Prevent wrap-around in silk_resampler_down2_hp()

Would only happen on pathologically loud HF signals,
so this is just to make fuzzers happy.

Author: jmvalin

celt/arch.h

@@ -315,6 +315,8 @@ static OPUS_INLINE int celt_isnan(float x)
 #define PSHR32(a,shift) (a)
 #define VSHR32(a,shift) (a)
 
+#define SHR64(a,shift) (a)
+
 #define PSHR(a,shift)   (a)
 #define SHR(a,shift)    (a)
 #define SHL(a,shift)    (a)

celt/fixed_debug.h

@@ -241,6 +241,8 @@ static OPUS_INLINE int SHL32_(opus_int64 a, int shift, char *file, int line)
 #define PSHR32(a,shift) (celt_mips--,SHR32(ADD32((a),(((opus_val32)(1)<<((shift))>>1))),shift))
 #define VSHR32(a, shift) (((shift)>0) ? SHR32(a, shift) : SHL32(a, -(shift)))
 
+#define SHR64(a,shift) (celt_mips++,(a) >> (shift))
+
 #define ROUND16(x,a) (celt_mips--,EXTRACT16(PSHR32((x),(a))))
 #define SROUND16(x,a) (celt_mips--,EXTRACT16(SATURATE(PSHR32(x,a), 32767)));
 

celt/fixed_generic.h

@@ -114,6 +114,9 @@
 /** 32-bit arithmetic shift right where the argument can be negative */
 #define VSHR32(a, shift) (((shift)>0) ? SHR32(a, shift) : SHL32(a, -(shift)))
 
+/** Arithmetic shift-right of a 64-bit value */
+#define SHR64(a,shift) ((a) >> (shift))
+
 /** "RAW" macros, should not be used outside of this header file */
 #define SHR(a,shift) ((a) >> (shift))
 #define SHL(a,shift) SHL32(a,shift)

src/analysis.c

@@ -149,13 +149,15 @@ static opus_val32 silk_resampler_down2_hp(
         out32_hp  = ADD32( out32_hp, X );
         S[ 2 ] = ADD32( -in32, X );
 
-        hp_ener += out32_hp*(opus_val64)out32_hp;
+        /* len2 can be up to 480, so we shift by 8 to make it fit. */
+        hp_ener += SHR64(out32_hp*(opus_val64)out32_hp, 8);
         /* Add, convert back to int16 and store to output */
         out[ k ] = HALF32(out32);
     }
 #ifdef FIXED_POINT
-    /* len2 can be up to 480, so we shift by 8 more to make it fit. */
-    hp_ener = hp_ener >> (2*SIG_SHIFT + 8);
+    /* Fitting in 32 bits. */
+    hp_ener = hp_ener >> (2*SIG_SHIFT);
+    if (hp_ener > 2147483647) hp_ener = 2147483647;
 #endif
     return (opus_val32)hp_ener;
 }