Mercurial > hg
changeset 24286:40528ad1b1e8
lazymanifest: don't depend on printf's 'hh' format to work
Where we convert a 20-byte binary to a 40-byte hex string in
lazymanifest_setitem(), we use sprintf("%02hhx", hash[i]). As Matt
Harbison found out, 'hh' seems to be ignored on some platforms (Visual
Studio?). If char is signed on such platforms, the value gets
sign-extended as it gets promoted into an int when passed into the
variadic sprintf(). The resulting integer value will then be printed
with leading f's (14 of them on 64-bit systems), since the '2' in the
format string indicates only minimum number of characters. This is
both incorrect and runs the risk of writing outside of allocated
memory (as Matt reported).
To fix, let's cast the value to unsigned char before passing it to
sprintf(). Also drop the poorly supported 'hh' formatting that now
becomes unnecessary.
| author | Martin von Zweigbergk <martinvonz@google.com> |
|---|---|
| date | Thu, 12 Mar 2015 09:06:45 -0700 |
| parents | 8e13cc0825f1 |
| children | f78252429e0a |
| files | mercurial/manifest.c |
| diffstat | 1 files changed, 4 insertions(+), 1 deletions(-) [+] |
line wrap: on
line diff
--- a/mercurial/manifest.c Wed Mar 11 17:53:50 2015 -0700 +++ b/mercurial/manifest.c Thu Mar 12 09:06:45 2015 -0700 @@ -466,7 +466,10 @@ } memcpy(dest, path, plen + 1); for (i = 0; i < 20; i++) { - sprintf(dest + plen + 1 + (i * 2), "%02hhx", hash[i]); + /* Cast to unsigned, so it will not get sign-extended when promoted + * to int (as is done when passing to a variadic function) + */ + sprintf(dest + plen + 1 + (i * 2), "%02x", (unsigned char)hash[i]); } memcpy(dest + plen + 41, flags, flen); dest[plen + 41 + flen] = '\n';