Fix possible infinite loop case when looking for a trailer.

Thanks to chibataiki for reporting and isolating this!
enferex · Apr 19, 2021 · 7e35d18 · 7e35d18
1 parent 8d07e05
commit 7e35d18
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diff --git a/AUTHORS b/AUTHORS
@@ -28,3 +28,5 @@ ZanderChang: Reported and identified bad code in kid page loading.
 yifengchen-cc: Reported a header parsing bug.
 
 kinzhong: Reported and isolated a xref scanning bug.
+
+chibataiki: Reported and isolated an infinite loop in the trailer search.
diff --git a/pdf.c b/pdf.c
@@ -726,7 +726,8 @@ static void get_xref_linear_skipped(FILE *fp, xref_t *xref)
     /* If we found 'trailer' look backwards for 'xref' */
     ch = 0;
     while (SAFE_F(fp, ((ch = fgetc(fp)) != 'x')))
-      fseek(fp, -2, SEEK_CUR);
+      if (fseek(fp, -2, SEEK_CUR) == -1)
+        FAIL("Failed to locate an xref.  This might be a corrupt PDF.\n");
 
     if (ch == 'x')
     {