Skip to main content

Browse the archive

Revision c715b72c1ba406f133217b509044c38d8e714a37 authored by Kees Cook on 18 August 2017, 22:16:31 UTC, committed by Linus Torvalds on 18 August 2017, 22:32:02 UTC 
mm: revert x86_64 and arm64 ELF_ET_DYN_BASE base changes
 
Moving the x86_64 and arm64 PIE base from 0x555555554000 to 0x000100000000
broke AddressSanitizer.  This is a partial revert of:

  eab09532d400 ("binfmt_elf: use ELF_ET_DYN_BASE only for PIE")
  02445990a96e ("arm64: move ELF_ET_DYN_BASE to 4GB / 4MB")

The AddressSanitizer tool has hard-coded expectations about where
executable mappings are loaded.

The motivation for changing the PIE base in the above commits was to
avoid the Stack-Clash CVEs that allowed executable mappings to get too
close to heap and stack.  This was mainly a problem on 32-bit, but the
64-bit bases were moved too, in an effort to proactively protect those
systems (proofs of concept do exist that show 64-bit collisions, but
other recent changes to fix stack accounting and setuid behaviors will
minimize the impact).

The new 32-bit PIE base is fine for ASan (since it matches the ET_EXEC
base), so only the 64-bit PIE base needs to be reverted to let x86 and
arm64 ASan binaries run again.  Future changes to the 64-bit PIE base on
these architectures can be made optional once a more dynamic method for
dealing with AddressSanitizer is found.  (e.g.  always loading PIE into
the mmap region for marked binaries.)

Link: http://lkml.kernel.org/r/20170807201542.GA21271@beast
Fixes: eab09532d400 ("binfmt_elf: use ELF_ET_DYN_BASE only for PIE")
Fixes: 02445990a96e ("arm64: move ELF_ET_DYN_BASE to 4GB / 4MB")
Signed-off-by: Kees Cook <keescook@chromium.org>
Reported-by: Kostya Serebryany <kcc@google.com>
Acked-by: Will Deacon <will.deacon@arm.com>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
1 parent 704b862
Raw File
depmod.sh 
#!/bin/sh
#
# A depmod wrapper used by the toplevel Makefile

if test $# -ne 3; then
	echo "Usage: $0 /sbin/depmod <kernelrelease> <symbolprefix>" >&2
	exit 1
fi
DEPMOD=$1
KERNELRELEASE=$2
SYMBOL_PREFIX=$3

if ! test -r System.map -a -x "$DEPMOD"; then
	exit 0
fi

# older versions of depmod don't support -P <symbol-prefix>
# support was added in module-init-tools 3.13
if test -n "$SYMBOL_PREFIX"; then
	release=$("$DEPMOD" --version)
	package=$(echo "$release" | cut -d' ' -f 1)
	if test "$package" = "module-init-tools"; then
		version=$(echo "$release" | cut -d' ' -f 2)
		later=$(printf '%s\n' "$version" "3.13" | sort -V | tail -n 1)
		if test "$later" != "$version"; then
			# module-init-tools < 3.13, drop the symbol prefix
			SYMBOL_PREFIX=""
		fi
	fi
	if test -n "$SYMBOL_PREFIX"; then
		SYMBOL_PREFIX="-P $SYMBOL_PREFIX"
	fi
fi

# older versions of depmod require the version string to start with three
# numbers, so we cheat with a symlink here
depmod_hack_needed=true
tmp_dir=$(mktemp -d ${TMPDIR:-/tmp}/depmod.XXXXXX)
mkdir -p "$tmp_dir/lib/modules/$KERNELRELEASE"
if "$DEPMOD" -b "$tmp_dir" $KERNELRELEASE 2>/dev/null; then
	if test -e "$tmp_dir/lib/modules/$KERNELRELEASE/modules.dep" -o \
		-e "$tmp_dir/lib/modules/$KERNELRELEASE/modules.dep.bin"; then
		depmod_hack_needed=false
	fi
fi
rm -rf "$tmp_dir"
if $depmod_hack_needed; then
	symlink="$INSTALL_MOD_PATH/lib/modules/99.98.$KERNELRELEASE"
	ln -s "$KERNELRELEASE" "$symlink"
	KERNELRELEASE=99.98.$KERNELRELEASE
fi

set -- -ae -F System.map
if test -n "$INSTALL_MOD_PATH"; then
	set -- "$@" -b "$INSTALL_MOD_PATH"
fi
"$DEPMOD" "$@" "$KERNELRELEASE" $SYMBOL_PREFIX
ret=$?

if $depmod_hack_needed; then
	rm -f "$symlink"
fi

exit $ret
back to top