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Message-ID: <s5h62r9wl2b.wl%tiwai@suse.de>
Date: Wed, 23 Mar 2011 23:04:12 +0100
From: Takashi Iwai <tiwai@...e.de>
To: Dan Rosenberg <drosenberg@...curity.com>
Cc: perex@...ex.cz, alsa-devel@...a-project.org, security@...nel.org,
linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3] sound/oss: remove offset from load_patch callbacks
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@...curity.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;
>
>
>
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