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
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
gfp-translate
#!/bin/bash
# SPDX-License-Identifier: GPL-2.0-only
# Translate the bits making up a GFP mask
# (c) 2009, Mel Gorman <mel@csn.ul.ie>
SOURCE=
GFPMASK=none
# Helper function to report failures and exit
die() {
echo ERROR: $@
if [ "$TMPFILE" != "" ]; then
rm -f $TMPFILE
fi
exit -1
}
usage() {
echo "usage: gfp-translate [-h] [ --source DIRECTORY ] gfpmask"
exit 0
}
# Parse command-line arguments
while [ $# -gt 0 ]; do
case $1 in
--source)
SOURCE=$2
shift 2
;;
-h)
usage
;;
--help)
usage
;;
*)
GFPMASK=$1
shift
;;
esac
done
# Guess the kernel source directory if it's not set. Preference is in order of
# o current directory
# o /usr/src/linux
if [ "$SOURCE" = "" ]; then
if [ -r "/usr/src/linux/Makefile" ]; then
SOURCE=/usr/src/linux
fi
if [ -r "`pwd`/Makefile" ]; then
SOURCE=`pwd`
fi
fi
# Confirm that a source directory exists
if [ ! -r "$SOURCE/Makefile" ]; then
die "Could not locate kernel source directory or it is invalid"
fi
# Confirm that a GFP mask has been specified
if [ "$GFPMASK" = "none" ]; then
usage
fi
# Extract GFP flags from the kernel source
TMPFILE=`mktemp -t gfptranslate-XXXXXX` || exit 1
grep -q ___GFP $SOURCE/include/linux/gfp.h
if [ $? -eq 0 ]; then
grep "^#define ___GFP" $SOURCE/include/linux/gfp.h | sed -e 's/u$//' | grep -v GFP_BITS > $TMPFILE
else
grep "^#define __GFP" $SOURCE/include/linux/gfp.h | sed -e 's/(__force gfp_t)//' | sed -e 's/u)/)/' | grep -v GFP_BITS | sed -e 's/)\//) \//' > $TMPFILE
fi
# Parse the flags
IFS="
"
echo Source: $SOURCE
echo Parsing: $GFPMASK
for LINE in `cat $TMPFILE`; do
MASK=`echo $LINE | awk '{print $3}'`
if [ $(($GFPMASK&$MASK)) -ne 0 ]; then
echo $LINE
fi
done
rm -f $TMPFILE
exit 0
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