[PATCH] sb_mixer bounds checking

From: Muli Ben-Yehuda <mulix@mulix.org>

This patch add proper bounds checking to the sb_mixer.c code, found by the
stanford checker[0].  It fixes bugzilla bugs 252[1], 253[2] and 254[3]. 
Patch is against 2.6.5-rc2.  It was tested by Rene Herman on SN AWE64 gold
and sound still works.  The issue was previously discussed on lkml[4], but
apparently no fix was applied.

The patch is a bit more intrusive than I would've liked, but I don't think
it can be helped without really intrusive changes.  sb_devc has a pointer
to an array (iomap) that is set at run time to point to arrays of variable
sizes.  The patch adds an 'iomap_sz' member to sb_devc that is set to the
length of the array, and does bounds checking in sb_common_mixer_set() and
smw_mixer_set() agains that.

sound/oss/sb.h

@@ -110,6 +110,7 @@ typedef struct sb_devc {
 	/* Mixer fields */
 	   int *levels;
 	   mixer_tab *iomap;
+	   size_t iomap_sz; /* number or records in the iomap table */
 	   int mixer_caps, recmask, outmask, supported_devices;
 	   int supported_rec_devices, supported_out_devices;
 	   int my_mixerdev;

sound/oss/sb_ess.c

@@ -1638,8 +1638,10 @@ printk (KERN_INFO "FKS: ess_mixer_init dup = %d\n", devc->duplex);
 #endif
 		if (devc->duplex) {
 			devc->iomap				= &es1887_mix;
+			devc->iomap_sz                          = ARRAY_SIZE(es1887_mix);
 		} else {
 			devc->iomap				= &es_rec_mix;
+			devc->iomap_sz                          = ARRAY_SIZE(es_rec_mix);
 		}
 		break;
 	default:
@@ -1647,6 +1649,7 @@ printk (KERN_INFO "FKS: ess_mixer_init dup = %d\n", devc->duplex);
 			devc->supported_devices		= ES688_MIXER_DEVICES;
 			devc->supported_rec_devices	= ES688_RECORDING_DEVICES;
 			devc->iomap					= &es688_mix;
+			devc->iomap_sz                                  = ARRAY_SIZE(es688_mix);
 		} else {
 			/*
 			 * es1688 has 4 bits master vol.
@@ -1656,8 +1659,10 @@ printk (KERN_INFO "FKS: ess_mixer_init dup = %d\n", devc->duplex);
 			devc->supported_rec_devices	= ES1688_RECORDING_DEVICES;
 			if (devc->submodel < 0x10) {
 				devc->iomap				= &es1688_mix;
+				devc->iomap_sz                          = ARRAY_SIZE(es688_mix);
 			} else {
 				devc->iomap				= &es1688later_mix;
+				devc->iomap_sz                          = ARRAY_SIZE(es1688later_mix);
 			}
 		}
 	}

sound/oss/sb_mixer.c

@@ -278,6 +278,9 @@ int sb_common_mixer_set(sb_devc * devc, int dev, int left, int right)
 	if (regoffs == 0)
 		return -EINVAL;
 
+	if ((dev < 0) || (dev >= devc->iomap_sz))
+	    return -EINVAL;
+
 	val = sb_getmixer(devc, regoffs);
 	change_bits(devc, &val, dev, LEFT_CHN, left);
 
@@ -333,6 +336,9 @@ static int smw_mixer_set(sb_devc * devc, int dev, int left, int right)
 			break;
 
 		default:
+			/* bounds check */
+			if (dev < 0 || dev >= ARRAY_SIZE(smw_mix_regs))
+				return -EINVAL;
 			reg = smw_mix_regs[dev];
 			if (reg == 0)
 				return -EINVAL;
@@ -355,7 +361,7 @@ static int sb_mixer_set(sb_devc * devc, int dev, int value)
 	if (right > 100)
 		right = 100;
 
-	if (dev > 31)
+	if ((dev < 0) || (dev > 31))
 		return -EINVAL;
 
 	if (!(devc->supported_devices & (1 << dev)))	/*
@@ -684,6 +690,7 @@ int sb_mixer_init(sb_devc * devc, struct module *owner)
 			devc->supported_devices = SBPRO_MIXER_DEVICES;
 			devc->supported_rec_devices = SBPRO_RECORDING_DEVICES;
 			devc->iomap = &sbpro_mix;
+			devc->iomap_sz = ARRAY_SIZE(sbpro_mix);
 			break;
 
 		case MDL_ESS:
@@ -695,6 +702,7 @@ int sb_mixer_init(sb_devc * devc, struct module *owner)
 			devc->supported_devices = 0;
 			devc->supported_rec_devices = 0;
 			devc->iomap = &sbpro_mix;
+			devc->iomap_sz = ARRAY_SIZE(sbpro_mix);
 			smw_mixer_init(devc);
 			break;
 
@@ -706,11 +714,13 @@ int sb_mixer_init(sb_devc * devc, struct module *owner)
 			{
 				devc->supported_devices = SB16_MIXER_DEVICES;
 				devc->iomap = &sb16_mix;
+				devc->iomap_sz = ARRAY_SIZE(sb16_mix);
 			}
 			else
 			{
 				devc->supported_devices = ALS007_MIXER_DEVICES;
 				devc->iomap = &als007_mix;
+				devc->iomap_sz = ARRAY_SIZE(als007_mix);
 			}
 			break;