Fix TLS corruption during dlopen()/dlclose() sequences (RHEL-17465)
Resolves: RHEL-17465
This commit is contained in:
Carlos O'Donell
parent
46256b791c
commit
806a394144
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@ -0,0 +1,47 @@
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commit 3921c5b40f293c57cb326f58713c924b0662ef59
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Author: Hector Martin <marcan@marcan.st>
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Date: Tue Nov 28 15:23:07 2023 +0900
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elf: Fix TLS modid reuse generation assignment (BZ 29039)
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_dl_assign_tls_modid() assigns a slotinfo entry for a new module, but
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does *not* do anything to the generation counter. The first time this
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happens, the generation is zero and map_generation() returns the current
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generation to be used during relocation processing. However, if
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a slotinfo entry is later reused, it will already have a generation
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assigned. If this generation has fallen behind the current global max
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generation, then this causes an obsolete generation to be assigned
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during relocation processing, as map_generation() returns this
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generation if nonzero. _dl_add_to_slotinfo() eventually resets the
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generation, but by then it is too late. This causes DTV updates to be
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skipped, leading to NULL or broken TLS slot pointers and segfaults.
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Fix this by resetting the generation to zero in _dl_assign_tls_modid(),
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so it behaves the same as the first time a slot is assigned.
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_dl_add_to_slotinfo() will still assign the correct static generation
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later during module load, but relocation processing will no longer use
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an obsolete generation.
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Note that slotinfo entry (aka modid) reuse typically happens after a
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dlclose and only TLS access via dynamic tlsdesc is affected. Because
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tlsdesc is optimized to use the optional part of static TLS, dynamic
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tlsdesc can be avoided by increasing the glibc.rtld.optional_static_tls
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tunable to a large enough value, or by LD_PRELOAD-ing the affected
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modules.
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Fixes bug 29039.
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Reviewed-by: Szabolcs Nagy <szabolcs.nagy@arm.com>
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diff --git a/elf/dl-tls.c b/elf/dl-tls.c
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index b8ada16f1637c910..b9dc56e81a3b43db 100644
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--- a/elf/dl-tls.c
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+++ b/elf/dl-tls.c
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@@ -160,6 +160,7 @@ _dl_assign_tls_modid (struct link_map *l)
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{
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/* Mark the entry as used, so any dependency see it. */
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atomic_store_relaxed (&runp->slotinfo[result - disp].map, l);
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+ atomic_store_relaxed (&runp->slotinfo[result - disp].gen, 0);
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break;
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}
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@ -0,0 +1,198 @@
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commit 980450f12685326729d63ff72e93a996113bf073
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Author: Szabolcs Nagy <szabolcs.nagy@arm.com>
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Date: Wed Nov 29 11:31:37 2023 +0000
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elf: Add TLS modid reuse test for bug 29039
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This is a minimal regression test for bug 29039 which only affects
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targets with TLSDESC and a reproducer requires that
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1) Have modid gaps (closed modules) with old generation.
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2) Update a DTV to a newer generation (needs a newer dlopen).
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3) But do not update the closed gap entry in that DTV.
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4) Reuse the modid gap for a new module (another dlopen).
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5) Use dynamic TLSDESC in that new module with old generation (bug).
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6) Access TLS via this TLSDESC and the now outdated DTV.
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However step (3) in practice rarely happens: during DTV update the
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entries for closed modids are initialized to "unallocated" and then
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dynamic TLSDESC calls __tls_get_addr independently of its generation.
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The only exception to this is DTV setup at thread creation (gaps are
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initialized to NULL instead of unallocated) or DTV resize where the
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gap entries are outside the previous DTV array (again NULL instead
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of unallocated, and this requires loading > DTV_SURPLUS modules).
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So the bug can only cause NULL (+ offset) dereference, not use after
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free. And the easiest way to get (3) is via thread creation.
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Note that step (5) requires that the newly loaded module has larger
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TLS than the remaining optional static TLS. And for (6) there cannot
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be other TLS access or dlopen in the thread that updates the DTV.
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Tested on aarch64-linux-gnu.
