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gmon: Various bug fixes (#2180155) 

Resolves: #2180155
This commit is contained in:
Florian Weimer 2023-05-22 15:22:04 +02:00
parent 3d2d551003
commit e29aaea52c
4 changed files with 745 additions and 1 deletions
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commit 801af9fafd4689337ebf27260aa115335a0cb2bc
Author: Леонид Юрьев (Leonid Yuriev) <leo@yuriev.ru>
Date: Sat Feb 4 14:41:38 2023 +0300
gmon: Fix allocated buffer overflow (bug 29444)
The `__monstartup()` allocates a buffer used to store all the data
accumulated by the monitor.
The size of this buffer depends on the size of the internal structures
used and the address range for which the monitor is activated, as well
as on the maximum density of call instructions and/or callable functions
that could be potentially on a segment of executable code.
In particular a hash table of arcs is placed at the end of this buffer.
The size of this hash table is calculated in bytes as
p->fromssize = p->textsize / HASHFRACTION;
but actually should be
p->fromssize = ROUNDUP(p->textsize / HASHFRACTION, sizeof(*p->froms));
This results in writing beyond the end of the allocated buffer when an
added arc corresponds to a call near from the end of the monitored
address range, since `_mcount()` check the incoming caller address for
monitored range but not the intermediate result hash-like index that
uses to write into the table.
It should be noted that when the results are output to `gmon.out`, the
table is read to the last element calculated from the allocated size in
bytes, so the arcs stored outside the buffer boundary did not fall into
`gprof` for analysis. Thus this "feature" help me to found this bug
during working with https://sourceware.org/bugzilla/show_bug.cgi?id=29438
Just in case, I will explicitly note that the problem breaks the
`make test t=gmon/tst-gmon-dso` added for Bug 29438.
There, the arc of the `f3()` call disappears from the output, since in
the DSO case, the call to `f3` is located close to the end of the
monitored range.
Signed-off-by: Леонид Юрьев (Leonid Yuriev) <leo@yuriev.ru>
Another minor error seems a related typo in the calculation of
`kcountsize`, but since kcounts are smaller than froms, this is
actually to align the p->froms data.
Co-authored-by: DJ Delorie <dj@redhat.com>
Reviewed-by: Carlos O'Donell <carlos@redhat.com>
diff --git a/gmon/gmon.c b/gmon/gmon.c
index dee64803ada583d7..bf76358d5b1aa2da 100644
--- a/gmon/gmon.c
+++ b/gmon/gmon.c
@@ -132,6 +132,8 @@ __monstartup (u_long lowpc, u_long highpc)
p->lowpc = ROUNDDOWN(lowpc, HISTFRACTION * sizeof(HISTCOUNTER));
p->highpc = ROUNDUP(highpc, HISTFRACTION * sizeof(HISTCOUNTER));
p->textsize = p->highpc - p->lowpc;
+ /* This looks like a typo, but it's here to align the p->froms
+ section. */
p->kcountsize = ROUNDUP(p->textsize / HISTFRACTION, sizeof(*p->froms));
p->hashfraction = HASHFRACTION;
p->log_hashfraction = -1;
@@ -142,7 +144,7 @@ __monstartup (u_long lowpc, u_long highpc)
instead of integer division. Precompute shift amount. */
p->log_hashfraction = ffs(p->hashfraction * sizeof(*p->froms)) - 1;
}
- p->fromssize = p->textsize / HASHFRACTION;
+ p->fromssize = ROUNDUP(p->textsize / HASHFRACTION, sizeof(*p->froms));
p->tolimit = p->textsize * ARCDENSITY / 100;
if (p->tolimit < MINARCS)
p->tolimit = MINARCS;

477
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This patch adds the required @order directives to preserve the
GLIBC_PRIVATE ABI.
commit 31be941e4367c001b2009308839db5c67bf9dcbc
Author: Simon Kissane <skissane@gmail.com>
Date: Sat Feb 11 20:12:13 2023 +1100
gmon: improve mcount overflow handling [BZ# 27576]
When mcount overflows, no gmon.out file is generated, but no message is printed
to the user, leaving the user with no idea why, and thinking maybe there is
some bug - which is how BZ 27576 ended up being logged. Print a message to
stderr in this case so the user knows what is going on.
