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sound/oss: remove offset from load_patch callbacks

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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>
Signed-off-by: Takashi Iwai <tiwai@suse.de>
This commit is contained in:
Dan Rosenberg
2011-03-23 10:53:41 -04:00
committed by Takashi Iwai
parent ce24f58a11
commit b769f49463
5 changed files with 18 additions and 26 deletions
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30
sound/oss/midi_synth.c
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@ -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++)
{