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Upstream patches for fallout from dlopen NODELETE changes (#1778344, #1778366)

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Florian Weimer 2019-12-05 17:38:17 +01:00
parent 134ad59d86
commit e9451d9caf
4 changed files with 1659 additions and 2 deletions
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1226
glibc-dlopen-nodelete-fixes-1.patch Normal file
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296
glibc-dlopen-nodelete-fixes-2.patch Normal file
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@ -0,0 +1,296 @@
Author: Florian Weimer <fweimer@redhat.com>
Date: Thu Dec 5 13:32:42 2019 +0100
dlopen: Rework handling of pending NODELETE status
To avoid a read-modify-write cycle on the l_nodelete field, this
commit introduces two flags for active NODELETE status (irrevocable)
and pending NODELETE status (revocable until activate_nodelete) is
invoked. As a result, NODELETE processing in dlopen does not
introduce further reasons why lazy binding from signal handlers
is unsafe during dlopen, and a subsequent commit can remove signal
blocking from dlopen.
diff --git a/elf/dl-close.c b/elf/dl-close.c
index e35a62daf6fa98a1..df1df6fb298b2319 100644
--- a/elf/dl-close.c
+++ b/elf/dl-close.c
@@ -197,7 +197,7 @@ _dl_close_worker (struct link_map *map, bool force)
/* Check whether this object is still used. */
if (l->l_type == lt_loaded
&& l->l_direct_opencount == 0
- && l->l_nodelete != link_map_nodelete_active
+ && !l->l_nodelete_active
/* See CONCURRENCY NOTES in cxa_thread_atexit_impl.c to know why
acquire is sufficient and correct. */
&& atomic_load_acquire (&l->l_tls_dtor_count) == 0
@@ -279,8 +279,7 @@ _dl_close_worker (struct link_map *map, bool force)
if (!used[i])
{
- assert (imap->l_type == lt_loaded
- && imap->l_nodelete != link_map_nodelete_active);
+ assert (imap->l_type == lt_loaded && !imap->l_nodelete_active);
/* Call its termination function. Do not do it for
half-cooked objects. Temporarily disable exception
@@ -830,7 +829,7 @@ _dl_close (void *_map)
before we took the lock. There is no way to detect this (see below)
so we proceed assuming this isn't the case. First see whether we
can remove the object at all. */
- if (__glibc_unlikely (map->l_nodelete == link_map_nodelete_active))
+ if (__glibc_unlikely (map->l_nodelete_active))
{
/* Nope. Do nothing. */
__rtld_lock_unlock_recursive (GL(dl_load_lock));
diff --git a/elf/dl-lookup.c b/elf/dl-lookup.c
index 99846918c3453694..759b45a2c977175a 100644
--- a/elf/dl-lookup.c
+++ b/elf/dl-lookup.c
@@ -187,6 +187,28 @@ enter_unique_sym (struct unique_sym *table, size_t size,
table[idx].map = map;
}
+/* Mark MAP as NODELETE according to the lookup mode in FLAGS. During
+ initial relocation, NODELETE state is pending only. */
+static void
+mark_nodelete (struct link_map *map, int flags)
+{
+ if (flags & DL_LOOKUP_FOR_RELOCATE)
+ map->l_nodelete_pending = true;
+ else
+ map->l_nodelete_active = true;
+}
+
+/* Return true if MAP is marked as NODELETE according to the lookup
+ mode in FLAGS> */
+static bool
+is_nodelete (struct link_map *map, int flags)
+{
+ /* Non-pending NODELETE always counts. Pending NODELETE only counts
+ during initial relocation processing. */
+ return map->l_nodelete_active
+ || ((flags & DL_LOOKUP_FOR_RELOCATE) && map->l_nodelete_pending);
+}
+
/* Utility function for do_lookup_x. Lookup an STB_GNU_UNIQUE symbol
in the unique symbol table, creating a new entry if necessary.