As a comment in sys/gmon.h acknowledges, the hardcoded MAXARCS value is too
small for some large applications, including the test case in that BZ. Rather
than increase it, add tunables to enable MINARCS and MAXARCS to be overridden
at runtime (glibc.gmon.minarcs and glibc.gmon.maxarcs). So if a user gets the
mcount overflow error, they can try increasing maxarcs (they might need to
increase minarcs too if the heuristic is wrong in their case.)
Note setting minarcs/maxarcs too large can cause monstartup to fail with an
out of memory error. If you set them large enough, it can cause an integer
overflow in calculating the buffer size. I haven't done anything to defend
against that - it would not generally be a security vulnerability, since these
tunables will be ignored in suid/sgid programs (due to the SXID_ERASE default),
and if you can set GLIBC_TUNABLES in the environment of a process, you can take
it over anyway (LD_PRELOAD, LD_LIBRARY_PATH, etc). I thought about modifying
the code of monstartup to defend against integer overflows, but doing so is
complicated, and I realise the existing code is susceptible to them even prior
to this change (e.g. try passing a pathologically large highpc argument to
monstartup), so I decided just to leave that possibility in-place.
Add a test case which demonstrates mcount overflow and the tunables.
Document the new tunables in the manual.
Signed-off-by: Simon Kissane <skissane@gmail.com>
Reviewed-by: DJ Delorie <dj@redhat.com>
Conflicts:
manual/tunables.texi
(missing tunables downstream)
diff --git a/elf/dl-tunables.list b/elf/dl-tunables.list
index f11ca5b3e8b09b43..dc2999796042dbaf 100644
--- a/elf/dl-tunables.list
+++ b/elf/dl-tunables.list
@@ -149,4 +149,17 @@ glibc {
default: 2
}
}
+
+ gmon {
+ minarcs {
+ type: INT_32
+ minval: 50
+ default: 50
+ }
+ maxarcs {
+ type: INT_32
+ minval: 50
+ default: 1048576
+ }
+ }
}
diff --git a/gmon/Makefile b/gmon/Makefile
index d94593c9d8a882eb..54f05894d4dd8c4a 100644
--- a/gmon/Makefile
+++ b/gmon/Makefile
@@ -25,7 +25,7 @@ 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-mcount-overflow
ifeq ($(build-profile),yes)
tests += tst-profile-static
tests-static += tst-profile-static
@@ -56,6 +56,18 @@ ifeq ($(run-built-tests),yes)
tests-special += $(objpfx)tst-gmon-gprof.out
endif
+CFLAGS-tst-mcount-overflow.c := -fno-omit-frame-pointer -pg
+tst-mcount-overflow-no-pie = yes
+CRT-tst-mcount-overflow := $(csu-objpfx)g$(start-installed-name)
+# Intentionally use invalid config where maxarcs<minarcs to check warning is printed
+tst-mcount-overflow-ENV := GMON_OUT_PREFIX=$(objpfx)tst-mcount-overflow.data \
+ GLIBC_TUNABLES=glibc.gmon.minarcs=51:glibc.gmon.maxarcs=50
+# Send stderr into output file because we make sure expected messages are printed
+tst-mcount-overflow-ARGS := 2>&1 1>/dev/null | cat
+ifeq ($(run-built-tests),yes)
+tests-special += $(objpfx)tst-mcount-overflow-check.out
+endif
+
CFLAGS-tst-gmon-static.c := $(PIE-ccflag) -fno-omit-frame-pointer -pg
CRT-tst-gmon-static := $(csu-objpfx)gcrt1.o
tst-gmon-static-no-pie = yes
@@ -103,6 +115,14 @@ $(objpfx)tst-gmon.out: clean-tst-gmon-data
clean-tst-gmon-data:
rm -f $(objpfx)tst-gmon.data.*
+$(objpfx)tst-mcount-overflow.o: clean-tst-mcount-overflow-data
+clean-tst-mcount-overflow-data:
+ rm -f $(objpfx)tst-mcount-overflow.data.*
+
+$(objpfx)tst-mcount-overflow-check.out: tst-mcount-overflow-check.sh $(objpfx)tst-mcount-overflow.out
+ $(SHELL) $< $(objpfx)tst-mcount-overflow > $@; \
