1 files changed, 68 insertions, 20 deletions

diff --git a/lib/reed_solomon/decode_rs.c b/lib/reed_solomon/decode_rs.c
index b7264a712d46..805de84ae83d 100644
--- a/lib/reed_solomon/decode_rs.c
+++ b/lib/reed_solomon/decode_rs.c
@@ -22,6 +22,7 @@
 	uint16_t *index_of = rs->index_of;
 	uint16_t u, q, tmp, num1, num2, den, discr_r, syn_error;
 	int count = 0;
+	int num_corrected;
 	uint16_t msk = (uint16_t) rs->nn;
 
 	/*
@@ -184,6 +185,15 @@
 		if (lambda[i] != nn)
 			deg_lambda = i;
 	}
+
+	if (deg_lambda == 0) {
+		/*
+		 * deg(lambda) is zero even though the syndrome is non-zero
+		 * => uncorrectable error detected
+		 */
+		return -EBADMSG;
+	}
+
 	/* Find roots of error+erasure locator polynomial by Chien search */
 	memcpy(&reg[1], &lambda[1], nroots * sizeof(reg[0]));
 	count = 0;		/* Number of roots of lambda(x) */
@@ -197,6 +207,12 @@
 		}
 		if (q != 0)
 			continue;	/* Not a root */
+
+		if (k < pad) {
+			/* Impossible error location. Uncorrectable error. */
+			return -EBADMSG;
+		}
+
 		/* store root (index-form) and error location number */
 		root[count] = i;
 		loc[count] = k;
@@ -231,7 +247,9 @@
 	/*
 	 * Compute error values in poly-form. num1 = omega(inv(X(l))), num2 =
 	 * inv(X(l))**(fcr-1) and den = lambda_pr(inv(X(l))) all in poly-form
+	 * Note: we reuse the buffer for b to store the correction pattern
 	 */
+	num_corrected = 0;
 	for (j = count - 1; j >= 0; j--) {
 		num1 = 0;
 		for (i = deg_omega; i >= 0; i--) {
@@ -239,6 +257,13 @@
 				num1 ^= alpha_to[rs_modnn(rs, omega[i] +
 							i * root[j])];
 		}
+
+		if (num1 == 0) {
+			/* Nothing to correct at this position */
+			b[j] = 0;
+			continue;
+		}
+
 		num2 = alpha_to[rs_modnn(rs, root[j] * (fcr - 1) + nn)];
 		den = 0;
 
@@ -250,29 +275,52 @@
 						       i * root[j])];
 			}
 		}
-		/* Apply error to data */
-		if (num1 != 0 && loc[j] >= pad) {
-			uint16_t cor = alpha_to[rs_modnn(rs,index_of[num1] +
-						       index_of[num2] +
-						       nn - index_of[den])];
-			/* Store the error correction pattern, if a
-			 * correction buffer is available */
-			if (corr) {
-				corr[j] = cor;
-			} else {
-				/* If a data buffer is given and the
-				 * error is inside the message,
-				 * correct it */
-				if (data && (loc[j] < (nn - nroots)))
-					data[loc[j] - pad] ^= cor;
-			}
+
+		b[j] = alpha_to[rs_modnn(rs, index_of[num1] +
+					       index_of[num2] +
+					       nn - index_of[den])];
+		num_corrected++;
+	}
+
+	/*
+	 * We compute the syndrome of the 'error' and check that it matches
+	 * the syndrome of the received word
+	 */
+	for (i = 0; i < nroots; i++) {
+		tmp = 0;
+		for (j = 0; j < count; j++) {
+			if (b[j] == 0)
+				continue;
+
+			k = (fcr + i) * prim * (nn-loc[j]-1);
+			tmp ^= alpha_to[rs_modnn(rs, index_of[b[j]] + k)];
 		}
+
+		if (tmp != alpha_to[s[i]])
+			return -EBADMSG;
 	}
 
-	if (eras_pos != NULL) {
-		for (i = 0; i < count; i++)
-			eras_pos[i] = loc[i] - pad;
+	/*
+	 * Store the error correction pattern, if a
+	 * correction buffer is available
+	 */
+	if (corr && eras_pos) {
+		j = 0;
+		for (i = 0; i < count; i++) {
+			if (b[i]) {
+				corr[j] = b[i];
+				eras_pos[j++] = loc[i] - pad;
+			}
+		}
+	} else if (data && par) {
+		/* Apply error to data and parity */
+		for (i = 0; i < count; i++) {
+			if (loc[i] < (nn - nroots))
+				data[loc[i] - pad] ^= b[i];
+			else
+				par[loc[i] - pad - len] ^= b[i];
+		}
 	}
-	return count;
 
+	return  num_corrected;
 }