pcx: Do not overread source buffer in pcx_rle_decode

Reported-by: Mateusz "j00ru" Jurczyk and Gynvael Coldwind
CC: libav-stable@libav.org

libavcodec/pcx.c

@@ -31,7 +31,9 @@
 /**
  * @return advanced src pointer
  */
-static const uint8_t *pcx_rle_decode(const uint8_t *src, uint8_t *dst,
+static const uint8_t *pcx_rle_decode(const uint8_t *src,
+                                     const uint8_t *end,
+                                     uint8_t *dst,
                                      unsigned int bytes_per_scanline,
                                      int compressed)
 {
@@ -39,10 +41,10 @@ static const uint8_t *pcx_rle_decode(const uint8_t *src, uint8_t *dst,
     unsigned char run, value;
 
     if (compressed) {
-        while (i < bytes_per_scanline) {
+        while (i < bytes_per_scanline && src < end) {
             run   = 1;
             value = *src++;
-            if (value >= 0xc0) {
+            if (value >= 0xc0 && src < end) {
                 run   = value & 0x3f;
                 value = *src++;
             }
@@ -78,6 +80,7 @@ static int pcx_decode_frame(AVCodecContext *avctx, void *data, int *got_frame,
     unsigned int w, h, bits_per_pixel, bytes_per_line, nplanes, stride, y, x,
                  bytes_per_scanline;
     uint8_t *ptr;
+    const uint8_t *buf_end = buf + buf_size;
     uint8_t const *bufstart = buf;
     uint8_t *scanline;
     int ret = -1;
@@ -106,7 +109,8 @@ static int pcx_decode_frame(AVCodecContext *avctx, void *data, int *got_frame,
     nplanes            = buf[65];
     bytes_per_scanline = nplanes * bytes_per_line;
 
-    if (bytes_per_scanline < w * bits_per_pixel * nplanes / 8) {
+    if (bytes_per_scanline < w * bits_per_pixel * nplanes / 8 ||
+        (!compressed && bytes_per_scanline > buf_size / h)) {
         av_log(avctx, AV_LOG_ERROR, "PCX data is corrupted\n");
         return AVERROR_INVALIDDATA;
     }
@@ -151,7 +155,8 @@ static int pcx_decode_frame(AVCodecContext *avctx, void *data, int *got_frame,
 
     if (nplanes == 3 && bits_per_pixel == 8) {
         for (y = 0; y < h; y++) {
-            buf = pcx_rle_decode(buf, scanline, bytes_per_scanline, compressed);
+            buf = pcx_rle_decode(buf, buf_end,
+                                 scanline, bytes_per_scanline, compressed);
 
             for (x = 0; x < w; x++) {
                 ptr[3 * x]     = scanline[x];
@@ -165,7 +170,8 @@ static int pcx_decode_frame(AVCodecContext *avctx, void *data, int *got_frame,
         const uint8_t *palstart = bufstart + buf_size - 769;
 
         for (y = 0; y < h; y++, ptr += stride) {
-            buf = pcx_rle_decode(buf, scanline, bytes_per_scanline, compressed);
+            buf = pcx_rle_decode(buf, buf_end,
+                                 scanline, bytes_per_scanline, compressed);
             memcpy(ptr, scanline, w);
         }
 
@@ -183,7 +189,8 @@ static int pcx_decode_frame(AVCodecContext *avctx, void *data, int *got_frame,
         for (y = 0; y < h; y++) {
             init_get_bits(&s, scanline, bytes_per_scanline << 3);
 
-            buf = pcx_rle_decode(buf, scanline, bytes_per_scanline, compressed);
+            buf = pcx_rle_decode(buf, buf_end,
+                                 scanline, bytes_per_scanline, compressed);
 
             for (x = 0; x < w; x++)
                 ptr[x] = get_bits(&s, bits_per_pixel);
@@ -193,7 +200,8 @@ static int pcx_decode_frame(AVCodecContext *avctx, void *data, int *got_frame,
         int i;
 
         for (y = 0; y < h; y++) {
-            buf = pcx_rle_decode(buf, scanline, bytes_per_scanline, compressed);
+            buf = pcx_rle_decode(buf, buf_end,
+                                 scanline, bytes_per_scanline, compressed);
 
             for (x = 0; x < w; x++) {
                 int m = 0x80 >> (x & 7), v = 0;