+ $(evaluate-test)
+
$(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 bf76358d5b1aa2da..689bf80141e559ca 100644
--- a/gmon/gmon.c
+++ b/gmon/gmon.c
@@ -46,6 +46,11 @@
#include <libc-internal.h>
#include <not-cancel.h>
+#if HAVE_TUNABLES
+# define TUNABLE_NAMESPACE gmon
+# include <elf/dl-tunables.h>
+#endif
+
#ifdef PIC
# include <link.h>
@@ -124,6 +129,22 @@ __monstartup (u_long lowpc, u_long highpc)
int o;
char *cp;
struct gmonparam *p = &_gmonparam;
+ long int minarcs, maxarcs;
+
+#if HAVE_TUNABLES
+ /* Read minarcs/maxarcs tunables. */
+ minarcs = TUNABLE_GET (minarcs, int32_t, NULL);
+ maxarcs = TUNABLE_GET (maxarcs, int32_t, NULL);
+ if (maxarcs < minarcs)
+ {
+ ERR("monstartup: maxarcs < minarcs, setting maxarcs = minarcs\n");
+ maxarcs = minarcs;
+ }
+#else
+ /* No tunables, we use hardcoded defaults */
+ minarcs = MINARCS;
+ maxarcs = MAXARCS;
+#endif
/*
* round lowpc and highpc to multiples of the density we're using
@@ -146,10 +167,10 @@ __monstartup (u_long lowpc, u_long highpc)
}
p->fromssize = ROUNDUP(p->textsize / HASHFRACTION, sizeof(*p->froms));
p->tolimit = p->textsize * ARCDENSITY / 100;
- if (p->tolimit < MINARCS)
- p->tolimit = MINARCS;
- else if (p->tolimit > MAXARCS)
- p->tolimit = MAXARCS;
+ if (p->tolimit < minarcs)
+ p->tolimit = minarcs;
+ else if (p->tolimit > maxarcs)
+ p->tolimit = maxarcs;
p->tossize = p->tolimit * sizeof(struct tostruct);
cp = calloc (p->kcountsize + p->fromssize + p->tossize, 1);
diff --git a/gmon/mcount.c b/gmon/mcount.c
index 9d4a1a50fa6ab21a..f7180fdb83399a14 100644
--- a/gmon/mcount.c
+++ b/gmon/mcount.c
@@ -41,6 +41,10 @@ static char sccsid[] = "@(#)mcount.c 8.1 (Berkeley) 6/4/93";
#include <atomic.h>
+#include <not-cancel.h>
+#include <unistd.h>
+#define ERR(s) __write_nocancel (STDERR_FILENO, s, sizeof (s) - 1)
+
/*
* mcount is called on entry to each function compiled with the profiling
* switch set. _mcount(), which is declared in a machine-dependent way
@@ -170,6 +174,7 @@ done:
return;
overflow:
p->state = GMON_PROF_ERROR;
+ ERR("mcount: call graph buffer size limit exceeded, gmon.out will not be generated\n");
return;
}
diff --git a/gmon/sys/gmon.h b/gmon/sys/gmon.h
index b4cc3b043a2aec77..af0582a3717085b5 100644
--- a/gmon/sys/gmon.h
+++ b/gmon/sys/gmon.h
@@ -111,6 +111,8 @@ extern struct __bb *__bb_head;
* Always allocate at least this many tostructs. This
* hides the inadequacy of the ARCDENSITY heuristic, at least
* for small programs.
+ *
+ * Value can be overridden at runtime by glibc.gmon.minarcs tunable.
*/
#define MINARCS 50
@@ -124,8 +126,8 @@ extern struct __bb *__bb_head;
* Used to be max representable value of ARCINDEX minus 2, but now
* that ARCINDEX is a long, that's too large; we don't really want
* to allow a 48 gigabyte table.
- * The old value of 1<<16 wasn't high enough in practice for large C++
- * programs; will 1<<20 be adequate for long? FIXME
+ *
+ * Value can be overridden at runtime by glibc.gmon.maxarcs tunable.
*/
#define MAXARCS (1 << 20)
diff --git a/gmon/tst-mcount-overflow-check.sh b/gmon/tst-mcount-overflow-check.sh
new file mode 100644
index 0000000000000000..27eb5538fd573a6e
--- /dev/null
+++ b/gmon/tst-mcount-overflow-check.sh
@@ -0,0 +1,45 @@
+#!/bin/sh
+# Test expected messages generated when mcount overflows
+# Copyright (C) 2017-2023 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
+# 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
+# <https://www.gnu.org/licenses/>.
