At Tue, 22 Mar 2011 14:31:08 -0400, Dan Rosenberg wrote:
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.
This patch fixes all these issues, as well as some cleanup to prevent checkpatch.pl from complaining.
Signed-off-by: Dan Rosenberg drosenberg@vsecurity.com Cc: stable@kernel.org
Well, the whole load_patch mechanism doesn't look working right with ofs != 0. The only caller of this callback is sound/oss/sequencer.c, and it assumes that the whole chunk is passed once without splitting. Thus the offset calculation in this code is obviously wrong, and passing offset itself doesn't make any sense.
A similar problem (uninitialized struct fields) is found in another load_patch callback in sound/oss/opl3.c.
That is, the best fix would be to rip off the offset argument from this callback.
thanks,
Takashi
sound/oss/midi_synth.c | 27 ++++++++++++++------------- 1 files changed, 14 insertions(+), 13 deletions(-)
diff --git a/sound/oss/midi_synth.c b/sound/oss/midi_synth.c index 3c09374..3500f80 100644 --- a/sound/oss/midi_synth.c +++ b/sound/oss/midi_synth.c @@ -491,16 +491,18 @@ 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;
- }
/* Offset too high */
if (offs > offsetof(struct sysex_info, len) || offs < 0)
return -EINVAL;count -= hdr_size;
/*
@@ -510,14 +512,13 @@ midi_synth_load_patch(int dev, int format, const char __user *addr,
if(copy_from_user(&((char *) &sysex)[offs], &(addr)[offs], hdr_size - offs)) 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++) {