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Reviewed-by: Adhemerval Zanella <adhemerval.zanella@linaro.org>
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Conflicts:
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elf/Makefile
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(Resolve test case ordering conflict.)
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diff --git a/elf/Makefile b/elf/Makefile
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index 7b7c6c171ce23247..7d55e68a55b54bd6 100644
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--- a/elf/Makefile
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+++ b/elf/Makefile
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@@ -447,6 +447,7 @@ tests += \
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tst-tls5 \
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tst-tlsalign \
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tst-tlsalign-extern \
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+ tst-tlsgap \
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tst-tls-dlinfo \
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tst-tls-ie \
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tst-tls-ie-dlmopen \
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@@ -798,6 +799,9 @@ modules-names = \
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tst-tls20mod-bad \
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tst-tls21mod \
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tst-tlsalign-lib \
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+ tst-tlsgap-mod0 \
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+ tst-tlsgap-mod1 \
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+ tst-tlsgap-mod2 \
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tst-tls-ie-mod0 \
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tst-tls-ie-mod1 \
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tst-tls-ie-mod2 \
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@@ -2710,3 +2714,14 @@ $(objpfx)tst-nodeps2-mod.so: $(common-objpfx)libc.so \
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$(LINK.o) -Wl,--no-as-needed -nostartfiles -nostdlib -shared -o $@ $^
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$(objpfx)tst-nodeps2.out: \
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$(objpfx)tst-nodeps1-mod.so $(objpfx)tst-nodeps2-mod.so
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+
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+$(objpfx)tst-tlsgap: $(shared-thread-library)
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+$(objpfx)tst-tlsgap.out: \
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+ $(objpfx)tst-tlsgap-mod0.so \
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+ $(objpfx)tst-tlsgap-mod1.so \
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+ $(objpfx)tst-tlsgap-mod2.so
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+ifeq (yes,$(have-mtls-dialect-gnu2))
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+CFLAGS-tst-tlsgap-mod0.c += -mtls-dialect=gnu2
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+CFLAGS-tst-tlsgap-mod1.c += -mtls-dialect=gnu2
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+CFLAGS-tst-tlsgap-mod2.c += -mtls-dialect=gnu2
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+endif
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diff --git a/elf/tst-tlsgap-mod0.c b/elf/tst-tlsgap-mod0.c
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new file mode 100644
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index 0000000000000000..1478b0beac5faf98
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--- /dev/null
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+++ b/elf/tst-tlsgap-mod0.c
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@@ -0,0 +1,2 @@
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+int __thread tls0;
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+int *f0(void) { return &tls0; }
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diff --git a/elf/tst-tlsgap-mod1.c b/elf/tst-tlsgap-mod1.c
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new file mode 100644
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index 0000000000000000..b10fc3702c43e478
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--- /dev/null
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+++ b/elf/tst-tlsgap-mod1.c
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@@ -0,0 +1,2 @@
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+int __thread tls1[100]; /* Size > glibc.rtld.optional_static_tls / 2. */
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+int *f1(void) { return tls1; }
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diff --git a/elf/tst-tlsgap-mod2.c b/elf/tst-tlsgap-mod2.c
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new file mode 100644
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index 0000000000000000..166c27d7f3fac252
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--- /dev/null
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+++ b/elf/tst-tlsgap-mod2.c
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@@ -0,0 +1,2 @@
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+int __thread tls2;
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+int *f2(void) { return &tls2; }
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diff --git a/elf/tst-tlsgap.c b/elf/tst-tlsgap.c
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new file mode 100644
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index 0000000000000000..49328850769c5609
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--- /dev/null
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+++ b/elf/tst-tlsgap.c
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@@ -0,0 +1,92 @@
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+/* TLS modid gap reuse regression test for bug 29039.
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+ Copyright (C) 2023 Free Software Foundation, Inc.
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+ This file is part of the GNU C Library.
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+
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+ The GNU C Library is free software; you can redistribute it and/or
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+ modify it under the terms of the GNU Lesser General Public
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+ License as published by the Free Software Foundation; either
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+ version 2.1 of the License, or (at your option) any later version.
