Commit b769f494 authored by Dan Rosenberg's avatar Dan Rosenberg Committed by Takashi Iwai
Browse files

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.

v3 adjusts comments and hopefully gets copy offsets right.

Signed-off-by: default avatarDan Rosenberg <drosenberg@vsecurity.com>
Signed-off-by: default avatarTakashi Iwai <tiwai@suse.de>
parent ce24f58a

sound/oss/dev_table.h

+1 −1
Original line number Diff line number Diff line
@@ -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

+13 −17
Original line number Diff line number Diff line
@@ -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;
@@ -491,31 +491,27 @@ 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;

sound/oss/midi_synth.h

+1 −1
Original line number Diff line number Diff line
@@ -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 −6
Original line number Diff line number Diff line
@@ -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)

sound/oss/sequencer.c

+1 −1
Original line number Diff line number Diff line
@@ -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;

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