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Fix data race in nscd (#806070)

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This commit is contained in:
Jeff Law 2012-03-29 10:25:56 -06:00
parent ccb21a9b27
commit d004e5468f
2 changed files with 57 additions and 3 deletions
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48
glibc-rh806070.patch Normal file
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@ -0,0 +1,48 @@
diff -rup c/nscd/nscd_gethst_r.c d/nscd/nscd_gethst_r.c
--- c/nscd/nscd_gethst_r.c 2012-01-01 05:16:32.000000000 -0700
+++ d/nscd/nscd_gethst_r.c 2012-03-28 10:45:51.546600822 -0600
@@ -101,9 +101,27 @@ 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;
+ int cnt = 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. */
+ while (__builtin_expect
+ (atomic_compare_and_exchange_val_acq (&__hst_map_handle.lock,
+ 1, 0) != 0, 0))
+ {
+ // XXX Best number of rounds?
+ if (__builtin_expect (++cnt > 5, 0))
+ return 0;
+
+ atomic_delay ();
+ }
+
struct mapped_database *map = __hst_map_handle.mapped;
if (map == NULL
@@ -113,9 +131,14 @@ __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;
}

12
glibc.spec
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@ -28,7 +28,7 @@
Summary: The GNU libc libraries
Name: glibc
Version: %{glibcversion}
Release: 29%{?dist}
Release: 30%{?dist}
# GPLv2+ is used in a bunch of programs, LGPLv2+ is used for libraries.
# Things that are linked directly into dynamically linked programs
# and shared libraries (e.g. crt files, lib*_nonshared.a) have an additional
@ -100,9 +100,9 @@ Patch32 : %{name}-rh739743.patch
Patch33 : %{name}-rh789238.patch
# From upstream
Patch34 : %{name}-rh794797.patch
# Posted upstream
# From upstream
Patch35 : %{name}-rh788989.patch
# Posted upstream
# From upstream (sans comment which was added during review)
Patch36 : %{name}-rh795498.patch
# From upstream
Patch37 : %{name}-rh760935.patch
@ -123,6 +123,8 @@ Patch44 : %{name}-stap-libm.patch
Patch45 : %{name}-rh803286.patch
# Sent upstream, waiting on review
Patch46 : %{name}-rh806403.patch
# Submitted upstream, BZ 13594
Patch47 : %{name}-rh806070.patch
Buildroot: %{_tmppath}/%{name}-%{version}-%{release}-root-%(%{__id_u} -n)
@ -388,6 +390,7 @@ rm -rf %{glibcportsdir}
%patch44 -p1
%patch45 -p1
%patch46 -p1
%patch47 -p1
# A lot of programs still misuse memcpy when they have to use
# memmove. The memcpy implementation below is not tolerant at
@ -1240,6 +1243,9 @@ rm -f *.filelist*
%endif
%changelog
* Tue Mar 27 2012 Jeff Law <law@redhat.com> - 2.15-30
- Fix data race in nscd (#806070)
* Fri Mar 23 2012 Jeff Law <law@redhat.com> - 2.15-29
- Fix typo in __nss_getent (#806403).