Return the matching symbol in RESULT. */
@@ -311,8 +333,7 @@ do_lookup_unique (const char *undef_name, uint_fast32_t new_hash,
enter_unique_sym (entries, size,
new_hash, strtab + sym->st_name, sym, map);
- if (map->l_type == lt_loaded
- && map->l_nodelete == link_map_nodelete_inactive)
+ if (map->l_type == lt_loaded && !is_nodelete (map, flags))
{
/* Make sure we don't unload this object by
setting the appropriate flag. */
@@ -320,10 +341,7 @@ do_lookup_unique (const char *undef_name, uint_fast32_t new_hash,
_dl_debug_printf ("\
marking %s [%lu] as NODELETE due to unique symbol\n",
map->l_name, map->l_ns);
- if (flags & DL_LOOKUP_FOR_RELOCATE)
- map->l_nodelete = link_map_nodelete_pending;
- else
- map->l_nodelete = link_map_nodelete_active;
+ mark_nodelete (map, flags);
}
}
++tab->n_elements;
@@ -586,7 +604,7 @@ add_dependency (struct link_map *undef_map, struct link_map *map, int flags)
dependencies may pick an dependency which can be dlclose'd, but
such IFUNC resolvers are undefined anyway. */
assert (map->l_type == lt_loaded);
- if (map->l_nodelete != link_map_nodelete_inactive)
+ if (is_nodelete (map, flags))
return 0;
struct link_map_reldeps *l_reldeps
@@ -694,17 +712,16 @@ add_dependency (struct link_map *undef_map, struct link_map *map, int flags)
/* Redo the NODELETE check, as when dl_load_lock wasn't held
yet this could have changed. */
- if (map->l_nodelete != link_map_nodelete_inactive)
+ if (is_nodelete (map, flags))
goto out;
/* If the object with the undefined reference cannot be removed ever
just make sure the same is true for the object which contains the
definition. */
- if (undef_map->l_type != lt_loaded
- || (undef_map->l_nodelete != link_map_nodelete_inactive))
+ if (undef_map->l_type != lt_loaded || is_nodelete (map, flags))
{
if (__glibc_unlikely (GLRO (dl_debug_mask) & DL_DEBUG_BINDINGS)
- && map->l_nodelete == link_map_nodelete_inactive)
+ && !is_nodelete (map, flags))
{
if (undef_map->l_name[0] == '\0')
_dl_debug_printf ("\
@@ -716,11 +733,7 @@ marking %s [%lu] as NODELETE due to reference to %s [%lu]\n",
map->l_name, map->l_ns,
undef_map->l_name, undef_map->l_ns);
}
-
- if (flags & DL_LOOKUP_FOR_RELOCATE)
- map->l_nodelete = link_map_nodelete_pending;
- else
- map->l_nodelete = link_map_nodelete_active;
+ mark_nodelete (map, flags);
goto out;
}
@@ -746,17 +759,14 @@ marking %s [%lu] as NODELETE due to reference to %s [%lu]\n",
cannot be unloaded. This is semantically the correct
behavior. */
if (__glibc_unlikely (GLRO (dl_debug_mask) & DL_DEBUG_BINDINGS)
- && map->l_nodelete == link_map_nodelete_inactive)
+ && !is_nodelete (map, flags))
_dl_debug_printf ("\
marking %s [%lu] as NODELETE due to memory allocation failure\n",
map->l_name, map->l_ns);
- if (flags & DL_LOOKUP_FOR_RELOCATE)
- /* In case of non-lazy binding, we could actually
- report the memory allocation error, but for now, we
- use the conservative approximation as well. */
- map->l_nodelete = link_map_nodelete_pending;
- else
- map->l_nodelete = link_map_nodelete_active;
+ /* In case of non-lazy binding, we could actually report
+ the memory allocation error, but for now, we use the
+ conservative approximation as well. */
+ mark_nodelete (map, flags);
goto out;
}
else
diff --git a/elf/dl-open.c b/elf/dl-open.c