+
+LC_ALL=C
+export LC_ALL
+set -e
+exec 2>&1
+
+program="$1"
+
+check_msg() {
+ if ! grep -q "$1" "$program.out"; then
+ echo "FAIL: expected message not in output: $1"
+ exit 1
+ fi
+}
+
+check_msg 'monstartup: maxarcs < minarcs, setting maxarcs = minarcs'
+check_msg 'mcount: call graph buffer size limit exceeded, gmon.out will not be generated'
+
+for data_file in $1.data.*; do
+ if [ -f "$data_file" ]; then
+ echo "FAIL: expected no data files, but found $data_file"
+ exit 1
+ fi
+done
+
+echo PASS
diff --git a/gmon/tst-mcount-overflow.c b/gmon/tst-mcount-overflow.c
new file mode 100644
index 0000000000000000..06cc93ef872eb7c1
--- /dev/null
+++ b/gmon/tst-mcount-overflow.c
@@ -0,0 +1,72 @@
+/* Test program to trigger mcount overflow in profiling collection.
+ Copyright (C) 2017-2023 Free Software Foundation, Inc.
+ 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
+ <https://www.gnu.org/licenses/>. */
+
+/* Program with sufficiently complex, yet pointless, call graph
+ that it will trigger an mcount overflow, when you set the
+ minarcs/maxarcs tunables to very low values. */
+
+#define PREVENT_TAIL_CALL asm volatile ("")
+
+/* Calls REP(n) macro 16 times, for n=0..15.
+ * You need to define REP(n) before using this.
+ */
+#define REPS \
+ REP(0) REP(1) REP(2) REP(3) REP(4) REP(5) REP(6) REP(7) \
+ REP(8) REP(9) REP(10) REP(11) REP(12) REP(13) REP(14) REP(15)
+
+/* Defines 16 leaf functions named f1_0 to f1_15 */
+#define REP(n) \
+ __attribute__ ((noinline, noclone, weak)) void f1_##n (void) {};
+REPS
+#undef REP
+
+/* Calls all 16 leaf functions f1_* in succession */
+__attribute__ ((noinline, noclone, weak)) void
+f2 (void)
+{
+# define REP(n) f1_##n();
+ REPS
+# undef REP
+ PREVENT_TAIL_CALL;
+}
+
+/* Defines 16 functions named f2_0 to f2_15, which all just call f2 */
+#define REP(n) \
+ __attribute__ ((noinline, noclone, weak)) void \
+ f2_##n (void) { f2(); PREVENT_TAIL_CALL; };
+REPS
+#undef REP
+
+__attribute__ ((noinline, noclone, weak)) void
+f3 (int count)
+{
+ for (int i = 0; i < count; ++i)
+ {
+ /* Calls f1_0(), f2_0(), f1_1(), f2_1(), f3_0(), etc */
+# define REP(n) f1_##n(); f2_##n();
+ REPS
+# undef REP
+ }
+}
+
+int
+main (void)
+{
+ f3 (1000);
+ return 0;
+}
diff --git a/manual/tunables.texi b/manual/tunables.texi
index 7b70e80391ee87f7..00eafcf44b562b9e 100644
--- a/manual/tunables.texi
+++ b/manual/tunables.texi
@@ -73,6 +73,9 @@ glibc.malloc.check: 0 (min: 0, max: 3)
* Elision Tunables:: Tunables in elision subsystem
* Hardware Capability Tunables:: Tunables that modify the hardware
capabilities seen by @theglibc{}
+* gmon Tunables:: Tunables that control the gmon profiler, used in
+ conjunction with gprof
+
@end menu
@node Tunable names
@@ -506,3 +509,59 @@ instead.
This tunable is specific to i386 and x86-64.
@end deftp
+
+@node gmon Tunables
+@section gmon Tunables
+@cindex gmon tunables
+
+@deftp {Tunable namespace} glibc.gmon
+This tunable namespace affects the behaviour of the gmon profiler.
+gmon is a component of @theglibc{} which is normally used in
+conjunction with gprof.
