From 50ed76deb2c88d37e506c2bca11556899b6c69df Mon Sep 17 00:00:00 2001
From: Rob Landley <rob@landley.net>
Date: Mon, 26 Dec 2022 12:02:05 -0600
Subject: [PATCH] Placate ASAN by replacing memcmp() with xmemcmp().

---
 lib/env.c               |  2 +-
 lib/lib.c               |  2 +-
 lib/lib.h               |  1 +
 lib/xwrap.c             | 11 ++++++++
 toys/other/hexedit.c    |  2 +-
 toys/other/nbd_client.c |  2 +-
 toys/other/readelf.c    |  4 +--
 toys/other/taskset.c    |  2 +-
 toys/posix/cpio.c       |  2 +-
 toys/posix/file.c       | 58 ++++++++++++++++++++---------------------
 toys/posix/od.c         |  2 +-
 toys/posix/ps.c         |  2 +-
 toys/posix/tar.c        |  2 +-
 13 files changed, 52 insertions(+), 40 deletions(-)

diff --git a/lib/env.c b/lib/env.c
index facde63f..7bcf5103 100644
--- a/lib/env.c
+++ b/lib/env.c
@@ -61,7 +61,7 @@ char *xsetenv(char *name, char *val)
 
   for (i = 0; environ[i]; i++) {
     // Drop old entry, freeing as appropriate. Assumes no duplicates.
-    if (!memcmp(name, environ[i], len) && environ[i][len]=='=') {
+    if (!xmemcmp(name, environ[i], len) && environ[i][len]=='=') {
       if (i<toys.envc-1) toys.envc--;
       else free(environ[i]);
       j++;
diff --git a/lib/lib.c b/lib/lib.c
index 1db31711..8d997da7 100644
--- a/lib/lib.c
+++ b/lib/lib.c
@@ -1492,7 +1492,7 @@ int is_tar_header(void *pkt)
   char *p = pkt;
   int i = 0;
 
-  if (p[257] && memcmp("ustar", p+257, 5)) return 0;
+  if (p[257] && xmemcmp("ustar", p+257, 5)) return 0;
   if (p[148] != '0' && p[148] != ' ') return 0;
   sscanf(p+148, "%8o", &i);
 
diff --git a/lib/lib.h b/lib/lib.h
index 2be31469..593ac3b2 100644
--- a/lib/lib.h
+++ b/lib/lib.h
@@ -103,6 +103,7 @@ struct dirtree *dirtree_read(char *path, int (*callback)(struct dirtree *node));
 #define ABS_LAST 8 // don't resolve symlink in last path component
 
 // xwrap.c
+int xmemcmp(char *one, char *two, unsigned long len);
 void xstrncpy(char *dest, char *src, size_t size);
 void xstrncat(char *dest, char *src, size_t size);
 _Noreturn void _xexit(void);
diff --git a/lib/xwrap.c b/lib/xwrap.c
index 0ca2346d..e1d242ff 100644
--- a/lib/xwrap.c
+++ b/lib/xwrap.c
@@ -9,6 +9,17 @@
 
 #include "toys.h"
 
+// ASAN flips out about memcmp("a", "abc", 4) but the result is well-defined.
+// This one's guaranteed to stop at len _or_ the first difference.
+int xmemcmp(char *one, char *two, unsigned long len)
+{
+  int ii = 0;
+
+  while (len--) if ((ii = *one++ - *two++)) break;
+
+  return ii;
+}
+
 // strcpy and strncat with size checking. Size is the total space in "dest",
 // including null terminator. Exit if there's not enough space for the string
 // (including space for the null terminator), because silently truncating is
diff --git a/toys/other/hexedit.c b/toys/other/hexedit.c
index d3402056..2b8f632a 100644
--- a/toys/other/hexedit.c
+++ b/toys/other/hexedit.c
@@ -181,7 +181,7 @@ static void find_prev(int pos)
   size_t len = strlen(TT.search);
 
