192 lines
7.0 KiB
Diff
192 lines
7.0 KiB
Diff
commit bde121872001d8f3224eeafa5b7effb871c3fbca
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Author: Simon Kissane <skissane@gmail.com>
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Date: Sat Feb 11 08:58:02 2023 +1100
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gmon: fix memory corruption issues [BZ# 30101]
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V2 of this patch fixes an issue in V1, where the state was changed to ON not
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OFF at end of _mcleanup. I hadn't noticed that (counterintuitively) ON=0 and
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OFF=3, hence zeroing the buffer turned it back on. So set the state to OFF
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after the memset.
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1. Prevent double free, and reads from unallocated memory, when
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_mcleanup is (incorrectly) called two or more times in a row,
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without an intervening call to __monstartup; with this patch, the
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second and subsequent calls effectively become no-ops instead.
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While setting tos=NULL is minimal fix, safest action is to zero the
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whole gmonparam buffer.
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2. Prevent memory leak when __monstartup is (incorrectly) called two
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or more times in a row, without an intervening call to _mcleanup;
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with this patch, the second and subsequent calls effectively become
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no-ops instead.
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3. After _mcleanup, treat __moncontrol(1) as __moncontrol(0) instead.
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With zeroing of gmonparam buffer in _mcleanup, this stops the
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state incorrectly being changed to GMON_PROF_ON despite profiling
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actually being off. If we'd just done the minimal fix to _mcleanup
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of setting tos=NULL, there is risk of far worse memory corruption:
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kcount would point to deallocated memory, and the __profil syscall
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would make the kernel write profiling data into that memory,
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which could have since been reallocated to something unrelated.
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4. Ensure __moncontrol(0) still turns off profiling even in error
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state. Otherwise, if mcount overflows and sets state to
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GMON_PROF_ERROR, when _mcleanup calls __moncontrol(0), the __profil
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syscall to disable profiling will not be invoked. _mcleanup will
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free the buffer, but the kernel will still be writing profiling
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data into it, potentially corrupted arbitrary memory.
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Also adds a test case for (1). Issues (2)-(4) are not feasible to test.
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Signed-off-by: Simon Kissane <skissane@gmail.com>
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Reviewed-by: DJ Delorie <dj@redhat.com>
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Conflicts:
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gmon/Makefile
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(copyright year update)
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diff --git a/gmon/Makefile b/gmon/Makefile
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index 54f05894d4dd8c4a..1bc4ad6e14e292a9 100644
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--- a/gmon/Makefile
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+++ b/gmon/Makefile
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@@ -1,4 +1,5 @@
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-# Copyright (C) 1995-2018 Free Software Foundation, Inc.
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+# Copyright (C) 1995-2023 Free Software Foundation, Inc.
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+# Copyright The GNU Toolchain Authors.
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# This file is part of the GNU C Library.
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# The GNU C Library is free software; you can redistribute it and/or
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@@ -25,7 +26,7 @@ include ../Makeconfig
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headers := sys/gmon.h sys/gmon_out.h sys/profil.h
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routines := gmon mcount profil sprofil prof-freq
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-tests = tst-sprofil tst-gmon tst-mcount-overflow
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+tests = tst-sprofil tst-gmon tst-mcount-overflow tst-mcleanup
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ifeq ($(build-profile),yes)
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tests += tst-profile-static
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tests-static += tst-profile-static
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@@ -68,6 +69,14 @@ ifeq ($(run-built-tests),yes)
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tests-special += $(objpfx)tst-mcount-overflow-check.out
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endif
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+CFLAGS-tst-mcleanup.c := -fno-omit-frame-pointer -pg
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+tst-mcleanup-no-pie = yes
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+CRT-tst-mcleanup := $(csu-objpfx)g$(start-installed-name)
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+tst-mcleanup-ENV := GMON_OUT_PREFIX=$(objpfx)tst-mcleanup.data
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+ifeq ($(run-built-tests),yes)
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+tests-special += $(objpfx)tst-mcleanup.out
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+endif
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+
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CFLAGS-tst-gmon-static.c := $(PIE-ccflag) -fno-omit-frame-pointer -pg
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CRT-tst-gmon-static := $(csu-objpfx)gcrt1.o
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tst-gmon-static-no-pie = yes
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@@ -123,6 +132,10 @@ $(objpfx)tst-mcount-overflow-check.out: tst-mcount-overflow-check.sh $(objpfx)ts
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$(SHELL) $< $(objpfx)tst-mcount-overflow > $@; \