+
+When GCC compiles a program with the @code{-pg} option, it instruments
+the program with calls to the @code{mcount} function, to record the
+program's call graph. At program startup, a memory buffer is allocated
+to store this call graph; the size of the buffer is calculated using a
+heuristic based on code size. If during execution, the buffer is found
+to be too small, profiling will be aborted and no @file{gmon.out} file
+will be produced. In that case, you will see the following message
+printed to standard error:
+
+@example
+mcount: call graph buffer size limit exceeded, gmon.out will not be generated
+@end example
+
+Most of the symbols discussed in this section are defined in the header
+@code{sys/gmon.h}. However, some symbols (for example @code{mcount})
+are not defined in any header file, since they are only intended to be
+called from code generated by the compiler.
+@end deftp
+
+@deftp Tunable glibc.mem.minarcs
+The heuristic for sizing the call graph buffer is known to be
+insufficient for small programs; hence, the calculated value is clamped
+to be at least a minimum size. The default minimum (in units of
+call graph entries, @code{struct tostruct}), is given by the macro
+@code{MINARCS}. If you have some program with an unusually complex
+call graph, for which the heuristic fails to allocate enough space,
+you can use this tunable to increase the minimum to a larger value.
+@end deftp
+
+@deftp Tunable glibc.mem.maxarcs
+To prevent excessive memory consumption when profiling very large
+programs, the call graph buffer is allowed to have a maximum of
+@code{MAXARCS} entries. For some very large programs, the default
+value of @code{MAXARCS} defined in @file{sys/gmon.h} is too small; in
+that case, you can use this tunable to increase it.
+
+Note the value of the @code{maxarcs} tunable must be greater or equal
+to that of the @code{minarcs} tunable; if this constraint is violated,
+a warning will printed to standard error at program startup, and
+the @code{minarcs} value will be used as the maximum as well.
+
+Setting either tunable too high may result in a call graph buffer
+whose size exceeds the available memory; in that case, an out of memory
+error will be printed at program startup, the profiler will be
+disabled, and no @file{gmon.out} file will be generated.
+@end deftp
diff --git a/sysdeps/unix/sysv/linux/aarch64/dl-tunables.list b/sysdeps/unix/sysv/linux/aarch64/dl-tunables.list
index 5c3c5292025607a1..265f82ef2be42fd0 100644
--- a/sysdeps/unix/sysv/linux/aarch64/dl-tunables.list
+++ b/sysdeps/unix/sysv/linux/aarch64/dl-tunables.list
@@ -24,3 +24,7 @@
# Tunables added in RHEL 8.8.0
@order glibc.rtld.dynamic_sort
+
+# Tunables added in RHEL 8.9.0
+@order glibc.gmon.minarcs
+@order glibc.gmon.maxarcs
diff --git a/sysdeps/unix/sysv/linux/i386/dl-tunables.list b/sysdeps/unix/sysv/linux/i386/dl-tunables.list
index b9cad4af62d9f2e5..9c1ccb86501c61e7 100644
--- a/sysdeps/unix/sysv/linux/i386/dl-tunables.list
+++ b/sysdeps/unix/sysv/linux/i386/dl-tunables.list
@@ -31,3 +31,7 @@
# Tunables added in RHEL 8.8.0
@order glibc.rtld.dynamic_sort
+
+# Tunables added in RHEL 8.9.0
+@order glibc.gmon.minarcs
+@order glibc.gmon.maxarcs
diff --git a/sysdeps/unix/sysv/linux/powerpc/powerpc64/le/dl-tunables.list b/sysdeps/unix/sysv/linux/powerpc/powerpc64/le/dl-tunables.list
index ee1e6fca95e1f2da..c8bb1a8ec0283ac8 100644
--- a/sysdeps/unix/sysv/linux/powerpc/powerpc64/le/dl-tunables.list
+++ b/sysdeps/unix/sysv/linux/powerpc/powerpc64/le/dl-tunables.list
@@ -24,3 +24,7 @@
# Tunables added in RHEL 8.8.0
@order glibc.rtld.dynamic_sort
+
+# Tunables added in RHEL 8.9.0
+@order glibc.gmon.minarcs
+@order glibc.gmon.maxarcs
diff --git a/sysdeps/unix/sysv/linux/s390/s390-64/dl-tunables.list b/sysdeps/unix/sysv/linux/s390/s390-64/dl-tunables.list
