Fix stack overflow with huge PT_NOTE segment [BZ #20419]

A PT_NOTE in a binary could be arbitratily large, so using alloca
for it may cause stack overflow.  If the note is larger than
__MAX_ALLOCA_CUTOFF, use dynamically allocated memory to read it in.

2018-05-05  Paul Pluzhnikov  <ppluzhnikov@google.com>

	[BZ #20419]
	* elf/dl-load.c (open_verify): Fix stack overflow.
	* elf/Makefile (tst-big-note): New test.
	* elf/tst-big-note-lib.S: New.
	* elf/tst-big-note.c: New.

(cherry picked from commit 0065aaaaae)
This commit is contained in:
Paul Pluzhnikov 2018-05-05 18:08:27 -07:00 committed by Fangrui Song
parent b3356fb4a1
commit c13e59843a
5 changed files with 86 additions and 4 deletions

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@ -1,3 +1,11 @@
2018-05-05 Paul Pluzhnikov <ppluzhnikov@google.com>
[BZ #20419]
* elf/dl-load.c (open_verify): Fix stack overflow.
* elf/Makefile (tst-big-note): New test.
* elf/tst-big-note-lib.S: New.
* elf/tst-big-note.c: New.
2018-05-04 Stefan Liebler <stli@linux.vnet.ibm.com>
[BZ #23137]

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@ -191,7 +191,7 @@ tests += restest1 preloadtest loadfail multiload origtest resolvfail \
tst-tlsalign tst-tlsalign-extern tst-nodelete-opened \
tst-nodelete2 tst-audit11 tst-audit12 tst-dlsym-error tst-noload \
tst-latepthread tst-tls-manydynamic tst-nodelete-dlclose \
tst-debug1 tst-main1
tst-debug1 tst-main1 tst-big-note
# reldep9
tests-internal += loadtest unload unload2 circleload1 \
neededtest neededtest2 neededtest3 neededtest4 \
@ -279,7 +279,9 @@ modules-names = testobj1 testobj2 testobj3 testobj4 testobj5 testobj6 \
tst-latepthreadmod $(tst-tls-many-dynamic-modules) \
tst-nodelete-dlclose-dso tst-nodelete-dlclose-plugin \
tst-dlopen-offset-mod1 tst-dlopen-offset-mod2 tst-dlopen-offset-mod3 \
tst-main1mod tst-libc_dlvsym-dso
tst-main1mod tst-libc_dlvsym-dso \
tst-big-note-lib
ifeq (yes,$(have-mtls-dialect-gnu2))
tests += tst-gnu2-tls1
modules-names += tst-gnu2-tls1mod
@ -1460,9 +1462,12 @@ tst-libc_dlvsym-static-ENV = \
LD_LIBRARY_PATH=$(objpfx):$(common-objpfx):$(common-objpfx)dlfcn
$(objpfx)tst-libc_dlvsym-static.out: $(objpfx)tst-libc_dlvsym-dso.so
$(objpfx)tst-dlopen-offset: $(libdl)
$(objpfx)tst-dlopen-offset.out: $(objpfx)tst-dlopen-offset-comb.so
$(objpfx)tst-dlopen-offset-comb.so: $(objpfx)tst-dlopen-offset-mod1.so $(objpfx)tst-dlopen-offset-mod2.so $(objpfx)tst-dlopen-offset-mod3.so
dd if=$(objpfx)tst-dlopen-offset-mod1.so of=$(objpfx)tst-dlopen-offset-comb.so bs=1024 seek=64
dd if=$(objpfx)tst-dlopen-offset-mod2.so of=$(objpfx)tst-dlopen-offset-comb.so bs=1024 seek=128
dd if=$(objpfx)tst-dlopen-offset-mod3.so of=$(objpfx)tst-dlopen-offset-comb.so bs=1024 seek=192
$(objpfx)tst-big-note: $(objpfx)tst-big-note-lib.so

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@ -1511,6 +1511,7 @@ open_verify (const char *name, int fd, off_t offset,
ElfW(Ehdr) *ehdr;
ElfW(Phdr) *phdr, *ph;
ElfW(Word) *abi_note;
ElfW(Word) *abi_note_malloced = NULL;
unsigned int osversion;
size_t maplength;
@ -1685,10 +1686,25 @@ open_verify (const char *name, int fd, off_t offset,
abi_note = (void *) (fbp->buf + ph->p_offset);
else
{
abi_note = alloca (size);
/* Note: __libc_use_alloca is not usable here, because
thread info may not have been set up yet. */
if (size < __MAX_ALLOCA_CUTOFF)
abi_note = alloca (size);
else
{
/* There could be multiple PT_NOTEs. */
abi_note_malloced = realloc (abi_note_malloced, size);
if (abi_note_malloced == NULL)
goto read_error;
abi_note = abi_note_malloced;
}
__lseek (fd, ph->p_offset, SEEK_SET);
if (__libc_read (fd, (void *) abi_note, size) != size)
goto read_error;
{
free (abi_note_malloced);
goto read_error;
}
}
while (memcmp (abi_note, &expected_note, sizeof (expected_note)))
@ -1723,6 +1739,7 @@ open_verify (const char *name, int fd, off_t offset,
break;
}
free (abi_note_malloced);
}
return fd;

26
elf/tst-big-note-lib.S Normal file
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@ -0,0 +1,26 @@
/* Bug 20419: test for stack overflow in elf/dl-load.c open_verify()
Copyright (C) 2018 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
<http://www.gnu.org/licenses/>. */
/* This creates a .so with 8MiB PT_NOTE segment.
On a typical Linux system with 8MiB "ulimit -s", that was enough
to trigger stack overflow in open_verify. */
.pushsection .note.big,"a"
.balign 4
.fill 8*1024*1024, 1, 0
.popsection

26
elf/tst-big-note.c Normal file
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@ -0,0 +1,26 @@
/* Bug 20419: test for stack overflow in elf/dl-load.c open_verify()
Copyright (C) 2018 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
<http://www.gnu.org/licenses/>. */
/* This file must be run from within a directory called "elf". */
int main (int argc, char *argv[])
{
/* Nothing to do here: merely linking against tst-big-note-lib.so triggers
the bug. */
return 0;
}