index 56f213323ce5cf65..c23341be5892fb12 100644
--- a/elf/dl-open.c
+++ b/elf/dl-open.c
@@ -440,13 +440,17 @@ activate_nodelete (struct link_map *new)
NODELETE status for objects outside the local scope. */
for (struct link_map *l = GL (dl_ns)[new->l_ns]._ns_loaded; l != NULL;
l = l->l_next)
- if (l->l_nodelete == link_map_nodelete_pending)
+ if (l->l_nodelete_pending)
{
if (__glibc_unlikely (GLRO (dl_debug_mask) & DL_DEBUG_FILES))
_dl_debug_printf ("activating NODELETE for %s [%lu]\n",
l->l_name, l->l_ns);
- l->l_nodelete = link_map_nodelete_active;
+ l->l_nodelete_active = true;
+
+ /* This is just a debugging aid, to indicate that
+ activate_nodelete has run for this map. */
+ l->l_nodelete_pending = false;
}
}
@@ -549,10 +553,10 @@ dl_open_worker (void *a)
if (__glibc_unlikely (mode & RTLD_NODELETE))
{
if (__glibc_unlikely (GLRO (dl_debug_mask) & DL_DEBUG_FILES)
- && new->l_nodelete == link_map_nodelete_inactive)
+ && !new->l_nodelete_active)
_dl_debug_printf ("marking %s [%lu] as NODELETE\n",
new->l_name, new->l_ns);
- new->l_nodelete = link_map_nodelete_active;
+ new->l_nodelete_active = true;
}
/* Finalize the addition to the global scope. */
@@ -568,7 +572,7 @@ dl_open_worker (void *a)
/* Schedule NODELETE marking for the directly loaded object if
requested. */
if (__glibc_unlikely (mode & RTLD_NODELETE))
- new->l_nodelete = link_map_nodelete_pending;
+ new->l_nodelete_pending = true;
/* Load that object's dependencies. */
_dl_map_object_deps (new, NULL, 0, 0,
@@ -683,7 +687,7 @@ dl_open_worker (void *a)
_dl_start_profile ();
/* Prevent unloading the object. */
- GL(dl_profile_map)->l_nodelete = link_map_nodelete_active;
+ GL(dl_profile_map)->l_nodelete_active = true;
}
}
else
@@ -882,9 +886,9 @@ no more namespaces available for dlmopen()"));
happens inside dl_open_worker. */
__libc_signal_restore_set (&args.original_signal_mask);
- /* All link_map_nodelete_pending objects should have been
- deleted at this point, which is why it is not necessary
- to reset the flag here. */
+ /* All l_nodelete_pending objects should have been deleted
+ at this point, which is why it is not necessary to reset
+ the flag here. */
}
else
__libc_signal_restore_set (&args.original_signal_mask);
diff --git a/elf/get-dynamic-info.h b/elf/get-dynamic-info.h
index 075683d729447a40..ea4e304bef282a6f 100644
--- a/elf/get-dynamic-info.h
+++ b/elf/get-dynamic-info.h
@@ -164,7 +164,7 @@ elf_get_dynamic_info (struct link_map *l, ElfW(Dyn) *temp)
{
l->l_flags_1 = info[VERSYMIDX (DT_FLAGS_1)]->d_un.d_val;
if (l->l_flags_1 & DF_1_NODELETE)
- l->l_nodelete = link_map_nodelete_pending;
+ l->l_nodelete_pending = true;
/* Only DT_1_SUPPORTED_MASK bits are supported, and we would like
to assert this, but we can't. Users have been setting
diff --git a/include/link.h b/include/link.h
index 2e771e433a36e6cd..2acc8363802d6d64 100644
--- a/include/link.h
+++ b/include/link.h
@@ -79,22 +79,6 @@ struct r_search_path_struct
int malloced;
};
-/* Type used by the l_nodelete member. */
-enum link_map_nodelete
-{
- /* This link map can be deallocated. */
- link_map_nodelete_inactive = 0, /* Zero-initialized in _dl_new_object. */
-
- /* This link map cannot be deallocated. */
- link_map_nodelete_active,
-
- /* This link map cannot be deallocated after dlopen has succeded.
