Date: Sat, 11 Feb 2012 11:11:13 +0000 (UTC) From: Ed Schouten <ed@FreeBSD.org> To: src-committers@freebsd.org, svn-src-all@freebsd.org, svn-src-head@freebsd.org Subject: svn commit: r231514 - head/lib/libc/gen Message-ID: <201202111111.q1BBBDG3028340@svn.freebsd.org>
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Author: ed Date: Sat Feb 11 11:11:13 2012 New Revision: 231514 URL: http://svn.freebsd.org/changeset/base/231514 Log: Set read buffer size to multiple of sizeof(struct futx). If the utmpx database gets updated while an application is reading it, there is a chance the reading application processes partially overwritten entries. To solve this, make sure we always read a multiple of sizeof(struct futx) at a time. MFC after: 2 weeks Modified: head/lib/libc/gen/getutxent.c Modified: head/lib/libc/gen/getutxent.c ============================================================================== --- head/lib/libc/gen/getutxent.c Sat Feb 11 08:58:12 2012 (r231513) +++ head/lib/libc/gen/getutxent.c Sat Feb 11 11:11:13 2012 (r231514) @@ -70,13 +70,18 @@ setutxdb(int db, const char *file) if (uf == NULL) return (-1); - /* Safety check: never use broken files. */ - if (db != UTXDB_LOG && _fstat(fileno(uf), &sb) != -1 && - sb.st_size % sizeof(struct futx) != 0) { - fclose(uf); - uf = NULL; - errno = EFTYPE; - return (-1); + if (db != UTXDB_LOG) { + /* Safety check: never use broken files. */ + if (_fstat(fileno(uf), &sb) != -1 && + sb.st_size % sizeof(struct futx) != 0) { + fclose(uf); + uf = NULL; + errno = EFTYPE; + return (-1); + } + /* Prevent reading of partial records. */ + (void)setvbuf(uf, NULL, _IOFBF, + rounddown(BUFSIZ, sizeof(struct futx))); } udb = db;
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