commit 80c570537e380c1b8e48754c0ddbce2abcde2d00

Author: Jan Kratochvil <jan.kratochvil@redhat.com>

Date:   Thu Feb 26 14:08:01 2015 +0100

    SEGV in ppc64_elf_get_synthetic_symtab reading a separate debug file

    The attached patch fixes the SEGV and lets GDB successfully

    load all kernel modules installed by default on RHEL 7.

    Valgrind on F-21 x86_64 host has shown me more clear what is the problem:

    Reading symbols from /home/jkratoch/t/cordic.ko...Reading symbols from

    /home/jkratoch/t/cordic.ko.debug...=================================================================

    ==22763==ERROR: AddressSanitizer: heap-use-after-free on address 0x6120000461c8 at pc 0x150cdbd bp 0x7fffffffc7e0 sp 0x7fffffffc7d0

    READ of size 8 at 0x6120000461c8 thread T0

        #0 0x150cdbc in ppc64_elf_get_synthetic_symtab /home/jkratoch/redhat/gdb-test-asan/bfd/elf64-ppc.c:3282

        #1 0x8c5274 in elf_read_minimal_symbols /home/jkratoch/redhat/gdb-test-asan/gdb/elfread.c:1205

        #2 0x8c55e7 in elf_symfile_read /home/jkratoch/redhat/gdb-test-asan/gdb/elfread.c:1268

    [...]

    0x6120000461c8 is located 264 bytes inside of 288-byte region [0x6120000460c0,0x6120000461e0)

    freed by thread T0 here:

        #0 0x7ffff715454f in __interceptor_free (/lib64/libasan.so.1+0x5754f)

        #1 0xde9cde in xfree common/common-utils.c:98

        #2 0x9a04f7 in do_my_cleanups common/cleanups.c:155

        #3 0x9a05d3 in do_cleanups common/cleanups.c:177

        #4 0x8c538a in elf_read_minimal_symbols /home/jkratoch/redhat/gdb-test-asan/gdb/elfread.c:1229

        #5 0x8c55e7 in elf_symfile_read /home/jkratoch/redhat/gdb-test-asan/gdb/elfread.c:1268

    [...]

    previously allocated by thread T0 here:

        #0 0x7ffff71547c7 in malloc (/lib64/libasan.so.1+0x577c7)

        #1 0xde9b95 in xmalloc common/common-utils.c:41

        #2 0x8c4da2 in elf_read_minimal_symbols /home/jkratoch/redhat/gdb-test-asan/gdb/elfread.c:1147

        #3 0x8c55e7 in elf_symfile_read /home/jkratoch/redhat/gdb-test-asan/gdb/elfread.c:1268

    [...]

    SUMMARY: AddressSanitizer: heap-use-after-free /home/jkratoch/redhat/gdb-test-asan/bfd/elf64-ppc.c:3282 ppc64_elf_get_synthetic_symtab

    [...]

    ==22763==ABORTING

    A similar case a few lines later I have fixed in 2010 by:

            https://sourceware.org/git/?p=binutils-gdb.git;a=commit;h=3f1eff0a2c7f0e7078f011f55b8e7f710aae0cc2

    My testcase does not always reproduce it but at least a bit:

     * GDB without ppc64 target (even as a secondary one) is reported as "untested"

     * ASAN-built GDB with ppc64 target always crashes (and PASSes with this fix)

     * unpatched non-ASAN-built GDB with ppc64 target crashes from commandline

     * unpatched non-ASAN-built GDB with ppc64 target PASSes from runtest (?)

    gdb/ChangeLog

    2015-02-26  Jan Kratochvil  <jan.kratochvil@redhat.com>

    	* elfread.c (elf_read_minimal_symbols): Use bfd_alloc for

    	bfd_canonicalize_symtab.

    gdb/testsuite/ChangeLog

    2015-02-26  Jan Kratochvil  <jan.kratochvil@redhat.com>

    	* gdb.arch/cordic.ko.bz2: New file.

