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Fix force-first handling in dlclose (RHEL-10481)

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Resolves: RHEL-10481
This commit is contained in:
Florian Weimer 2023-11-20 12:50:16 +01:00
parent cc28cc2e2a
commit 159c3a720f
2 changed files with 117 additions and 1 deletions
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112
glibc-RHEL-10481.patch Normal file
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@ -0,0 +1,112 @@
commit 849274d48fc59bfa6db3c713c8ced8026b20f3b7
Author: Florian Weimer <fweimer@redhat.com>
Date: Thu Nov 16 19:55:35 2023 +0100
elf: Fix force_first handling in dlclose (bug 30981)
The force_first parameter was ineffective because the dlclose'd
object was not necessarily the first in the maps array. Also
enable force_first handling unconditionally, regardless of namespace.
The initial object in a namespace should be destructed first, too.
The _dl_sort_maps_dfs function had early returns for relocation
dependency processing which broke force_first handling, too, and
this is fixed in this change as well.
Reviewed-by: Adhemerval Zanella <adhemerval.zanella@linaro.org>
diff --git a/elf/dl-close.c b/elf/dl-close.c
index 66524b6708c59f29..8107c2d5f6ad2bc6 100644
--- a/elf/dl-close.c
+++ b/elf/dl-close.c
@@ -182,6 +182,16 @@ _dl_close_worker (struct link_map *map, bool force)
}
assert (idx == nloaded);
+ /* Put the dlclose'd map first, so that its destructor runs first.
+ The map variable is NULL after a retry. */
+ if (map != NULL)
+ {
+ maps[map->l_idx] = maps[0];
+ maps[map->l_idx]->l_idx = map->l_idx;
+ maps[0] = map;
+ maps[0]->l_idx = 0;
+ }
+
/* Keep track of the lowest index link map we have covered already. */
int done_index = -1;
while (++done_index < nloaded)
@@ -255,9 +265,10 @@ _dl_close_worker (struct link_map *map, bool force)
}
}
- /* Sort the entries. We can skip looking for the binary itself which is
- at the front of the search list for the main namespace. */
- _dl_sort_maps (maps, nloaded, (nsid == LM_ID_BASE), true);
+ /* Sort the entries. Unless retrying, the maps[0] object (the
+ original argument to dlclose) needs to remain first, so that its
+ destructor runs first. */
+ _dl_sort_maps (maps, nloaded, /* force_first */ map != NULL, true);
/* Call all termination functions at once. */
bool unload_any = false;
@@ -768,7 +779,11 @@ _dl_close_worker (struct link_map *map, bool force)
/* Recheck if we need to retry, release the lock. */
out:
if (dl_close_state == rerun)
- goto retry;
+ {
+ /* The map may have been deallocated. */
+ map = NULL;
+ goto retry;
+ }
dl_close_state = not_pending;
}
diff --git a/elf/dl-sort-maps.c b/elf/dl-sort-maps.c
index aeb79b40b45054c0..c17ac325eca658ef 100644
--- a/elf/dl-sort-maps.c
+++ b/elf/dl-sort-maps.c
@@ -260,13 +260,12 @@ _dl_sort_maps_dfs (struct link_map **maps, unsigned int nmaps,
The below memcpy is not needed in the do_reldeps case here,
since we wrote back to maps[] during DFS traversal. */
if (maps_head == maps)
- return;
+ break;
}
assert (maps_head == maps);
- return;
}
-
- memcpy (maps, rpo, sizeof (struct link_map *) * nmaps);
+ else
+ memcpy (maps, rpo, sizeof (struct link_map *) * nmaps);
/* Skipping the first object at maps[0] is not valid in general,
since traversing along object dependency-links may "find" that
diff --git a/elf/dso-sort-tests-1.def b/elf/dso-sort-tests-1.def
index 4bf9052db16fb352..cf6453e9eb85ac65 100644
--- a/elf/dso-sort-tests-1.def
+++ b/elf/dso-sort-tests-1.def
@@ -56,14 +56,16 @@ output: b>a>{}<a<b
# relocation(dynamic) dependencies. While this is technically unspecified, the
# presumed reasonable practical behavior is for the destructor order to respect
# the static DT_NEEDED links (here this means the a->b->c->d order).
-# The older dynamic_sort=1 algorithm does not achieve this, while the DFS-based
-# dynamic_sort=2 algorithm does, although it is still arguable whether going
-# beyond spec to do this is the right thing to do.
+# The older dynamic_sort=1 algorithm originally did not achieve this,
+# but this was a bug in the way _dl_sort_maps was called from _dl_close_worker,
+# effectively disabling proper force_first handling.
+# The new dynamic_sort=2 algorithm shows the effect of the simpler force_first
+# handling: the a object is simply moved to the front.
# The below expected outputs are what the two algorithms currently produce
# respectively, for regression testing purposes.
tst-bz15311: {+a;+e;+f;+g;+d;%d;-d;-g;-f;-e;-a};a->b->c->d;d=>[ba];c=>a;b=>e=>a;c=>f=>b;d=>g=>c
-output(glibc.rtld.dynamic_sort=1): {+a[d>c>b>a>];+e[e>];+f[f>];+g[g>];+d[];%d(b(e(a()))a()g(c(a()f(b(e(a()))))));-d[];-g[];-f[];-e[];-a[<a<c<d<g<f<b<e];}
-output(glibc.rtld.dynamic_sort=2): {+a[d>c>b>a>];+e[e>];+f[f>];+g[g>];+d[];%d(b(e(a()))a()g(c(a()f(b(e(a()))))));-d[];-g[];-f[];-e[];-a[<g<f<a<b<c<d<e];}
+output(glibc.rtld.dynamic_sort=1): {+a[d>c>b>a>];+e[e>];+f[f>];+g[g>];+d[];%d(b(e(a()))a()g(c(a()f(b(e(a()))))));-d[];-g[];-f[];-e[];-a[<a<b<c<d<g<f<e];}
+output(glibc.rtld.dynamic_sort=2): {+a[d>c>b>a>];+e[e>];+f[f>];+g[g>];+d[];%d(b(e(a()))a()g(c(a()f(b(e(a()))))));-d[];-g[];-f[];-e[];-a[<a<g<f<b<c<d<e];}
# Test that even in the presence of dependency loops involving dlopen'ed
# object, that object is initialized last (and not unloaded prematurely).

6
glibc.spec
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@ -1,6 +1,6 @@
%define glibcsrcdir glibc-2.28
%define glibcversion 2.28
%define glibcrelease 241%{?dist}
%define glibcrelease 242%{?dist}
# Pre-release tarballs are pulled in from git using a command that is
# effectively:
#
@ -1057,6 +1057,7 @@ Patch869: glibc-RHEL-3757.patch
Patch870: glibc-RHEL-2122.patch
Patch871: glibc-RHEL-1192.patch
Patch872: glibc-RHEL-3639.patch
Patch873: glibc-RHEL-10481.patch
##############################################################################
# Continued list of core "glibc" package information:
@ -2888,6 +2889,9 @@ fi
%files -f compat-libpthread-nonshared.filelist -n compat-libpthread-nonshared
%changelog
* Mon Nov 20 2023 Florian Weimer <fweimer@redhat.com> - 2.28-242
- Fix force-first handling in dlclose (RHEL-10481)
* Fri Nov 10 2023 Florian Weimer <fweimer@redhat.com> - 2.28-241
- Avoid lazy binding failures during dlclose (RHEL-3639)