Date: Sun, 21 Oct 2012 06:55:56 GMT From: Jukka Ukkonen <jau@iki.fi> To: freebsd-gnats-submit@FreeBSD.org Subject: kern/172921: O_CLOEXEC support for libdb / dbopen Message-ID: <201210210655.q9L6tuBL096387@red.freebsd.org> Resent-Message-ID: <201210210700.q9L701rl088072@freefall.freebsd.org>
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>Number: 172921
>Category: kern
>Synopsis: O_CLOEXEC support for libdb / dbopen
>Confidential: no
>Severity: non-critical
>Priority: low
>Responsible: freebsd-bugs
>State: open
>Quarter:
>Keywords:
>Date-Required:
>Class: change-request
>Submitter-Id: current-users
>Arrival-Date: Sun Oct 21 07:00:01 UTC 2012
>Closed-Date:
>Last-Modified:
>Originator: Jukka Ukkonen
>Release: 9.1-PRERELEASE
>Organization:
-----
>Environment:
FreeBSD sleipnir 9.1-PRERELEASE FreeBSD 9.1-PRERELEASE #0: Sun Oct 21 08:20:37 EEST 2012 root@sleipnir:/usr/obj/usr/src/sys/Sleipnir amd64
>Description:
Traditionally libdb has used fcntl() and FD_CLOEXEC to mark the files to be
closed when exec() is called.
If used in a threaded code this leaves a minimal time window during which
another thread could call exec() while the FD_CLOEXEC flag has not yet been set.
Using O_CLOEXEC with open() can be used to close the window on system which
support O_CLOEXEC.
The attached path amends libdb (the default version bundled with libc) to use
O_CLOEXEC whenever possible.
The patch also changes dbopen to allow setting O_DIRECT on those systems which support the flag.
>How-To-Repeat:
In fact the little time window is extremely hard to abuse intentionally.
>Fix:
Apply the attached patch.
Patch attached with submission follows:
--- lib/libc/db/btree/bt_open.c.orig 2012-10-21 09:03:10.000000000 +0300
+++ lib/libc/db/btree/bt_open.c 2012-10-21 09:05:16.000000000 +0300
@@ -196,6 +196,10 @@
goto einval;
}
+#if defined(O_CLOEXEC)
+ flags |= O_CLOEXEC;
+#endif
+
if ((t->bt_fd = _open(fname, flags, mode)) < 0)
goto err;
@@ -207,7 +211,10 @@
F_SET(t, B_INMEM);
}
- if (_fcntl(t->bt_fd, F_SETFD, 1) == -1)
+ /*
+ * Needed for the tmp() case and for systems without O_CLOEXEC.
+ */
+ if (_fcntl(t->bt_fd, F_SETFD, FD_CLOEXEC) == -1)
goto err;
if (_fstat(t->bt_fd, &sb))
--- lib/libc/db/hash/hash.c.orig 2012-10-21 09:08:49.000000000 +0300
+++ lib/libc/db/hash/hash.c 2012-10-21 09:10:30.000000000 +0300
@@ -108,6 +108,10 @@
return (NULL);
}
+#if defined(O_CLOEXEC)
+ flags |= O_CLOEXEC;
+#endif
+
if (!(hashp = (HTAB *)calloc(1, sizeof(HTAB))))
return (NULL);
hashp->fp = -1;
@@ -123,7 +127,9 @@
if (file) {
if ((hashp->fp = _open(file, flags, mode)) == -1)
RETURN_ERROR(errno, error0);
- (void)_fcntl(hashp->fp, F_SETFD, 1);
+#if !defined(O_CLOEXEC)
+ (void)_fcntl(hashp->fp, F_SETFD, FD_CLOEXEC);
+#endif
new_table = _fstat(hashp->fp, &statbuf) == 0 &&
statbuf.st_size == 0 && (flags & O_ACCMODE) != O_RDONLY;
} else
--- lib/libc/db/recno/rec_open.c.orig 2012-10-21 09:21:53.000000000 +0300
+++ lib/libc/db/recno/rec_open.c 2012-10-21 09:27:57.000000000 +0300
@@ -63,6 +63,10 @@
struct stat sb;
int rfd, sverrno;
+#if defined(O_CLOEXEC)
+ flags |= O_CLOEXEC;
+#endif
+
/* Open the user's file -- if this fails, we're done. */
if (fname != NULL && (rfd = _open(fname, flags, mode)) < 0)
return (NULL);
--- lib/libc/db/db/db.c.orig 2012-10-21 06:49:59.000000000 +0300
+++ lib/libc/db/db/db.c 2012-10-21 07:21:38.000000000 +0300
@@ -42,6 +42,20 @@
#include <db.h>
+/*
+ * Just so that the exact same USE_OPEN_FLAGS
+ * will work also on systems which do not have
+ * support for some common open() flags.
+ */
+
+#if !defined(O_CLOEXEC)
+# define O_CLOEXEC 0
+#endif
+
+#if !defined(O_DIRECT)
+# define O_DIRECT 0
+#endif
+
static int __dberr(void);
DB *
@@ -51,7 +65,8 @@
#define DB_FLAGS (DB_LOCK | DB_SHMEM | DB_TXN)
#define USE_OPEN_FLAGS \
(O_CREAT | O_EXCL | O_EXLOCK | O_NOFOLLOW | O_NONBLOCK | \
- O_RDONLY | O_RDWR | O_SHLOCK | O_SYNC | O_TRUNC)
+ O_RDONLY | O_RDWR | O_SHLOCK | O_SYNC | O_TRUNC | O_CLOEXEC | \
+ O_DIRECT )
if ((flags & ~(USE_OPEN_FLAGS | DB_FLAGS)) == 0)
switch (type) {
>Release-Note:
>Audit-Trail:
>Unformatted:
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