index 099e28d8f8e67944..85b3a014ffcadc45 100644
--- a/sysdeps/unix/sysv/linux/s390/s390-64/dl-tunables.list
+++ b/sysdeps/unix/sysv/linux/s390/s390-64/dl-tunables.list
@@ -23,3 +23,7 @@
# Tunables added in RHEL 8.8.0
@order glibc.rtld.dynamic_sort
+
+# Tunables added in RHEL 8.9.0
+@order glibc.gmon.minarcs
+@order glibc.gmon.maxarcs
diff --git a/sysdeps/unix/sysv/linux/x86_64/64/dl-tunables.list b/sysdeps/unix/sysv/linux/x86_64/64/dl-tunables.list
index b9cad4af62d9f2e5..9c1ccb86501c61e7 100644
--- a/sysdeps/unix/sysv/linux/x86_64/64/dl-tunables.list
+++ b/sysdeps/unix/sysv/linux/x86_64/64/dl-tunables.list
@@ -31,3 +31,7 @@
# Tunables added in RHEL 8.8.0
@order glibc.rtld.dynamic_sort
+
+# Tunables added in RHEL 8.9.0
+@order glibc.gmon.minarcs
+@order glibc.gmon.maxarcs

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@ -0,0 +1,191 @@
commit bde121872001d8f3224eeafa5b7effb871c3fbca
Author: Simon Kissane <skissane@gmail.com>
Date: Sat Feb 11 08:58:02 2023 +1100
gmon: fix memory corruption issues [BZ# 30101]
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 <skissane@gmail.com>
Reviewed-by: DJ Delorie <dj@redhat.com>
Conflicts:
gmon/Makefile
(copyright year update)
diff --git a/gmon/Makefile b/gmon/Makefile
index 54f05894d4dd8c4a..1bc4ad6e14e292a9 100644
--- a/gmon/Makefile
+++ b/gmon/Makefile
@@ -1,4 +1,5 @@
-# Copyright (C) 1995-2018 Free Software Foundation, Inc.
+# 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 tst-mcount-overflow
+tests = tst-sprofil tst-gmon tst-mcount-overflow tst-mcleanup
ifeq ($(build-profile),yes)
tests += tst-profile-static
tests-static += tst-profile-static
@@ -68,6 +69,14 @@ ifeq ($(run-built-tests),yes)
tests-special += $(objpfx)tst-mcount-overflow-check.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)gcrt1.o
tst-gmon-static-no-pie = yes
@@ -123,6 +132,10 @@ $(objpfx)tst-mcount-overflow-check.out: tst-mcount-overflow-check.sh $(objpfx)ts
$(SHELL) $< $(objpfx)tst-mcount-overflow > $@; \
$(evaluate-test)
+$(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 689bf80141e559ca..5e99a7351dc71666 100644
--- a/gmon/gmon.c
+++ b/gmon/gmon.c
@@ -102,11 +102,8 @@ __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);
@@ -116,7 +113,9 @@ __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)
@@ -146,6 +145,14 @@ __monstartup (u_long lowpc, u_long highpc)
maxarcs = MAXARCS;
#endif
+ /*
+ * 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.
@@ -463,9 +470,14 @@ _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 0000000000000000..b259653ec833aca4
--- /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
+ <https://www.gnu.org/licenses/>. */
+
+/* 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 <sys/gmon.h>
+
+int
+main (void)
+{
+ _mcleanup();
+ return 0;
+}

8
glibc.spec
View File

@ -1,6 +1,6 @@
%define glibcsrcdir glibc-2.28
%define glibcversion 2.28
%define glibcrelease 227%{?dist}
%define glibcrelease 228%{?dist}
# Pre-release tarballs are pulled in from git using a command that is
# effectively:
#
@ -1034,6 +1034,9 @@ Patch841: glibc-rh2154914-2.patch
Patch842: glibc-rh2183081-1.patch
Patch843: glibc-rh2183081-2.patch
Patch844: glibc-rh2172949.patch
Patch845: glibc-rh2180155-1.patch
Patch846: glibc-rh2180155-2.patch
Patch847: glibc-rh2180155-3.patch
##############################################################################
# Continued list of core "glibc" package information:
@ -2864,6 +2867,9 @@ fi
%files -f compat-libpthread-nonshared.filelist -n compat-libpthread-nonshared
%changelog
* Mon May 22 2023 Florian Weimer <fweimer@redhat.com> - 2.28-228
- gmon: Various bug fixes (#2180155)
* Thu May 18 2023 Patsy Griffin <patsy@redhat.com> - 2.28-227
- Change sgetsgent_r to set errno. (#2172949)