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$(evaluate-test)
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+$(objpfx)tst-mcleanup.out: clean-tst-mcleanup-data
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+clean-tst-mcleanup-data:
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+ rm -f $(objpfx)tst-mcleanup.data.*
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+
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$(objpfx)tst-gmon-gprof.out: tst-gmon-gprof.sh $(objpfx)tst-gmon.out
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$(SHELL) $< $(GPROF) $(objpfx)tst-gmon $(objpfx)tst-gmon.data.* > $@; \
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$(evaluate-test)
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diff --git a/gmon/gmon.c b/gmon/gmon.c
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index 689bf80141e559ca..5e99a7351dc71666 100644
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--- a/gmon/gmon.c
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+++ b/gmon/gmon.c
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@@ -102,11 +102,8 @@ __moncontrol (int mode)
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{
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struct gmonparam *p = &_gmonparam;
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- /* Don't change the state if we ran into an error. */
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- if (p->state == GMON_PROF_ERROR)
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- return;
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-
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- if (mode)
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+ /* Treat start request as stop if error or gmon not initialized. */
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+ if (mode && p->state != GMON_PROF_ERROR && p->tos != NULL)
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{
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/* start */
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__profil((void *) p->kcount, p->kcountsize, p->lowpc, s_scale);
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@@ -116,7 +113,9 @@ __moncontrol (int mode)
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{
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/* stop */
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__profil(NULL, 0, 0, 0);
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- p->state = GMON_PROF_OFF;
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+ /* Don't change the state if we ran into an error. */
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+ if (p->state != GMON_PROF_ERROR)
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+ p->state = GMON_PROF_OFF;
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}
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}
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libc_hidden_def (__moncontrol)
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@@ -146,6 +145,14 @@ __monstartup (u_long lowpc, u_long highpc)
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maxarcs = MAXARCS;
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#endif
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+ /*
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+ * If we are incorrectly called twice in a row (without an
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+ * intervening call to _mcleanup), ignore the second call to
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+ * prevent leaking memory.
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+ */
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+ if (p->tos != NULL)
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+ return;
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+
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/*
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* round lowpc and highpc to multiples of the density we're using
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* so the rest of the scaling (here and in gprof) stays in ints.
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@@ -463,9 +470,14 @@ _mcleanup (void)
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{
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__moncontrol (0);
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- if (_gmonparam.state != GMON_PROF_ERROR)
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+ if (_gmonparam.state != GMON_PROF_ERROR && _gmonparam.tos != NULL)
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write_gmon ();
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/* free the memory. */
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free (_gmonparam.tos);
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+
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+ /* reset buffer to initial state for safety */
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+ memset(&_gmonparam, 0, sizeof _gmonparam);
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+ /* somewhat confusingly, ON=0, OFF=3 */
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+ _gmonparam.state = GMON_PROF_OFF;
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}
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diff --git a/gmon/tst-mcleanup.c b/gmon/tst-mcleanup.c
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new file mode 100644
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index 0000000000000000..b259653ec833aca4
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--- /dev/null
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+++ b/gmon/tst-mcleanup.c
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@@ -0,0 +1,31 @@
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+/* Test program for repeated invocation of _mcleanup
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+ Copyright The GNU Toolchain Authors.
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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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+ <https://www.gnu.org/licenses/>. */
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+
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+/* Intentionally calls _mcleanup() twice: once manually, it will be
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+ called again as an atexit handler. This is incorrect use of the API,
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+ but the point of the test is to make sure we don't crash when the
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+ API is misused in this way. */
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+
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+#include <sys/gmon.h>
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+
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+int
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+main (void)
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+{
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+ _mcleanup();
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+ return 0;
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+}
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