- dlopen turns this into link_map_nodelete_active. dlclose treats
- this intermediate state as link_map_nodelete_active. */
- link_map_nodelete_pending,
-};
-
-
/* Structure describing a loaded shared object. The `l_next' and `l_prev'
members form a chain of all the shared objects loaded at startup.
@@ -218,10 +202,17 @@ struct link_map
freed, ie. not allocated with
the dummy malloc in ld.so. */
- /* Actually of type enum link_map_nodelete. Separate byte due to
- a read in add_dependency in elf/dl-lookup.c outside the loader
- lock. Only valid for l_type == lt_loaded. */
- unsigned char l_nodelete;
+ /* NODELETE status of the map. Only valid for maps of type
+ lt_loaded. Lazy binding sets l_nodelete_active directly,
+ potentially from signal handlers. Initial loading of an
+ DF_1_NODELETE object set l_nodelete_pending. Relocation may
+ set l_nodelete_pending as well. l_nodelete_pending maps are
+ promoted to l_nodelete_active status in the final stages of
+ dlopen, prior to calling ELF constructors. dlclose only
+ refuses to unload l_nodelete_active maps, the pending status is
+ ignored. */
+ bool l_nodelete_active;
+ bool l_nodelete_pending;
#include <link_map.h>

130
glibc-dlopen-nodelete-fixes-3.patch Normal file
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@ -0,0 +1,130 @@
Author: Florian Weimer <fweimer@redhat.com>
Date: Thu Dec 5 16:20:30 2019 +0100
dlopen: Do not block signals
Blocking signals causes issues with certain anti-malware solutions
which rely on an unblocked SIGSYS signal for system calls they
intercept.
This reverts commit a2e8aa0d9ea648068d8be52dd7b15f1b6a008e23
("Block signals during the initial part of dlopen") and adds
comments related to async signal safety to active_nodelete and
its caller.
Note that this does not make lazy binding async-signal-safe with regards
to dlopen. It merely avoids introducing new async-signal-safety hazards
as part of the NODELETE changes.
diff --git a/elf/dl-open.c b/elf/dl-open.c
index c23341be5892fb12..5a1c5b53269f1236 100644
--- a/elf/dl-open.c
+++ b/elf/dl-open.c
@@ -34,7 +34,6 @@
#include <atomic.h>
#include <libc-internal.h>
#include <array_length.h>
-#include <internal-signals.h>
#include <dl-dst.h>
#include <dl-prop.h>
@@ -53,10 +52,6 @@ struct dl_open_args
/* Namespace ID. */
Lmid_t nsid;
- /* Original signal mask. Used for unblocking signal handlers before
- running ELF constructors. */
- sigset_t original_signal_mask;
-
/* Original value of _ns_global_scope_pending_adds. Set by
dl_open_worker. Only valid if nsid is a real namespace
(non-negative). */
@@ -446,6 +441,9 @@ activate_nodelete (struct link_map *new)
_dl_debug_printf ("activating NODELETE for %s [%lu]\n",
l->l_name, l->l_ns);
+ /* The flag can already be true at this point, e.g. a signal
+ handler may have triggered lazy binding and set NODELETE
+ status immediately. */
l->l_nodelete_active = true;
/* This is just a debugging aid, to indicate that
@@ -520,16 +518,12 @@ dl_open_worker (void *a)
if (new == NULL)
{
assert (mode & RTLD_NOLOAD);
- __libc_signal_restore_set (&args->original_signal_mask);
return;
}
if (__glibc_unlikely (mode & __RTLD_SPROF))
- {
- /* This happens only if we load a DSO for 'sprof'. */
- __libc_signal_restore_set (&args->original_signal_mask);
- return;
- }