   for (; pos >= 0; pos--) {
-    if (!memcmp(TT.data+pos, TT.search, len)) {
+    if (!xmemcmp(TT.data+pos, TT.search, len)) {
       TT.pos = pos;
       return;
     }
diff --git a/toys/other/nbd_client.c b/toys/other/nbd_client.c
index ad3440af..262bc0ce 100644
--- a/toys/other/nbd_client.c
+++ b/toys/other/nbd_client.c
@@ -59,7 +59,7 @@ void nbd_client_main(void)
     // Read login data
 
     xreadall(sock, toybuf, 152);
-    if (memcmp(toybuf, "NBDMAGIC\x00\x00\x42\x02\x81\x86\x12\x53", 16))
+    if (xmemcmp(toybuf, "NBDMAGIC\x00\x00\x42\x02\x81\x86\x12\x53", 16))
       error_exit("bad login %s:%s", host, port);
     devsize = SWAP_BE64(*(uint64_t *)(toybuf+16));
     flags = SWAP_BE32(*(int *)(toybuf+24));
diff --git a/toys/other/readelf.c b/toys/other/readelf.c
index 29e27244..6d01190b 100644
--- a/toys/other/readelf.c
+++ b/toys/other/readelf.c
@@ -355,7 +355,7 @@ static void scan_elf()
   char *hdr = TT.elf;
   int type, machine, version, flags, entry, ehsize, phnum, shstrndx, i, j, w;
 
-  if (TT.size < 45 || memcmp(hdr, "\177ELF", 4)) 
+  if (TT.size < 45 || xmemcmp(hdr, "\177ELF", 4))
     return error_msg("%s: not ELF", TT.f);
 
   TT.bits = hdr[4] - 1;
@@ -453,7 +453,7 @@ static void scan_elf()
              s.entsize, sh_flags, s.link, s.info, s.addralign);
     }
   }
-  if (FLAG(S) && TT.shnum) 
+  if (FLAG(S) && TT.shnum)
     printf("Key:\n  (W)rite, (A)lloc, e(X)ecute, (M)erge, (S)trings, (I)nfo\n"
            "  (L)ink order, (O)S, (G)roup, (T)LS, (C)ompressed, x=unknown\n");
 
diff --git a/toys/other/taskset.c b/toys/other/taskset.c
index 8af7cd19..7ca26490 100644
--- a/toys/other/taskset.c
+++ b/toys/other/taskset.c
@@ -127,7 +127,7 @@ void nproc_main(void)
     char *ss;
 
     while ((de = readdir(dd))) {
-      if (memcmp(de->d_name, "cpu", 3)) continue;
+      if (xmemcmp(de->d_name, "cpu", 3)) continue;
       for (ss = de->d_name+3; isdigit(*ss); ss++);
       if (!*ss) nproc++;
     }
diff --git a/toys/posix/cpio.c b/toys/posix/cpio.c
index 5ecd56df..b5542000 100644
--- a/toys/posix/cpio.c
+++ b/toys/posix/cpio.c
@@ -132,7 +132,7 @@ void cpio_main(void)
       if (empty) error_exit("empty archive");
       else break;
     }
-    if (size != 110 || memcmp(toybuf, "070701", 6)) error_exit("bad header");
+    if (size != 110 || xmemcmp(toybuf, "070701", 6)) error_exit("bad header");
     tofree = name = strpad(afd, x8u(toybuf+94), 110);
     if (!strcmp("TRAILER!!!", name)) {
       free(tofree);
diff --git a/toys/posix/file.c b/toys/posix/file.c
index e7b989b9..acfd28da 100644
--- a/toys/posix/file.c
+++ b/toys/posix/file.c
@@ -177,10 +177,10 @@ static void do_elf_file(int fd)
           goto bad;
         }
 
