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[2403:5807:276c:0:d31:80ef:dd25:48b4]) by smtp.googlemail.com with ESMTPSA id x2-20020a170902a38200b0019a60b7cc0esm3457258pla.248.2023.02.10.13.58.21 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 10 Feb 2023 13:58:23 -0800 (PST) To: libc-alpha@sourceware.org Cc: Simon Kissane Subject: [PATCH v2] gmon: fix memory corruption issues [BZ# 30101] Date: Sat, 11 Feb 2023 08:58:02 +1100 Message-Id: <20230210215802.3429937-1-skissane@gmail.com> X-Mailer: git-send-email 2.25.1 MIME-Version: 1.0 X-Spam-Status: No, score=-11.5 required=5.0 tests=BAYES_00, DKIM_SIGNED, DKIM_VALID, DKIM_VALID_AU, DKIM_VALID_EF, FREEMAIL_FROM, GIT_PATCH_0, KAM_SHORT, RCVD_IN_DNSWL_NONE, SPF_HELO_NONE, SPF_PASS, TXREP autolearn=ham autolearn_force=no version=3.4.6 X-Spam-Checker-Version: SpamAssassin 3.4.6 (2021-04-09) on server2.sourceware.org X-BeenThere: libc-alpha@sourceware.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Libc-alpha mailing list List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-Patchwork-Original-From: Simon Kissane via Libc-alpha From: Simon Kissane Reply-To: Simon Kissane Errors-To: libc-alpha-bounces+patchwork=sourceware.org@sourceware.org Sender: "Libc-alpha" V2 of this patch fixes an issue in V1, where the state was changed to ON not OFF at end of _mcleanup. I hadn't noticed that (counterintuitively) ON=0 and OFF=3, hence zeroing the buffer turned it back on. So set the state to OFF after the memset. 1. Prevent double free, and reads from unallocated memory, when _mcleanup is (incorrectly) called two or more times in a row, without an intervening call to __monstartup; with this patch, the second and subsequent calls effectively become no-ops instead. While setting tos=NULL is minimal fix, safest action is to zero the whole gmonparam buffer. 2. Prevent memory leak when __monstartup is (incorrectly) called two or more times in a row, without an intervening call to _mcleanup; with this patch, the second and subsequent calls effectively become no-ops instead. 3. After _mcleanup, treat __moncontrol(1) as __moncontrol(0) instead. With zeroing of gmonparam buffer in _mcleanup, this stops the state incorrectly being changed to GMON_PROF_ON despite profiling actually being off. If we'd just done the minimal fix to _mcleanup of setting tos=NULL, there is risk of far worse memory corruption: kcount would point to deallocated memory, and the __profil syscall would make the kernel write profiling data into that memory, which could have since been reallocated to something unrelated. 4. Ensure __moncontrol(0) still turns off profiling even in error state. Otherwise, if mcount overflows and sets state to GMON_PROF_ERROR, when _mcleanup calls __moncontrol(0), the __profil syscall to disable profiling will not be invoked. _mcleanup will free the buffer, but the kernel will still be writing profiling data into it, potentially corrupted arbitrary memory. Also adds a test case for (1). Issues (2)-(4) are not feasible to test. Signed-off-by: Simon Kissane Reviewed-by: DJ Delorie --- gmon/Makefile | 15 ++++++++++++++- gmon/gmon.c | 26 +++++++++++++++++++------- gmon/tst-mcleanup.c | 31 +++++++++++++++++++++++++++++++ 3 files changed, 64 insertions(+), 8 deletions(-) create mode 100644 gmon/tst-mcleanup.c diff --git a/gmon/Makefile b/gmon/Makefile index 4dd5adb80b..33eb5f4320 100644 --- a/gmon/Makefile +++ b/gmon/Makefile @@ -1,4 +1,5 @@ # Copyright (C) 1995-2023 Free Software Foundation, Inc. +# Copyright The GNU Toolchain Authors. # This file is part of the GNU C Library. # The GNU C Library is free software; you can redistribute it and/or @@ -25,7 +26,7 @@ include ../Makeconfig headers := sys/gmon.h sys/gmon_out.h sys/profil.h routines := gmon mcount profil sprofil prof-freq -tests = tst-sprofil tst-gmon +tests = tst-sprofil tst-gmon tst-mcleanup ifeq ($(build-profile),yes) tests += tst-profile-static tests-static += tst-profile-static @@ -56,6 +57,14 @@ ifeq ($(run-built-tests),yes) tests-special += $(objpfx)tst-gmon-gprof.out endif +CFLAGS-tst-mcleanup.c := -fno-omit-frame-pointer -pg +tst-mcleanup-no-pie = yes +CRT-tst-mcleanup := $(csu-objpfx)g$(start-installed-name) +tst-mcleanup-ENV := GMON_OUT_PREFIX=$(objpfx)tst-mcleanup.data +ifeq ($(run-built-tests),yes) +tests-special += $(objpfx)tst-mcleanup.out +endif + CFLAGS-tst-gmon-static.c := $(PIE-ccflag) -fno-omit-frame-pointer -pg CRT-tst-gmon-static := $(csu-objpfx)g$(static-start-installed-name) tst-gmon-static-no-pie = yes @@ -103,6 +112,10 @@ $(objpfx)tst-gmon.out: clean-tst-gmon-data clean-tst-gmon-data: rm -f $(objpfx)tst-gmon.data.* +$(objpfx)tst-mcleanup.out: clean-tst-mcleanup-data +clean-tst-mcleanup-data: + rm -f $(objpfx)tst-mcleanup.data.* + $(objpfx)tst-gmon-gprof.out: tst-gmon-gprof.sh $(objpfx)tst-gmon.out $(SHELL) $< $(GPROF) $(objpfx)tst-gmon $(objpfx)tst-gmon.data.* > $@; \ $(evaluate-test) diff --git a/gmon/gmon.c b/gmon/gmon.c index dee64803ad..9940743aba 100644 --- a/gmon/gmon.c +++ b/gmon/gmon.c @@ -97,11 +97,8 @@ __moncontrol (int mode) { struct gmonparam *p = &_gmonparam; - /* Don't change the state if we ran into an error. */ - if (p->state == GMON_PROF_ERROR) - return; - - if (mode) + /* Treat start request as stop if error or gmon not initialized. */ + if (mode && p->state != GMON_PROF_ERROR && p->tos != NULL) { /* start */ __profil((void *) p->kcount, p->kcountsize, p->lowpc, s_scale); @@ -111,7 +108,9 @@ __moncontrol (int mode) { /* stop */ __profil(NULL, 0, 0, 0); - p->state = GMON_PROF_OFF; + /* Don't change the state if we ran into an error. */ + if (p->state != GMON_PROF_ERROR) + p->state = GMON_PROF_OFF; } } libc_hidden_def (__moncontrol) @@ -125,6 +124,14 @@ __monstartup (u_long lowpc, u_long highpc) char *cp; struct gmonparam *p = &_gmonparam; + /* + * If we are incorrectly called twice in a row (without an + * intervening call to _mcleanup), ignore the second call to + * prevent leaking memory. + */ + if (p->tos != NULL) + return; + /* * round lowpc and highpc to multiples of the density we're using * so the rest of the scaling (here and in gprof) stays in ints. @@ -440,9 +447,14 @@ _mcleanup (void) { __moncontrol (0); - if (_gmonparam.state != GMON_PROF_ERROR) + if (_gmonparam.state != GMON_PROF_ERROR && _gmonparam.tos != NULL) write_gmon (); /* free the memory. */ free (_gmonparam.tos); + + /* reset buffer to initial state for safety */ + memset(&_gmonparam, 0, sizeof _gmonparam); + /* somewhat confusingly, ON=0, OFF=3 */ + _gmonparam.state = GMON_PROF_OFF; } diff --git a/gmon/tst-mcleanup.c b/gmon/tst-mcleanup.c new file mode 100644 index 0000000000..b259653ec8 --- /dev/null +++ b/gmon/tst-mcleanup.c @@ -0,0 +1,31 @@ +/* Test program for repeated invocation of _mcleanup + Copyright The GNU Toolchain Authors. + This file is part of the GNU C Library. + + The GNU C Library is free software; you can redistribute it and/or + modify it under the terms of the GNU Lesser General Public + License as published by the Free Software Foundation; either + version 2.1 of the License, or (at your option) any later version. + + The GNU C Library is distributed in the hope that it will be useful, + but WITHOUT ANY WARRANTY; without even the implied warranty of + MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU + Lesser General Public License for more details. + + You should have received a copy of the GNU Lesser General Public + License along with the GNU C Library; if not, see + . */ + +/* Intentionally calls _mcleanup() twice: once manually, it will be + called again as an atexit handler. This is incorrect use of the API, + but the point of the test is to make sure we don't crash when the + API is misused in this way. */ + +#include + +int +main (void) +{ + _mcleanup(); + return 0; +}