch-loading in OSS. Actually, it should be like:

	err = synth_devs[dev]->load_patch(dev, fmt, buf + p, c, 0);

Here, "buf + p" points to the 4-byte event packet that is being processed. And, these 4 bytes are also shared with the first 4 bytes of struct sysex_info or struct sbi_instrument. That is, sysex_info.key == fmt and sysex_info.device_no == dev.

The problem in the original code is that it tries to avoid extra copying of these 4 bytes, but failed to handle correctly, by misinterpreting offs parameter.

thanks,

Takashi