From b769f49463711205d57286e64cf535ed4daf59e9 Mon Sep 17 00:00:00 2001 From: Dan Rosenberg Date: Wed, 23 Mar 2011 10:53:41 -0400 Subject: 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: Dan Rosenberg Signed-off-by: Takashi Iwai --- sound/oss/midi_synth.c | 30 +++++++++++++----------------- 1 file changed, 13 insertions(+), 17 deletions(-) (limited to 'sound/oss/midi_synth.c') diff --git a/sound/oss/midi_synth.c b/sound/oss/midi_synth.c index 3c09374ea5bf..2292c230d7e6 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++) { -- cgit v1.2.2