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+
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+ The GNU C Library is distributed in the hope that it will be useful,
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+ but WITHOUT ANY WARRANTY; without even the implied warranty of
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+ MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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+ Lesser General Public License for more details.
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+
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+ You should have received a copy of the GNU Lesser General Public
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+ License along with the GNU C Library; if not, see
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+ <http://www.gnu.org/licenses/>. */
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+
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+#include <stdio.h>
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+#include <dlfcn.h>
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+#include <pthread.h>
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+#include <support/xdlfcn.h>
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+#include <support/xthread.h>
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+#include <support/check.h>
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+
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+static void *mod[3];
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+#define MOD(i) "tst-tlsgap-mod" #i ".so"
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+static const char *modname[3] = { MOD(0), MOD(1), MOD(2) };
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+#undef MOD
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+
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+static void
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+open_mod (int i)
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+{
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+ mod[i] = xdlopen (modname[i], RTLD_LAZY);
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+ printf ("open %s\n", modname[i]);
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+}
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+
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+static void
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+close_mod (int i)
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+{
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+ xdlclose (mod[i]);
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+ mod[i] = NULL;
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+ printf ("close %s\n", modname[i]);
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+}
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+
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+static void
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+access_mod (int i, const char *sym)
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+{
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+ int *(*f) (void) = xdlsym (mod[i], sym);
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+ int *p = f ();
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+ printf ("access %s: %s() = %p\n", modname[i], sym, p);
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+ TEST_VERIFY_EXIT (p != NULL);
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+ ++*p;
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+}
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+
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+static void *
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+start (void *arg)
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+{
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+ /* The DTV generation is at the last dlopen of mod0 and the
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+ entry for mod1 is NULL. */
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+
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+ open_mod (1); /* Reuse modid of mod1. Uses dynamic TLS. */
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+
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+ /* DTV is unchanged: dlopen only updates the DTV to the latest
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+ generation if static TLS is allocated for a loaded module.
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+
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+ With bug 29039, the TLSDESC relocation in mod1 uses the old
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+ dlclose generation of mod1 instead of the new dlopen one so
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+ DTV is not updated on TLS access. */
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+
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+ access_mod (1, "f1");
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+
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+ return arg;
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+}
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+
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+static int
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+do_test (void)
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+{
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+ open_mod (0);
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+ open_mod (1);
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+ open_mod (2);
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+ close_mod (0);
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+ close_mod (1); /* Create modid gap at mod1. */
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+ open_mod (0); /* Reuse modid of mod0, bump generation count. */
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+
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+ /* Create a thread where DTV of mod1 is NULL. */
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+ pthread_t t = xpthread_create (NULL, start, NULL);
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+ xpthread_join (t);
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+ return 0;
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+}
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+
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+#include <support/test-driver.c>
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@ -155,7 +155,7 @@ end \
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Summary: The GNU libc libraries
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Name: glibc
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Version: %{glibcversion}
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Release: 95%{?dist}
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Release: 96%{?dist}
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# In general, GPLv2+ is used by programs, LGPLv2+ is used for
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# libraries.
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@ -797,6 +797,8 @@ Patch560: glibc-RHEL-17319-1.patch
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Patch561: glibc-RHEL-17319-2.patch
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Patch562: glibc-RHEL-17319-3.patch
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Patch563: glibc-RHEL-17319-4.patch
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Patch564: glibc-RHEL-17465-1.patch
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Patch565: glibc-RHEL-17465-2.patch
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##############################################################################
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# Continued list of core "glibc" package information:
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@ -2955,6 +2957,9 @@ update_gconv_modules_cache ()
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%endif
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%changelog
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* Thu Dec 21 2023 Carlos O'Donell <carlos@redhat.com> - 2.34-96
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- Fix TLS corruption during dlopen()/dlclose() sequences (RHEL-17465)
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* Fri Dec 8 2023 Florian Weimer <fweimer@redhat.com> - 2.34-95
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- Improve compatibility between underlinking and IFUNC resolvers (RHEL-17319)
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