Date: Wed, 7 Aug 2019 20:13:43 +0000 (UTC) From: Dimitry Andric <dim@FreeBSD.org> To: src-committers@freebsd.org, svn-src-all@freebsd.org, svn-src-head@freebsd.org Subject: svn commit: r350697 - head/lib/libc/string Message-ID: <201908072013.x77KDhgM014931@repo.freebsd.org>
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Author: dim Date: Wed Aug 7 20:13:43 2019 New Revision: 350697 URL: https://svnweb.freebsd.org/changeset/base/350697 Log: Fix a possible segfault in wcsxfrm(3) and wcsxfrm_l(3). If the length of the source wide character string, passed in via the "size_t n" parameter, is set to zero, the function should only return the required length for the destination wide character string. In this case, it should *not* attempt to write to the destination, so the "dst" parameter is permitted to be NULL. However, when the internally called _collate_wxfrm() function returns an error, such as when using the "C" locale, as a fallback wcscpy(3) or wcsncpy(3) are used. But if the input length is zero, wcsncpy(3) will be called with a length of -1! If the "dst" parameter is NULL, this will immediately result in a segfault, or if "dst" is a valid pointer, it will most likely result in unexpectedly overwritten memory. Fix this by explicitly checking for an input length greater than zero, before calling wcsncpy(3). Note that a similar situation does not occur in strxfrm(3), the plain character version of this function, as it uses strlcpy(3) for the error case. The strlcpy(3) function does not write to the destination if the input length is zero. MFC after: 1 week Modified: head/lib/libc/string/wcsxfrm.c Modified: head/lib/libc/string/wcsxfrm.c ============================================================================== --- head/lib/libc/string/wcsxfrm.c Wed Aug 7 19:45:44 2019 (r350696) +++ head/lib/libc/string/wcsxfrm.c Wed Aug 7 20:13:43 2019 (r350697) @@ -73,7 +73,7 @@ error: slen = wcslen(src); if (slen < len) (void) wcscpy(dest, src); - else { + else if (len > 0) { (void) wcsncpy(dest, src, len - 1); dest[len - 1] = L'\0'; }
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