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Revision a57b70519d1f7c53be98478623652738e5ac70d5 authored by Liam Howlett on 18 October 2022, 19:17:12 UTC, committed by Andrew Morton on 21 October 2022, 04:27:23 UTC 
mm/mmap: fix MAP_FIXED address return on VMA merge
 
mmap should return the start address of newly mapped area when successful.
On a successful merge of a VMA, the return address was changed and thus
was violating that expectation from userspace.

This is a restoration of functionality provided by 309d08d9b3a3
(mm/mmap.c: fix mmap return value when vma is merged after call_mmap()). 
For completeness of fixing MAP_FIXED, implement the comments from the
previous discussion to never update the address and fail if the address
changes.  Leaving the error as a WARN_ON() to avoid crashing the kernel.

Link: https://lkml.kernel.org/r/20221018191613.4133459-1-Liam.Howlett@oracle.com
Link: https://lore.kernel.org/all/Y06yk66SKxlrwwfb@lakrids/
Link: https://lore.kernel.org/all/20201203085350.22624-1-liuzixian4@huawei.com/
Fixes: 4dd1b84140c1 ("mm/mmap: use advanced maple tree API for mmap_region()")
Signed-off-by: Liam R. Howlett <Liam.Howlett@oracle.com>
Reported-by: Mark Rutland <mark.rutland@arm.com>
Cc: Liu Zixian <liuzixian4@huawei.com>
Cc: David Hildenbrand <david@redhat.com>
Cc: Jason Gunthorpe <jgg@nvidia.com>
Cc: Matthew Wilcox <willy@infradead.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
1 parent 1cd916d
Raw File
test_fortify.sh 
#!/bin/sh
# SPDX-License-Identifier: GPL-2.0-only
set -e

# Argument 1: Source file to build.
IN="$1"
shift
# Extract just the filename for error messages below.
FILE="${IN##*/}"
# Extract the function name for error messages below.
FUNC="${FILE#*-}"
FUNC="${FUNC%%-*}"
FUNC="${FUNC%%.*}"
# Extract the symbol to test for in build/symbol test below.
WANT="__${FILE%%-*}"

# Argument 2: Where to write the build log.
OUT="$1"
shift
TMP="${OUT}.tmp"

# Argument 3: Path to "nm" tool.
NM="$1"
shift

# Remaining arguments are: $(CC) $(c_flags)

# Clean up temporary file at exit.
__cleanup() {
	rm -f "$TMP"
}
trap __cleanup EXIT

# Function names in warnings are wrapped in backticks under UTF-8 locales.
# Run the commands with LANG=C so that grep output will not change.
export LANG=C

status=
# Attempt to build a source that is expected to fail with a specific warning.
if "$@" -Werror -c "$IN" -o "$OUT".o 2> "$TMP" ; then
	# If the build succeeds, either the test has failed or the
	# warning may only happen at link time (Clang). In that case,
	# make sure the expected symbol is unresolved in the symbol list.
	# If so, FORTIFY is working for this case.
	if ! $NM -A "$OUT".o | grep -m1 "\bU ${WANT}$" >>"$TMP" ; then
		status="warning: unsafe ${FUNC}() usage lacked '$WANT' symbol in $IN"
	fi
else
	# If the build failed, check for the warning in the stderr.
	# GCC:
	# ./include/linux/fortify-string.h:316:25: error: call to '__write_overflow_field' declared with attribute warning: detected write beyond size of field (1st parameter); maybe use struct_group()? [-Werror=attribute-warning]
	# Clang 14:
	# ./include/linux/fortify-string.h:316:4: error: call to __write_overflow_field declared with 'warning' attribute: detected write beyond size of field (1st parameter); maybe use struct_group()? [-Werror,-Wattribute-warning]
	if ! grep -Eq -m1 "error: call to .?\b${WANT}\b.?" "$TMP" ; then
		status="warning: unsafe ${FUNC}() usage lacked '$WANT' warning in $IN"
	fi
fi

if [ -n "$status" ]; then
	# Report on failure results, including compilation warnings.
	echo "$status" | tee "$OUT" >&2
else
	# Report on good results, and save any compilation output to log.
	echo "ok: unsafe ${FUNC}() usage correctly detected with '$WANT' in $IN" >"$OUT"
fi
cat "$TMP" >>"$OUT"
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