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Revision 246c320a8cfe0b11d81a4af38fa9985ef0cc9a4c authored by Kirill A. Shutemov on 24 July 2020, 04:15:11 UTC, committed by Linus Torvalds on 24 July 2020, 19:42:41 UTC 
mm/mmap.c: close race between munmap() and expand_upwards()/downwards()
 
VMA with VM_GROWSDOWN or VM_GROWSUP flag set can change their size under
mmap_read_lock().  It can lead to race with __do_munmap():

	Thread A			Thread B
__do_munmap()
  detach_vmas_to_be_unmapped()
  mmap_write_downgrade()
				expand_downwards()
				  vma->vm_start = address;
				  // The VMA now overlaps with
				  // VMAs detached by the Thread A
				// page fault populates expanded part
				// of the VMA
  unmap_region()
    // Zaps pagetables partly
    // populated by Thread B

Similar race exists for expand_upwards().

The fix is to avoid downgrading mmap_lock in __do_munmap() if detached
VMAs are next to VM_GROWSDOWN or VM_GROWSUP VMA.

[akpm@linux-foundation.org: s/mmap_sem/mmap_lock/ in comment]

Fixes: dd2283f2605e ("mm: mmap: zap pages with read mmap_sem in munmap")
Reported-by: Jann Horn <jannh@google.com>
Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Reviewed-by: Yang Shi <yang.shi@linux.alibaba.com>
Acked-by: Vlastimil Babka <vbabka@suse.cz>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: <stable@vger.kernel.org>	[4.20+]
Link: http://lkml.kernel.org/r/20200709105309.42495-1-kirill.shutemov@linux.intel.com
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
1 parent f37e99a
Raw File
depmod.sh 
#!/bin/sh
# SPDX-License-Identifier: GPL-2.0
#
# A depmod wrapper used by the toplevel Makefile

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

if ! test -r System.map ; then
	echo "Warning: modules_install: missing 'System.map' file. Skipping depmod." >&2
	exit 0
fi

if [ -z $(command -v $DEPMOD) ]; then
	echo "Warning: 'make modules_install' requires $DEPMOD. Please install it." >&2
	echo "This is probably in the kmod package." >&2
	exit 0
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"
ret=$?

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

exit $ret
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