113 lines
5.0 KiB
Diff
113 lines
5.0 KiB
Diff
commit 849274d48fc59bfa6db3c713c8ced8026b20f3b7
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Author: Florian Weimer <fweimer@redhat.com>
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Date: Thu Nov 16 19:55:35 2023 +0100
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elf: Fix force_first handling in dlclose (bug 30981)
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The force_first parameter was ineffective because the dlclose'd
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object was not necessarily the first in the maps array. Also
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enable force_first handling unconditionally, regardless of namespace.
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The initial object in a namespace should be destructed first, too.
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The _dl_sort_maps_dfs function had early returns for relocation
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dependency processing which broke force_first handling, too, and
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this is fixed in this change as well.
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Reviewed-by: Adhemerval Zanella <adhemerval.zanella@linaro.org>
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diff --git a/elf/dl-close.c b/elf/dl-close.c
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index 22225efb3226c3e1..16a39f5bf17b440f 100644
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--- a/elf/dl-close.c
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+++ b/elf/dl-close.c
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@@ -182,6 +182,16 @@ _dl_close_worker (struct link_map *map, bool force)
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}
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assert (idx == nloaded);
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+ /* Put the dlclose'd map first, so that its destructor runs first.
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+ The map variable is NULL after a retry. */
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+ if (map != NULL)
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+ {
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+ maps[map->l_idx] = maps[0];
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+ maps[map->l_idx]->l_idx = map->l_idx;
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+ maps[0] = map;
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+ maps[0]->l_idx = 0;
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+ }
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+
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/* Keep track of the lowest index link map we have covered already. */
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int done_index = -1;
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while (++done_index < nloaded)
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@@ -255,9 +265,10 @@ _dl_close_worker (struct link_map *map, bool force)
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}
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}
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- /* Sort the entries. We can skip looking for the binary itself which is
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- at the front of the search list for the main namespace. */
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- _dl_sort_maps (maps, nloaded, (nsid == LM_ID_BASE), true);
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+ /* Sort the entries. Unless retrying, the maps[0] object (the
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+ original argument to dlclose) needs to remain first, so that its
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+ destructor runs first. */
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+ _dl_sort_maps (maps, nloaded, /* force_first */ map != NULL, true);
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/* Call all termination functions at once. */
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bool unload_any = false;
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@@ -768,7 +779,11 @@ _dl_close_worker (struct link_map *map, bool force)
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/* Recheck if we need to retry, release the lock. */
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out:
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if (dl_close_state == rerun)
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- goto retry;
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+ {
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+ /* The map may have been deallocated. */
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+ map = NULL;
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+ goto retry;
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+ }
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dl_close_state = not_pending;
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}
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diff --git a/elf/dl-sort-maps.c b/elf/dl-sort-maps.c
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index aeb79b40b45054c0..c17ac325eca658ef 100644
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--- a/elf/dl-sort-maps.c
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+++ b/elf/dl-sort-maps.c
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@@ -260,13 +260,12 @@ _dl_sort_maps_dfs (struct link_map **maps, unsigned int nmaps,
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The below memcpy is not needed in the do_reldeps case here,
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since we wrote back to maps[] during DFS traversal. */
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if (maps_head == maps)
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- return;
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+ break;
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}
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assert (maps_head == maps);
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- return;
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}
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-
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- memcpy (maps, rpo, sizeof (struct link_map *) * nmaps);
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+ else
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+ memcpy (maps, rpo, sizeof (struct link_map *) * nmaps);
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/* Skipping the first object at maps[0] is not valid in general,
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since traversing along object dependency-links may "find" that
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diff --git a/elf/dso-sort-tests-1.def b/elf/dso-sort-tests-1.def
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index 4bf9052db16fb352..cf6453e9eb85ac65 100644
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--- a/elf/dso-sort-tests-1.def
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+++ b/elf/dso-sort-tests-1.def
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@@ -56,14 +56,16 @@ output: b>a>{}<a<b
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# relocation(dynamic) dependencies. While this is technically unspecified, the
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# presumed reasonable practical behavior is for the destructor order to respect
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# the static DT_NEEDED links (here this means the a->b->c->d order).
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-# The older dynamic_sort=1 algorithm does not achieve this, while the DFS-based
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-# dynamic_sort=2 algorithm does, although it is still arguable whether going
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-# beyond spec to do this is the right thing to do.
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+# The older dynamic_sort=1 algorithm originally did not achieve this,
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+# but this was a bug in the way _dl_sort_maps was called from _dl_close_worker,
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+# effectively disabling proper force_first handling.
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+# The new dynamic_sort=2 algorithm shows the effect of the simpler force_first
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+# handling: the a object is simply moved to the front.
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# The below expected outputs are what the two algorithms currently produce
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# respectively, for regression testing purposes.
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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
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-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];}
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-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];}
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+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];}
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+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];}
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# Test that even in the presence of dependency loops involving dlopen'ed
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# object, that object is initialized last (and not unloaded prematurely).
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