    	* gdb.arch/cordic.ko.debug.bz2: New file.

    	* gdb.arch/ppc64-symtab-cordic.exp: New file.

Index: gdb-7.6.1/gdb/elfread.c

===================================================================

--- gdb-7.6.1.orig/gdb/elfread.c

+++ gdb-7.6.1/gdb/elfread.c

@@ -2308,8 +2308,10 @@ elf_symfile_read (struct objfile *objfil

   if (storage_needed > 0)

     {

-      symbol_table = (asymbol **) xmalloc (storage_needed);

-      make_cleanup (xfree, symbol_table);

+      /* Memory gets permanently referenced from ABFD after

+	 bfd_canonicalize_symtab so it must not get freed before ABFD gets.  */

+

+      symbol_table = bfd_alloc (abfd, storage_needed);

       symcount = bfd_canonicalize_symtab (objfile->obfd, symbol_table);

       if (symcount < 0)

Index: gdb-7.6.1/gdb/testsuite/gdb.arch/ppc64-symtab-cordic.exp

===================================================================

--- /dev/null

+++ gdb-7.6.1/gdb/testsuite/gdb.arch/ppc64-symtab-cordic.exp

@@ -0,0 +1,51 @@

+# Copyright 2015 Free Software Foundation, Inc.

+

+# This program is free software; you can redistribute it and/or modify

+# it under the terms of the GNU General Public License as published by

+# the Free Software Foundation; either version 3 of the License, or

+# (at your option) any later version.

+#

+# This program 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 General Public License for more details.

+#

+# You should have received a copy of the GNU General Public License

+# along with this program.  If not, see <http://www.gnu.org/licenses/>.

+

+standard_testfile

+

+set kobz2uufile ${srcdir}/${subdir}/cordic.ko.bz2.uu

+set kofile ${objdir}/${subdir}/cordic.ko

+set kodebugbz2uufile ${srcdir}/${subdir}/cordic.ko.debug.bz2.uu

+set kodebugfile ${objdir}/${subdir}/cordic.ko.debug

+

+if {[catch "system \"uudecode -o - ${kobz2uufile} | bzip2 -dc >${kofile}\""] != 0} {

+    untested "failed bzip2 for ${kobz2uufile}"

+    return -1

+}

+if {[catch "system \"uudecode -o - ${kodebugbz2uufile} | bzip2 -dc >${kodebugfile}\""] != 0} {

+    untested "failed bzip2 for ${kodebugbz2uufile}"

+    return -1

+}

+

+gdb_exit

+gdb_start

+gdb_reinitialize_dir $srcdir/$subdir

+

+# This test won't work properly if system debuginfo is installed.

+# Test message is suppressed by "" as otherwise we could print PASS+UNTESTED

+# result to gdb.sum making a false feeling the issue has been tested.

+gdb_test_no_output "set debug-file-directory" ""

+

+gdb_load ${kofile}

+

+set test "show architecture"

+gdb_test_multiple $test $test {

+    -re "\r\nThe target architecture is set automatically \\(currently powerpc:common64\\)\r\n$gdb_prompt $" {

+	pass $test

+    }

+    -re "\r\nThe target architecture is set automatically \\(currently .*\\)\r\n$gdb_prompt $" {

+	untested "powerpc:common64 is not supported"

+    }

+}

Index: gdb-7.6.1/gdb/testsuite/gdb.arch/cordic.ko.bz2.uu

===================================================================

--- /dev/null

+++ gdb-7.6.1/gdb/testsuite/gdb.arch/cordic.ko.bz2.uu

@@ -0,0 +1,53 @@

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Index: gdb-7.6.1/gdb/testsuite/gdb.arch/cordic.ko.debug.bz2.uu

===================================================================

--- /dev/null

+++ gdb-7.6.1/gdb/testsuite/gdb.arch/cordic.ko.debug.bz2.uu

@@ -0,0 +1,24 @@

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+`

+end