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DSO dependency sort must put new map first even if in cycle (#2128615)

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Resolves: #2128615
This commit is contained in:
Florian Weimer 2022-10-11 11:14:41 +02:00
parent 5a600889b6
commit 6656bd38ac
4 changed files with 213 additions and 1 deletions
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37
glibc-rh2128615-1.patch Normal file
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@ -0,0 +1,37 @@
commit 183d99737298bb3200f0610fdcd1c7549c8ed560
Author: Florian Weimer <fweimer@redhat.com>
Date: Tue Sep 6 07:38:10 2022 +0200
scripts/dso-ordering-test.py: Generate program run-time dependencies
The main program needs to depend on all shared objects, even objects
that have link-time dependencies among shared objects. Filtering
out shared objects that already have an link-time dependencies is not
necessary here; make will do this automatically.
Reviewed-by: Adhemerval Zanella <adhemerval.zanella@linaro.org>
diff --git a/scripts/dso-ordering-test.py b/scripts/dso-ordering-test.py
index bde0406be9da14fc..4ffcff6136145ef1 100644
--- a/scripts/dso-ordering-test.py
+++ b/scripts/dso-ordering-test.py
@@ -707,13 +707,12 @@ def process_testcase(t):
"\t$(compile.c) $(OUTPUT_OPTION)\n")
makefile.write (rule)
- not_depended_objs = find_objs_not_depended_on(test_descr)
- if not_depended_objs:
- depstr = ""
- for dep in not_depended_objs:
- depstr += (" $(objpfx)" + test_subdir + "/"
- + test_name + "-" + dep + ".so")
- makefile.write("$(objpfx)%s.out:%s\n" % (base_test_name, depstr))
+ # Ensure that all shared objects are built before running the
+ # test, whether there link-time dependencies or not.
+ depobjs = ["$(objpfx){}/{}-{}.so".format(test_subdir, test_name, dep)
+ for dep in test_descr.objs]
+ makefile.write("$(objpfx){}.out: {}\n".format(
+ base_test_name, " ".join(depobjs)))
# Add main executable to test-srcs
makefile.write("test-srcs += %s/%s\n" % (test_subdir, test_name))

79
glibc-rh2128615-2.patch Normal file
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@ -0,0 +1,79 @@
commit dbb75513f5cf9285c77c9e55777c5c35b653f890
Author: Florian Weimer <fweimer@redhat.com>
Date: Tue Sep 6 07:38:10 2022 +0200
elf: Rename _dl_sort_maps parameter from skip to force_first
The new implementation will not be able to skip an arbitrary number
of objects.
Reviewed-by: Adhemerval Zanella <adhemerval.zanella@linaro.org>
diff --git a/elf/dl-sort-maps.c b/elf/dl-sort-maps.c
index 72f4ff0e6eda3377..7c614bca5d8115c6 100644
--- a/elf/dl-sort-maps.c
+++ b/elf/dl-sort-maps.c
@@ -27,12 +27,12 @@
If FOR_FINI is true, this is called for finishing an object. */
static void
_dl_sort_maps_original (struct link_map **maps, unsigned int nmaps,
- unsigned int skip, bool for_fini)
+ bool force_first, bool for_fini)
{
/* Allows caller to do the common optimization of skipping the first map,
usually the main binary. */
- maps += skip;
- nmaps -= skip;
+ maps += force_first;
+ nmaps -= force_first;
/* A list of one element need not be sorted. */
if (nmaps <= 1)
@@ -182,7 +182,7 @@ dfs_traversal (struct link_map ***rpo, struct link_map *map,
static void
_dl_sort_maps_dfs (struct link_map **maps, unsigned int nmaps,
- unsigned int skip __attribute__ ((unused)), bool for_fini)
+ bool force_first __attribute__ ((unused)), bool for_fini)
{
for (int i = nmaps - 1; i >= 0; i--)
maps[i]->l_visited = 0;
@@ -286,7 +286,7 @@ _dl_sort_maps_init (void)
void
_dl_sort_maps (struct link_map **maps, unsigned int nmaps,
- unsigned int skip, bool for_fini)
+ bool force_first, bool for_fini)
{
/* It can be tempting to use a static function pointer to store and call
the current selected sorting algorithm routine, but experimentation
@@ -296,9 +296,9 @@ _dl_sort_maps (struct link_map **maps, unsigned int nmaps,
input cases. A simple if-case with direct function calls appears to
be the fastest. */
if (__glibc_likely (GLRO(dl_dso_sort_algo) == dso_sort_algorithm_original))
- _dl_sort_maps_original (maps, nmaps, skip, for_fini);
+ _dl_sort_maps_original (maps, nmaps, force_first, for_fini);
else
- _dl_sort_maps_dfs (maps, nmaps, skip, for_fini);
+ _dl_sort_maps_dfs (maps, nmaps, force_first, for_fini);
}
#endif /* HAVE_TUNABLES. */
diff --git a/sysdeps/generic/ldsodefs.h b/sysdeps/generic/ldsodefs.h
index 87ad2f3f4d89eb7d..8c0fe98f69a88f1e 100644
--- a/sysdeps/generic/ldsodefs.h
+++ b/sysdeps/generic/ldsodefs.h
@@ -1106,9 +1106,11 @@ extern void _dl_init (struct link_map *main_map, int argc, char **argv,
initializer functions have completed. */
extern void _dl_fini (void) attribute_hidden;
-/* Sort array MAPS according to dependencies of the contained objects. */
+/* Sort array MAPS according to dependencies of the contained objects.
+ If FORCE_FIRST, MAPS[0] keeps its place even if the dependencies
+ say otherwise. */
extern void _dl_sort_maps (struct link_map **maps, unsigned int nmaps,
- unsigned int skip, bool for_fini) attribute_hidden;
+ bool force_first, bool for_fini) attribute_hidden;
/* The dynamic linker calls this function before and having changing
any shared object mappings. The `r_state' member of `struct r_debug'

