From 82dade88f04fe59290a7a9da305384e731eb8b6a Mon Sep 17 00:00:00 2001 From: Davi Arnaut Date: Fri, 7 Jan 2011 16:33:36 -0200 Subject: Bug#51023: Mysql server crashes on SIGHUP and destroys InnoDB files From a user perspective, the problem is that a FLUSH LOGS or SIGHUP signal could end up associating the stdout and stderr to random files. In the case of this bug report, the streams would end up associated to InnoDB ibd files. The freopen(3) function is not thread-safe on FreeBSD. What this means is that if another thread calls open(2) during freopen() is executing that another thread's fd returned by open(2) may get re-associated with the file being passed to freopen(3). See FreeBSD PR number 79887 for reference: http://www.freebsd.org/cgi/query-pr.cgi?pr=79887 This problem is worked around by substituting a internal hook within the FILE structure. This avoids the loss of atomicity by not having the original fd closed before its duplicated. Patch based on the original work by Vasil Dimov. include/my_sys.h: Export my_freopen. mysys/my_fopen.c: Add a my_freopen abstraction to workaround bugs in specific OSes. Add a prototype for getosreldate() as older FreeBSD versions did not define one. sql/log.cc: Move freopen abstraction code over to mysys. The streams are now only reopened for writing. --- mysys/my_fopen.c | 135 ++++++++++++++++++++++++++++++++++++++++++++++++++++++- 1 file changed, 134 insertions(+), 1 deletion(-) (limited to 'mysys/my_fopen.c') diff --git a/mysys/my_fopen.c b/mysys/my_fopen.c index 44156da6ae3..a822b63dd63 100644 --- a/mysys/my_fopen.c +++ b/mysys/my_fopen.c @@ -18,6 +18,10 @@ #include #include "mysys_err.h" +#if defined(__FreeBSD__) +extern int getosreldate(void); +#endif + static void make_ftype(char * to,int flag); /* @@ -97,8 +101,137 @@ FILE *my_fopen(const char *filename, int flags, myf MyFlags) } /* my_fopen */ - /* Close a stream */ +#if defined(_WIN32) + +static FILE *my_win_freopen(const char *path, FILE *stream) +{ + int handle_fd, fd= _fileno(stream); + HANDLE osfh; + + DBUG_ASSERT(filename && stream); + + /* Services don't have stdout/stderr on Windows, so _fileno returns -1. */ + if (fd < 0) + { + if (!freopen(filename, mode, stream)) + return NULL; + + fd= _fileno(stream); + } + + if ((osfh= CreateFile(path, GENERIC_READ | GENERIC_WRITE, + FILE_SHARE_READ | FILE_SHARE_WRITE | + FILE_SHARE_DELETE, NULL, + OPEN_ALWAYS, FILE_ATTRIBUTE_NORMAL, + NULL)) == INVALID_HANDLE_VALUE) + return NULL; + + if ((handle_fd= _open_osfhandle((intptr_t)osfh, + _O_APPEND | _O_TEXT)) == -1) + { + CloseHandle(osfh); + return NULL; + } + + if (_dup2(handle_fd, fd) < 0) + { + CloseHandle(osfh); + return NULL; + } + + _close(handle_fd); + + return stream; +} + +#elif defined(__FreeBSD__) + +/* No close operation hook. */ + +static int no_close(void *cookie __attribute__((unused))) +{ + return 0; +} + +/* + A hack around a race condition in the implementation of freopen. + + The race condition steams from the fact that the current fd of + the stream is closed before its number is used to duplicate the + new file descriptor. This defeats the desired atomicity of the + close and duplicate of dup2(). + + See PR number 79887 for reference: + http://www.freebsd.org/cgi/query-pr.cgi?pr=79887 +*/ + +static FILE *my_freebsd_freopen(const char *path, const char *mode, FILE *stream) +{ + int old_fd; + FILE *result; + + flockfile(stream); + + old_fd= fileno(stream); + + /* Use a no operation close hook to avoid having the fd closed. */ + stream->_close= no_close; + + /* Relies on the implicit dup2 to close old_fd. */ + result= freopen(path, mode, stream); + + /* If successful, the _close hook was replaced. */ + + if (result == NULL) + close(old_fd); + else + funlockfile(result); + + return result; +} + +#endif + + +/** + Change the file associated with a file stream. + + @param path Path to file. + @param mode Mode of the stream. + @param stream File stream. + + @note + This function is used to redirect stdout and stderr to a file and + subsequently to close and reopen that file for log rotation. + + @retval A FILE pointer on success. Otherwise, NULL. +*/ + +FILE *my_freopen(const char *path, const char *mode, FILE *stream) +{ + FILE *result; + +#if defined(_WIN32) + result= my_win_freopen(path, mode, stream); +#elif defined(__FreeBSD__) + /* + XXX: Once the fix is ported to the stable releases, this should + be dependent upon the specific FreeBSD versions. Check at: + http://www.freebsd.org/cgi/query-pr.cgi?pr=79887 + */ + if (getosreldate() > 900027) + result= freopen(path, mode, stream); + else + result= my_freebsd_freopen(path, mode, stream); +#else + result= freopen(path, mode, stream); +#endif + + return result; +} + +/* Close a stream */ int my_fclose(FILE *fd, myf MyFlags) { int err,file; -- cgit v1.2.1 From 960d355bad36217dc4d8d924fb0770fa79dad3f9 Mon Sep 17 00:00:00 2001 From: Davi Arnaut Date: Fri, 7 Jan 2011 17:28:06 -0200 Subject: Bug#51023: Mysql server crashes on SIGHUP and destroys InnoDB files WIN32 compilation fixes: define ETIMEDOUT only if not available and fix typos and add a missing parameter. --- mysys/my_fopen.c | 6 +++--- 1 file changed, 3 insertions(+), 3 deletions(-) (limited to 'mysys/my_fopen.c') diff --git a/mysys/my_fopen.c b/mysys/my_fopen.c index a822b63dd63..b8373ecb3ab 100644 --- a/mysys/my_fopen.c +++ b/mysys/my_fopen.c @@ -103,17 +103,17 @@ FILE *my_fopen(const char *filename, int flags, myf MyFlags) #if defined(_WIN32) -static FILE *my_win_freopen(const char *path, FILE *stream) +static FILE *my_win_freopen(const char *path, const char *mode, FILE *stream) { int handle_fd, fd= _fileno(stream); HANDLE osfh; - DBUG_ASSERT(filename && stream); + DBUG_ASSERT(path && stream); /* Services don't have stdout/stderr on Windows, so _fileno returns -1. */ if (fd < 0) { - if (!freopen(filename, mode, stream)) + if (!freopen(path, mode, stream)) return NULL; fd= _fileno(stream); -- cgit v1.2.1 From 7540fc7707acbbcb965bb55c477d5ba6f8861999 Mon Sep 17 00:00:00 2001 From: Karen Langford Date: Tue, 25 Jan 2011 15:42:40 +0100 Subject: Updating header copyright/README in source for 2011 --- mysys/my_fopen.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) (limited to 'mysys/my_fopen.c') diff --git a/mysys/my_fopen.c b/mysys/my_fopen.c index b8373ecb3ab..72991490d75 100644 --- a/mysys/my_fopen.c +++ b/mysys/my_fopen.c @@ -1,4 +1,4 @@ -/* Copyright (C) 2000 MySQL AB +/* Copyright (c) 2000, 2011, Oracle and/or its affiliates. All rights reserved. This program is free software; you can redistribute it and/or modify it under the terms of the GNU General Public License as published by -- cgit v1.2.1