libextractor

commit f3397e43664392aa0f116f5de422b74fb820e3a3
parent e85307c7a13fc3348f0c0f3ab690186c60eaeaea
Author: Christian Grothoff <christian@grothoff.org>
Date:   Wed, 29 Jul 2026 11:06:16 +0200

fix integer underflow/overflow issues

Diffstat:
M
src/main/extractor_datasource.c
 | 
45
++++++++++++++++++++++++++++++---------------

1 file changed, 30 insertions(+), 15 deletions(-)
diff --git a/src/main/extractor_datasource.c b/src/main/extractor_datasource.c
@@ -355,12 +355,13 @@ bfds_seek (struct BufferedFileDataSource *bfds,
       LOG ("Invalid seek operation\n");
       return -1;
     }
-    if (bfds->fsize < -pos)
+    /* -pos is undefined for INT64_MIN; negate in unsigned arithmetic. */
+    if (bfds->fsize < (uint64_t) -(uint64_t) pos)
     {
       LOG ("Invalid seek operation\n");
       return -1;
     }
-    pos = bfds->fsize + pos;
+    pos = (int64_t) (bfds->fsize + (uint64_t) pos);
   /* fall-through! */
   case SEEK_SET:
     if (pos < 0)
@@ -1052,19 +1053,33 @@ cfs_seek (struct CompressedFileSource *cfs,
   switch (whence)
   {
   case SEEK_CUR:
-    if (cfs->fpos + position < 0)
+    if (position < 0)
     {
-      /* underflow */
-      LOG ("Invalid seek operation\n");
-      return -1;
+      /* underflow; -position is undefined for INT64_MIN, so the
+         magnitude is taken in unsigned arithmetic */
+      if ((uint64_t) cfs->fpos < (uint64_t) -(uint64_t) position)
+      {
+        LOG ("Invalid seek operation\n");
+        return -1;
+      }
     }
-    if ( (-1 != cfs->uncompressed_size) &&
-         (cfs->fpos + position > cfs->uncompressed_size) )
+    else
     {
-      LOG ("Invalid seek operation\n");
-      return -1;
+      /* the addition itself must not overflow, which it can whenever
+         the uncompressed size is still unknown */
+      if (position > INT64_MAX - cfs->fpos)
+      {
+        LOG ("Invalid seek operation\n");
+        return -1;
+      }
+      if ( (-1 != cfs->uncompressed_size) &&
+           (cfs->fpos + position > cfs->uncompressed_size) )
+      {
+        LOG ("Invalid seek operation\n");
+        return -1;
+      }
     }
-    nposition = cfs->fpos + position;
+    nposition = (uint64_t) (cfs->fpos + position);
     break;
   case SEEK_END:
     ASSERT (-1 != cfs->uncompressed_size);
@@ -1073,12 +1088,12 @@ cfs_seek (struct CompressedFileSource *cfs,
       LOG ("Invalid seek operation\n");
       return -1;
     }
-    if (cfs->uncompressed_size < -position)
+    if ((uint64_t) cfs->uncompressed_size < (uint64_t) -(uint64_t) position)
     {
       LOG ("Invalid seek operation\n");
       return -1;
     }
-    nposition = cfs->uncompressed_size + position;
+    nposition = (uint64_t) (cfs->uncompressed_size + position);
     break;
   case SEEK_SET:
     if (position < 0)
@@ -1098,10 +1113,10 @@ cfs_seek (struct CompressedFileSource *cfs,
     LOG ("Invalid seek operation\n");
     return -1;
   }
-  delta = nposition - cfs->fpos;
+  delta = (int64_t) (nposition - (uint64_t) cfs->fpos);
   if (delta < 0)
   {
-    if (cfs->result_pos >= -delta)
+    if ((uint64_t) cfs->result_pos >= (uint64_t) -(uint64_t) delta)
     {
       cfs->result_pos += delta;
       cfs->fpos += delta;