-        if (n_namesz==4 && !memcmp(note+12, "GNU", 4) && n_type==3) {
+        if (n_namesz==4 && !xmemcmp(note+12, "GNU", 4) && n_type==3) {
           printf(", BuildID=");
           for (j = 0; j<n_descsz; j++) printf("%02x", note[16+j]);
-        } else if (n_namesz==8 && !memcmp(note+12, "Android", 8)) {
+        } else if (n_namesz==8 && !xmemcmp(note+12, "Android", 8)) {
           if (n_type==1 /*.android.note.ident*/ && n_descsz >= 4) {
             printf(", for Android %d", (int)elf_int(note+20, 4));
             // NDK r14 and later also include NDK version info. OS binaries
@@ -244,7 +244,7 @@ static void do_regular_file(int fd, char *name)
       s-3, (int)peek_le(s, 2), (int)peek_le(s+2, 2));
 
   // TODO: parsing JPEG for width/height is harder than GIF or PNG.
-  else if (len>32 && !memcmp(s, "\xff\xd8", 2)) xputs("JPEG image data");
+  else if (len>32 && !xmemcmp(s, "\xff\xd8", 2)) xputs("JPEG image data");
 
   else if (len>8 && strstart(&s, "\xca\xfe\xba\xbe")) {
     unsigned count = peek_be(s, 4), i, arch;
@@ -307,7 +307,7 @@ static void do_regular_file(int fd, char *name)
   else if (len>31 && peek_be(s, 7) == 0xfd377a585a0000UL)
     xputs("xz compressed data");
   else if (len>10 && strstart(&s, "\x1f\x8b")) xputs("gzip compressed data");
-  else if (len>32 && !memcmp(s+1, "\xfa\xed\xfe", 3)) {
+  else if (len>32 && !xmemcmp(s+1, "\xfa\xed\xfe", 3)) {
     int bit = (*s==0xce) ? 32 : 64;
     char *what = 0;
 