90
glibc-rh2128615-3.patch Normal file
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@ -0,0 +1,90 @@
commit 1df71d32fe5f5905ffd5d100e5e9ca8ad6210891
Author: Florian Weimer <fweimer@redhat.com>
Date: Tue Sep 20 11:00:42 2022 +0200
elf: Implement force_first handling in _dl_sort_maps_dfs (bug 28937)
The implementation in _dl_close_worker requires that the first
element of l_initfini is always this very map (“We are always the
zeroth entry, and since we don't include ourselves in the
dependency analysis start at 1.”). Rather than fixing that
assumption, this commit adds an implementation of the force_first
argument to the new dependency sorting algorithm. This also means
that the directly dlopen'ed shared object is always initialized last,
which is the least surprising behavior in the presence of cycles.
Reviewed-by: Adhemerval Zanella <adhemerval.zanella@linaro.org>
diff --git a/elf/dl-sort-maps.c b/elf/dl-sort-maps.c
index 7c614bca5d8115c6..e8ef5e8b3588ab53 100644
--- a/elf/dl-sort-maps.c
+++ b/elf/dl-sort-maps.c
@@ -182,8 +182,9 @@ dfs_traversal (struct link_map ***rpo, struct link_map *map,
static void
_dl_sort_maps_dfs (struct link_map **maps, unsigned int nmaps,
- bool force_first __attribute__ ((unused)), bool for_fini)
+ bool force_first, bool for_fini)
{
+ struct link_map *first_map = maps[0];
for (int i = nmaps - 1; i >= 0; i--)
maps[i]->l_visited = 0;
@@ -208,14 +209,6 @@ _dl_sort_maps_dfs (struct link_map **maps, unsigned int nmaps,
Adjusting the order so that maps[0] is last traversed naturally avoids
this problem.
- Further, the old "optimization" of skipping the main object at maps[0]
- from the call-site (i.e. _dl_sort_maps(maps+1,nmaps-1)) is in general
- no longer valid, since traversing along object dependency-links
- may "find" the main object even when it is not included in the initial
- order (e.g. a dlopen()'ed shared object can have circular dependencies
- linked back to itself). In such a case, traversing N-1 objects will
- create a N-object result, and raise problems.
-
To summarize, just passing in the full list, and iterating from back
to front makes things much more straightforward. */
@@ -274,6 +267,27 @@ _dl_sort_maps_dfs (struct link_map **maps, unsigned int nmaps,
}
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
+ first object even when it is not included in the initial order
+ (e.g., a dlopen'ed shared object can have circular dependencies
+ linked back to itself). In such a case, traversing N-1 objects
+ will create a N-object result, and raise problems. Instead,
+ force the object back into first place after sorting. This naive
+ approach may introduce further dependency ordering violations
+ compared to rotating the cycle until the first map is again in
+ the first position, but as there is a cycle, at least one
+ violation is already present. */
+ if (force_first && maps[0] != first_map)
+ {
+ int i;
+ for (i = 0; maps[i] != first_map; ++i)
+ ;
+ assert (i < nmaps);
+ memmove (&maps[1], maps, i * sizeof (maps[0]));
+ maps[0] = first_map;
+ }
}
void
diff --git a/elf/dso-sort-tests-1.def b/elf/dso-sort-tests-1.def
index 5f7f18ef270bc12d..4bf9052db16fb352 100644
--- a/elf/dso-sort-tests-1.def
+++ b/elf/dso-sort-tests-1.def
@@ -64,3 +64,10 @@ output: b>a>{}<a<b
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];}
+
+# Test that even in the presence of dependency loops involving dlopen'ed
+# object, that object is initialized last (and not unloaded prematurely).
+# Final destructor order is indeterminate due to the cycle.
+tst-bz28937: {+a;+b;-b;+c;%c};a->a1;a->a2;a2->a;b->b1;c->a1;c=>a1
+output(glibc.rtld.dynamic_sort=1): {+a[a2>a1>a>];+b[b1>b>];-b[<b<b1];+c[c>];%c(a1());}<a<a2<c<a1
+output(glibc.rtld.dynamic_sort=2): {+a[a2>a1>a>];+b[b1>b>];-b[<b<b1];+c[c>];%c(a1());}<a2<a<c<a1

8
glibc.spec
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@ -148,7 +148,7 @@ end \
Summary: The GNU libc libraries
Name: glibc
Version: %{glibcversion}
Release: 45%{?dist}
Release: 46%{?dist}
# In general, GPLv2+ is used by programs, LGPLv2+ is used for
# libraries.
@ -586,6 +586,9 @@ Patch378: glibc-upstream-2.34-306.patch
Patch379: glibc-upstream-2.34-307.patch
Patch380: glibc-upstream-2.34-308.patch
Patch381: glibc-rh2118666.patch
Patch382: glibc-rh2128615-1.patch
Patch383: glibc-rh2128615-2.patch
Patch384: glibc-rh2128615-3.patch
##############################################################################
# Continued list of core "glibc" package information:
@ -2642,6 +2645,9 @@ fi
%files -f compat-libpthread-nonshared.filelist -n compat-libpthread-nonshared
%changelog
* Tue Oct 11 2022 Florian Weimer <fweimer@redhat.com> - 2.34-46
- DSO dependency sort must put new map first even if in cycle (#2128615)
* Tue Oct 11 2022 Florian Weimer <fweimer@redhat.com> - 2.34-45
- Run tst-audit-tlsdesc{,-dlopen} on all architectures (#2118666)