+ /* This happens only if we load a DSO for 'sprof'. */
+ return;
/* This object is directly loaded. */
++new->l_direct_opencount;
@@ -565,7 +559,6 @@ dl_open_worker (void *a)
assert (_dl_debug_initialize (0, args->nsid)->r_state == RT_CONSISTENT);
- __libc_signal_restore_set (&args->original_signal_mask);
return;
}
@@ -712,6 +705,12 @@ dl_open_worker (void *a)
All memory allocations for new objects must have happened
before. */
+ /* Finalize the NODELETE status first. This comes before
+ update_scopes, so that lazy binding will not see pending NODELETE
+ state for newly loaded objects. There is a compiler barrier in
+ update_scopes which ensures that the changes from
+ activate_nodelete are visible before new objects show up in the
+ local scope. */
activate_nodelete (new);
/* Second stage after resize_scopes: Actually perform the scope
@@ -745,10 +744,6 @@ dl_open_worker (void *a)
if (mode & RTLD_GLOBAL)
add_to_global_resize (new);
- /* Unblock signals. Data structures are now consistent, and
- application code may run. */
- __libc_signal_restore_set (&args->original_signal_mask);
-
/* Run the initializer functions of new objects. Temporarily
disable the exception handler, so that lazy binding failures are
fatal. */
@@ -838,10 +833,6 @@ no more namespaces available for dlmopen()"));
args.argv = argv;
args.env = env;
- /* Recursive lazy binding during manipulation of the dynamic loader
- structures may result in incorrect behavior. */
- __libc_signal_block_all (&args.original_signal_mask);
-
struct dl_exception exception;
int errcode = _dl_catch_exception (&exception, dl_open_worker, &args);
@@ -882,16 +873,10 @@ no more namespaces available for dlmopen()"));
_dl_close_worker (args.map, true);
- /* Restore the signal mask. In the success case, this
- happens inside dl_open_worker. */
- __libc_signal_restore_set (&args.original_signal_mask);
-
/* All l_nodelete_pending objects should have been deleted
at this point, which is why it is not necessary to reset
the flag here. */
}
- else
- __libc_signal_restore_set (&args.original_signal_mask);
assert (_dl_debug_initialize (0, args.nsid)->r_state == RT_CONSISTENT);

9
glibc.spec
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@ -87,7 +87,7 @@
Summary: The GNU libc libraries
Name: glibc
Version: %{glibcversion}
Release: 23%{?dist}
Release: 24%{?dist}
# In general, GPLv2+ is used by programs, LGPLv2+ is used for
# libraries.
@ -158,7 +158,9 @@ Patch17: glibc-cs-path.patch
Patch18: glibc-c-utf8-locale.patch
Patch23: glibc-python3.patch
Patch29: glibc-fedora-nsswitch.patch
Patch30: glibc-rh1778344.patch
Patch30: glibc-dlopen-nodelete-fixes-1.patch
Patch31: glibc-dlopen-nodelete-fixes-2.patch
Patch32: glibc-dlopen-nodelete-fixes-3.patch
##############################################################################
# Continued list of core "glibc" package information:
@ -2042,6 +2044,9 @@ fi
%files -f compat-libpthread-nonshared.filelist -n compat-libpthread-nonshared
%changelog
* Thu Dec 5 2019 Florian Weimer <fweimer@redhat.com> - 2.30.9000-24
- Upstream patches for fallout from dlopen NODELETE changes (#1778344, #1778366)
* Wed Dec 04 2019 Patsy Franklin <patsy@redhat.com> - 2.30.9000-23
- Auto-sync with upstream branch master,
commit ec138c67cbda8b5826a0a2a7ba456408117996dc.