@@ -325,26 +325,26 @@ static void do_regular_file(int fd, char *name)
     else what = NULL;
     if (what) xprintf("%s\n", what);
     else xprintf("(bad type %d)\n", s[9]);
-  } else if (len>36 && !memcmp(s, "OggS\x00\x02", 6)) {
+  } else if (len>36 && !xmemcmp(s, "OggS\x00\x02", 6)) {
     xprintf("Ogg data");
     // https://wiki.xiph.org/MIMETypesCodecs
-    if (!memcmp(s+28, "CELT    ", 8)) xprintf(", celt audio");
-    else if (!memcmp(s+28, "CMML    ", 8)) xprintf(", cmml text");
-    else if (!memcmp(s+28, "BBCD\0", 5)) xprintf(", dirac video");
-    else if (!memcmp(s+28, "\177FLAC", 5)) xprintf(", flac audio");
-    else if (!memcmp(s+28, "\x8bJNG\r\n\x1a\n", 8)) xprintf(", jng video");
-    else if (!memcmp(s+28, "\x80kate\0\0\0", 8)) xprintf(", kate text");
-    else if (!memcmp(s+28, "OggMIDI\0", 8)) xprintf(", midi text");
-    else if (!memcmp(s+28, "\x8aMNG\r\n\x1a\n", 8)) xprintf(", mng video");
-    else if (!memcmp(s+28, "OpusHead", 8)) xprintf(", opus audio");
-    else if (!memcmp(s+28, "PCM     ", 8)) xprintf(", pcm audio");
-    else if (!memcmp(s+28, "\x89PNG\r\n\x1a\n", 8)) xprintf(", png video");
-    else if (!memcmp(s+28, "Speex   ", 8)) xprintf(", speex audio");
-    else if (!memcmp(s+28, "\x80theora", 7)) xprintf(", theora video");
-    else if (!memcmp(s+28, "\x01vorbis", 7)) xprintf(", vorbis audio");
-    else if (!memcmp(s+28, "YUV4MPEG", 8)) xprintf(", yuv4mpeg video");
+    if (!xmemcmp(s+28, "CELT    ", 8)) xprintf(", celt audio");
+    else if (!xmemcmp(s+28, "CMML    ", 8)) xprintf(", cmml text");
+    else if (!xmemcmp(s+28, "BBCD\0", 5)) xprintf(", dirac video");
+    else if (!xmemcmp(s+28, "\177FLAC", 5)) xprintf(", flac audio");
+    else if (!xmemcmp(s+28, "\x8bJNG\r\n\x1a\n", 8)) xprintf(", jng video");
+    else if (!xmemcmp(s+28, "\x80kate\0\0\0", 8)) xprintf(", kate text");
+    else if (!xmemcmp(s+28, "OggMIDI\0", 8)) xprintf(", midi text");
+    else if (!xmemcmp(s+28, "\x8aMNG\r\n\x1a\n", 8)) xprintf(", mng video");
+    else if (!xmemcmp(s+28, "OpusHead", 8)) xprintf(", opus audio");
+    else if (!xmemcmp(s+28, "PCM     ", 8)) xprintf(", pcm audio");
+    else if (!xmemcmp(s+28, "\x89PNG\r\n\x1a\n", 8)) xprintf(", png video");
+    else if (!xmemcmp(s+28, "Speex   ", 8)) xprintf(", speex audio");
+    else if (!xmemcmp(s+28, "\x80theora", 7)) xprintf(", theora video");
+    else if (!xmemcmp(s+28, "\x01vorbis", 7)) xprintf(", vorbis audio");
+    else if (!xmemcmp(s+28, "YUV4MPEG", 8)) xprintf(", yuv4mpeg video");
     xputc('\n');
-  } else if (len>32 && !memcmp(s, "RIF", 3) && !memcmp(s+8, "WAVEfmt ", 8)) {
+  } else if (len>32 && !xmemcmp(s, "RIF", 3) && !xmemcmp(s+8, "WAVEfmt ", 8)) {
     // https://en.wikipedia.org/wiki/WAV
     int le = (s[3] == 'F');
     int format = le ? peek_le(s+20, 2) : peek_be(s+20, 2);
@@ -372,7 +372,7 @@ static void do_regular_file(int fd, char *name)
     else xprintf("unknown format %d", format);
     xputc('\n');
   } else if (len>12 && peek_be(s, 4)==0x10000) xputs("TrueType font");
-  else if (len>12 && !memcmp(s, "ttcf\x00", 5)) {
+  else if (len>12 && !xmemcmp(s, "ttcf\x00", 5)) {
     xprintf("TrueType font collection, version %d, %d fonts\n",
             (int)peek_be(s+4, 2), (int)peek_be(s+8, 4));
 
@@ -382,14 +382,14 @@ static void do_regular_file(int fd, char *name)
   else if (strstart(&s,"-----BEGIN CERTIFICATE-----")) xputs("PEM certificate");
 
   // https://msdn.microsoft.com/en-us/library/windows/desktop/ms680547(v=vs.85).aspx
-  else if (len>0x70 && !memcmp(s, "MZ", 2) &&
-      (magic=peek_le(s+0x3c,4))<len-4 && !memcmp(s+magic, "\x50\x45\0", 4)) {
+  else if (len>0x70 && !xmemcmp(s, "MZ", 2) &&
+      (magic=peek_le(s+0x3c,4))<len-4 && !xmemcmp(s+magic, "\x50\x45\0", 4)) {
 
     // Linux kernel images look like PE files.
     // https://www.kernel.org/doc/Documentation/arm64/booting.txt
     // I've only ever seen LE, 4KiB pages, so ignore flags for now.
-    if (!memcmp(s+0x38, "ARMd", 4)) return xputs("Linux arm64 kernel image");
-    else if (!memcmp(s+0x202, "HdrS", 4)) {
+    if (!xmemcmp(s+0x38, "ARMd", 4)) return xputs("Linux arm64 kernel image");
+    else if (!xmemcmp(s+0x202, "HdrS", 4)) {
       // https://www.kernel.org/doc/Documentation/x86/boot.txt
       unsigned ver_off = peek_le(s+0x20e, 2);
 
