From: Nathan Moinvaziri <nathan@nathanm.com>
Date: Mon, 11 Apr 2022 02:35:12 +0000 (-0700)
Subject: Use _msan_unposion to unposion end of window for when it needs to read the past ... 
X-Git-Tag: 2.1.0-beta1~273
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=c882034d48afc0b32a38e8f7ca63a2e4e91ab42d;p=thirdparty%2Fzlib-ng.git

Use _msan_unposion to unposion end of window for when it needs to read the past < chunksize bytes in the window. See #1245.

Co-authored-by: Adam Stylinski <kungfujesus06@gmail.com>
---

diff --git a/inflate.c b/inflate.c
index 1a091485..291582d0 100644
--- a/inflate.c
+++ b/inflate.c
@@ -205,7 +205,12 @@ int Z_INTERNAL inflate_ensure_window(struct inflate_state *state) {
         state->window = (unsigned char *)ZALLOC_WINDOW(state->strm, wsize + state->chunksize, sizeof(unsigned char));
         if (state->window == NULL)
             return Z_MEM_ERROR;
-        memset(state->window + wsize, 0, state->chunksize);
+#ifdef Z_MEMORY_SANITIZER
+        /* This is _not_ to subvert the memory sanitizer but to instead unposion some
+           data we willingly and purposefully load uninitialized into vector registers
+           in order to safely read the last < chunksize bytes of the window. */
+        __msan_unpoison(state->window + wsize, state->chunksize);
+#endif
     }
 
     /* if window not in use yet, initialize */
diff --git a/zbuild.h b/zbuild.h
index f6923853..9274cbc1 100644
--- a/zbuild.h
+++ b/zbuild.h
@@ -246,4 +246,11 @@
 #  define zmemcmp_8(str1, str2) memcmp(str1, str2, 8)
 #endif
 
+#if defined(__has_feature)
+#  if __has_feature(memory_sanitizer)
+#    define Z_MEMORY_SANITIZER 1
+#    include <sanitizer/msan_interface.h>
+#  endif
+#endif
+
 #endif