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authorAndreas Jaeger <aj@suse.de>2012-05-15 20:35:53 +0200
committerAndreas Jaeger <aj@suse.de>2012-05-15 20:37:05 +0200
commit509072a0f7f8a37bedf61a78c0cdd7783368c65a (patch)
tree32ac15ad1aba98673f42bc475d053fb1b4b3b864 /nscd/nscd_gethst_r.c
parentba75122dd93b6188d1be446df0502c4cbe5c32e6 (diff)
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Avoid race in nscd
2012-05-15 Jeff Law <law@redhat.com> Andreas Jaeger <aj@suse.de> [BZ #13594] * nscd/nscd-client.h (__nscd_acquire_maplock): New function, split out from... * nscd/nscd_helper.c (__nscd_get_map_ref): ... here. * nscd/nscd-client.h: Add __nscd_acquire_maplock. * nscd/nscd_gethst_r.c (__nscd_get_nl_timestamp): Add locking to code changing __hst_map_handle.map.
Diffstat (limited to 'nscd/nscd_gethst_r.c')
-rw-r--r--nscd/nscd_gethst_r.c21
1 files changed, 17 insertions, 4 deletions
diff --git a/nscd/nscd_gethst_r.c b/nscd/nscd_gethst_r.c
index c1661f86d4..d64ad2e7b6 100644
--- a/nscd/nscd_gethst_r.c
+++ b/nscd/nscd_gethst_r.c
@@ -1,5 +1,4 @@
-/* Copyright (C) 1998-2005, 2006, 2007, 2008, 2009, 2011
- Free Software Foundation, Inc.
+/* Copyright (C) 1998-2012 Free Software Foundation, Inc.
This file is part of the GNU C Library.
Contributed by Ulrich Drepper <drepper@cygnus.com>, 1998.
@@ -100,9 +99,18 @@ libc_freeres_fn (hst_map_free)
uint32_t
__nscd_get_nl_timestamp (void)
{
+ uint32_t retval;
if (__nss_not_use_nscd_hosts != 0)
return 0;
+ /* __nscd_get_mapping can change hst_map_handle.mapped to NO_MAPPING.
+ However, __nscd_get_mapping assumes the prior value was not NO_MAPPING.
+ Thus we have to acquire the lock to prevent this thread from changing
+ hst_map_handle.mapped to NO_MAPPING while another thread is inside
+ __nscd_get_mapping. */
+ if (!__nscd_acquire_maplock (&__hst_map_handle))
+ return 0;
+
struct mapped_database *map = __hst_map_handle.mapped;
if (map == NULL
@@ -112,9 +120,14 @@ __nscd_get_nl_timestamp (void)
map = __nscd_get_mapping (GETFDHST, "hosts", &__hst_map_handle.mapped);
if (map == NO_MAPPING)
- return 0;
+ retval = 0;
+ else
+ retval = map->head->extra_data[NSCD_HST_IDX_CONF_TIMESTAMP];
+
+ /* Release the lock. */
+ __hst_map_handle.lock = 0;
- return map->head->extra_data[NSCD_HST_IDX_CONF_TIMESTAMP];
+ return retval;
}