@@ -418,7 +418,7 @@ static void do_regular_file(int fd, char *name)
     xprintf("x86%s\n", (peek_le(s+magic+4, 2)==0x14c) ? "" : "-64");
 
     // https://en.wikipedia.org/wiki/BMP_file_format
-  } else if (len>0x32 && !memcmp(s, "BM", 2) && !peek_be(s+6, 4)) {
+  } else if (len>0x32 && !xmemcmp(s, "BM", 2) && !peek_be(s+6, 4)) {
     xprintf("BMP image, %d x %d, %d bpp\n", (int)peek_le(s+18, 4),
             (int)peek_le(s+22,4), (int)peek_le(s+28, 2));
 
@@ -432,7 +432,7 @@ static void do_regular_file(int fd, char *name)
         (int)peek_le(s+12, 4), (int)peek_le(s+20, 4));
 
     // https://android.googlesource.com/platform/system/tools/mkbootimg/+/refs/heads/master/include/bootimg/bootimg.h
-  } else if (len>1632 && !memcmp(s, "ANDROID!", 8)) {
+  } else if (len>1632 && !xmemcmp(s, "ANDROID!", 8)) {
     xprintf("Android boot image v%d\n", (int)peek_le(s+40, 4));
 
     // https://source.android.com/devices/architecture/dto/partitions
@@ -441,7 +441,7 @@ static void do_regular_file(int fd, char *name)
             (int)peek_be(s+16, 4));
 
     // frameworks/base/core/java/com/android/internal/util/BinaryXmlSerializer.java
-  } else if (len>4 && !memcmp(s, "ABX", 3)) {
+  } else if (len>4 && !xmemcmp(s, "ABX", 3)) {
     xprintf("Android Binary XML v%d\n", s[3]);
 
     // Text files, including shell scripts.
diff --git a/toys/posix/od.c b/toys/posix/od.c
index ffeb0d66..a37186cb 100644
--- a/toys/posix/od.c
+++ b/toys/posix/od.c
@@ -133,7 +133,7 @@ static void od_outline(void)
 
   // Handle duplciate lines as *
   if (!FLAG(v) && TT.j != TT.pos && TT.leftover
-    && !memcmp(TT.bufs[0], TT.bufs[1], TT.w))
+    && !xmemcmp(TT.bufs[0], TT.bufs[1], TT.w))
   {
     if (!TT.star) {
       xputs("*");
diff --git a/toys/posix/ps.c b/toys/posix/ps.c
index d6a3fce3..9033cdbd 100644
--- a/toys/posix/ps.c
+++ b/toys/posix/ps.c
@@ -845,7 +845,7 @@ static int get_ps(struct dirtree *new)
     off_t temp = 6;
 
     sprintf(buf, "%lld/exe", slot[SLOT_tid]);
-    if (readfileat(fd, buf, buf, &temp) && !memcmp(buf, "\177ELF", 4)) {
+    if (readfileat(fd, buf, buf, &temp) && !xmemcmp(buf, "\177ELF", 4)) {
       if (buf[4] == 1) slot[SLOT_bits] = 32;
       else if (buf[4] == 2) slot[SLOT_bits] = 64;
     }
diff --git a/toys/posix/tar.c b/toys/posix/tar.c
index 6f080689..aef1397b 100644
--- a/toys/posix/tar.c
+++ b/toys/posix/tar.c
@@ -990,7 +990,7 @@ void tar_main(void)
       if (len!=512 || !is_tar_header(hdr)) {
         // detect gzip and bzip signatures
         if (SWAP_BE16(*(short *)hdr)==0x1f8b) toys.optflags |= FLAG_z;
-        else if (!memcmp(hdr, "BZh", 3)) toys.optflags |= FLAG_j;
+        else if (!xmemcmp(hdr, "BZh", 3)) toys.optflags |= FLAG_j;
         else if (peek_be(hdr, 7) == 0xfd377a585a0000UL) toys.optflags |= FLAG_J;
         else error_exit("Not tar");
 
-- 
2.39.2