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ovsdb: Make "ovsdb-tool create" work through a dangling symlink.

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open() with O_CREAT|O_EXCL yields EEXIST if the name passed in is a
symlink, but we would like "ovsdb-tool create /etc/openvswitch/conf.db" to
work if /etc/openvswitch/conf.db is a symlink to elsewhere in the file
system.  This commit fixes the problem.  It introduces a theoretical race,
but no one should be doing "ovsdb-tool create" in parallel anyhow; O_EXCL
is just an idiot check here, not required to be fail-safe.

Debian bug #681880.
CC: 681880@bugs.debian.org
Reported-by: Bastian Blank <waldi@debian.org>
Signed-off-by: Ben Pfaff <blp@nicira.com>
Reviewed-by: Simon Horman <horms@verge.net.au>
This commit is contained in:
Ben Pfaff
2012-07-26 14:42:58 -07:00
parent 77c513a44a
commit 01ca539f5c
1 changed files with 11 additions and 2 deletions
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13
ovsdb/log.c
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@@ -1,4 +1,4 @@
/* Copyright (c) 2009, 2010, 2011 Nicira, Inc. /* Copyright (c) 2009, 2010, 2011, 2012 Nicira, Inc.
* *
* Licensed under the Apache License, Version 2.0 (the "License"); * Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License. * you may not use this file except in compliance with the License.
@@ -95,7 +95,16 @@ ovsdb_log_open(const char *name, enum ovsdb_log_open_mode open_mode,
} else if (open_mode == OVSDB_LOG_READ_WRITE) { } else if (open_mode == OVSDB_LOG_READ_WRITE) {
flags = O_RDWR; flags = O_RDWR;
} else if (open_mode == OVSDB_LOG_CREATE) { } else if (open_mode == OVSDB_LOG_CREATE) {
flags = O_RDWR | O_CREAT | O_EXCL; if (stat(name, &s) == -1 && errno == ENOENT
&& lstat(name, &s) == 0 && S_ISLNK(s.st_mode)) {
/* 'name' is a dangling symlink. We want to create the file that
* the symlink points to, but POSIX says that open() with O_EXCL
* must fail with EEXIST if the named file is a symlink. So, we
* have to leave off O_EXCL and accept the race. */
flags = O_RDWR | O_CREAT;
} else {
flags = O_RDWR | O_CREAT | O_EXCL;
}
} else { } else {
NOT_REACHED(); NOT_REACHED();
} }