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nscd: Skip unusable entries in first pass in prune_cache (RHEL-1192)

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Resolves: RHEL-1192
This commit is contained in:
Florian Weimer 2023-10-20 09:05:32 +02:00
parent 8514cc782e
commit 1ff30367b7
2 changed files with 88 additions and 1 deletions
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83
glibc-RHEL-1192.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 efe4214d953edb30..2fd3f78ebb567bbe 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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@ -1,6 +1,6 @@
%define glibcsrcdir glibc-2.28
%define glibcversion 2.28
%define glibcrelease 238%{?dist}
%define glibcrelease 239%{?dist}
# Pre-release tarballs are pulled in from git using a command that is
# effectively:
#
@ -1055,6 +1055,7 @@ Patch867: glibc-RHEL-2423.patch
Patch868: glibc-RHEL-3036.patch
Patch869: glibc-RHEL-3757.patch
Patch870: glibc-RHEL-2122.patch
Patch871: glibc-RHEL-1192.patch
##############################################################################
# Continued list of core "glibc" package information:
@ -2885,6 +2886,9 @@ fi
%files -f compat-libpthread-nonshared.filelist -n compat-libpthread-nonshared
%changelog
* Fri Oct 20 2023 Florian Weimer <fweimer@redhat.com> - 2.28-239
- nscd: Skip unusable entries in first pass in prune_cache (RHEL-1192)
* Mon Oct 16 2023 DJ Delorie <dj@redhat.com> - 2.28-238
- Fix slow tls access after dlopen (RHEL-2122)