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nscd: Skip unusable entries in first pass in prune_cache (RHEL-3397)

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Resolves: RHEL-3397
This commit is contained in:
Florian Weimer 2023-10-20 10:43:51 +02:00
parent 01cc656c63
commit bab2bafb13
2 changed files with 88 additions and 1 deletions
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83
glibc-RHEL-3397.patch Normal file
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@ -0,0 +1,83 @@
commit c00b984fcd53f679ca2dafcd1aee2c89836e6e73
Author: Florian Weimer <fweimer@redhat.com>
Date: Tue Aug 29 08:28:31 2023 +0200
nscd: Skip unusable entries in first pass in prune_cache (bug 30800)
Previously, if an entry was marked unusable for any reason, but had
not timed out yet, the assert would trigger.
One way to get into such state is if a data change is detected during
re-validation of an entry. This causes the entry to be marked as not
usable. If exits nscd soon after that, then the clock jumps
backwards, and nscd restarted, the cache re-validation run after
startup triggers the removed assert.
The change is more complicated than just the removal of the assert
because entries marked as not usable should be garbage-collected in
the second pass. To make this happen, it is necessary to update some
book-keeping data.
Reviewed-by: DJ Delorie <dj@redhat.com>
diff --git a/nscd/cache.c b/nscd/cache.c
index 78b2269788699e6f..ac5902ae10b791bb 100644
--- a/nscd/cache.c
+++ b/nscd/cache.c
@@ -371,8 +371,11 @@ prune_cache (struct database_dyn *table, time_t now, int fd)
serv2str[runp->type], str, dh->timeout);
}
- /* Check whether the entry timed out. */
- if (dh->timeout < now)
+ /* Check whether the entry timed out. Timed out entries
+ will be revalidated. For unusable records, it is still
+ necessary to record that the bucket needs to be scanned
+ again below. */
+ if (dh->timeout < now || !dh->usable)
{
/* This hash bucket could contain entries which need to
be looked at. */
@@ -384,7 +387,7 @@ prune_cache (struct database_dyn *table, time_t now, int fd)
/* We only have to look at the data of the first entries
since the count information is kept in the data part
which is shared. */
- if (runp->first)
+ if (runp->first && dh->usable)
{
/* At this point there are two choices: we reload the
@@ -400,9 +403,6 @@ prune_cache (struct database_dyn *table, time_t now, int fd)
{
/* Remove the value. */
dh->usable = false;
-
- /* We definitely have some garbage entries now. */
- any = true;
}
else
{
@@ -414,18 +414,15 @@ prune_cache (struct database_dyn *table, time_t now, int fd)
time_t timeout = readdfcts[runp->type] (table, runp, dh);
next_timeout = MIN (next_timeout, timeout);
-
- /* If the entry has been replaced, we might need
- cleanup. */
- any |= !dh->usable;
}
}
+
+ /* If the entry has been replaced, we might need cleanup. */
+ any |= !dh->usable;
}
else
- {
- assert (dh->usable);
- next_timeout = MIN (next_timeout, dh->timeout);
- }
+ /* Entry has not timed out and is usable. */
+ next_timeout = MIN (next_timeout, dh->timeout);
run = runp->next;
}

6
glibc.spec
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@ -155,7 +155,7 @@ end \
Summary: The GNU libc libraries
Name: glibc
Version: %{glibcversion}
Release: 84%{?dist}
Release: 85%{?dist}
# In general, GPLv2+ is used by programs, LGPLv2+ is used for
# libraries.
@ -771,6 +771,7 @@ Patch534: glibc-RHEL-3000.patch
Patch535: glibc-RHEL-2426-14.patch
Patch536: glibc-RHEL-2426-15.patch
Patch537: glibc-RHEL-1191.patch
Patch538: glibc-RHEL-3397.patch
##############################################################################
# Continued list of core "glibc" package information:
@ -2928,6 +2929,9 @@ update_gconv_modules_cache ()
%endif
%changelog
* Fri Oct 20 2023 Florian Weimer <fweimer@redhat.com> - 2.34-85
- nscd: Skip unusable entries in first pass in prune_cache (RHEL-3397)
* Mon Oct 9 2023 Florian Weimer <fweimer@redhat.com> - 2.34-84
- x86-64: Report non-zero cache sizes under TDX hypervisors (RHEL-1191)