[PATCH experimental-tests] erofs-utils: tests: test FUSE error handling on corrupted inodes

[Gao Xiang]

On 2026/3/30 12:28, Nithurshen wrote:
> This patch introduces a regression test (erofs/099) to verify that
> the FUSE daemon gracefully handles corrupted inodes without crashing
> or violating the FUSE protocol.
> 
> Recently, a bug was identified where erofs_read_inode_from_disk()
> would fail, but erofsfuse_getattr() lacked a return statement
> after sending an error reply. This caused a fall-through, sending
> a second reply via fuse_reply_attr() and triggering a libfuse
> segmentation fault.
> 
> To prevent future regressions, this test:
> 1. Creates a valid EROFS image.
> 2. Surgically corrupts the root inode (injecting random data at
>     offset 1152) while leaving the superblock intact so it mounts.
> 3. Mounts the image in the foreground to capture daemon stderr.
> 4. Runs 'stat' to trigger the inode read failure.
> 5. Evaluates the stderr log to ensure no segfaults, aborts, or
>     "multiple replies" warnings are emitted by libfuse.
> 
> Signed-off-by: Nithurshen <nithurshen.dev at gmail.com>
> ---
>   tests/Makefile.am   |  3 ++
>   tests/erofs/099     | 76 +++++++++++++++++++++++++++++++++++++++++++++
>   tests/erofs/099.out |  2 ++
>   3 files changed, 81 insertions(+)
>   create mode 100755 tests/erofs/099
>   create mode 100644 tests/erofs/099.out
> 
> diff --git a/tests/Makefile.am b/tests/Makefile.am
> index e376d6a..c0f117c 100644
> --- a/tests/Makefile.am
> +++ b/tests/Makefile.am
> @@ -122,6 +122,9 @@ TESTS += erofs/027
>   # 028 - test inode page cache sharing functionality
>   TESTS += erofs/028
>   
> +# 099 - test fuse error handling on truncated images
> +TESTS += erofs/099
> +
>   EXTRA_DIST = common/rc erofs
>   
>   clean-local: clean-local-check
> diff --git a/tests/erofs/099 b/tests/erofs/099
> new file mode 100755
> index 0000000..952bdbd
> --- /dev/null
> +++ b/tests/erofs/099
> @@ -0,0 +1,76 @@
> +#!/bin/sh
> +# SPDX-License-Identifier: GPL-2.0+
> +#
> +# Test FUSE daemon error handling on corrupted inodes (missing return fix)
> +#
> +seq=`basename $0`
> +seqres=$RESULT_DIR/$(echo $0 | awk '{print $((NF-1))"/"$NF}' FS="/")
> +
> +# get standard environment, filters and checks
> +. "${srcdir}/common/rc"
> +
> +cleanup()
> +{
> +	cd /
> +	rm -rf $tmp.*
> +	# Ensure we kill our background daemon if it's still alive
> +	[ -n "$fuse_pid" ] && kill -9 $fuse_pid 2>/dev/null
> +}
> +
> +# remove previous $seqres.full before test
> +rm -f $seqres.full
> +
> +# real QA test starts here
> +echo "QA output created by $seq"
> +
> +[ -z "$EROFSFUSE_PROG" ] && _notrun "erofsfuse is not available"
> +
> +if [ -z $SCRATCH_DEV ]; then
> +	SCRATCH_DEV=$tmp/erofs_$seq.img
> +	rm -f SCRATCH_DEV
> +fi
> +
> +localdir="$tmp/$seq"
> +rm -rf $localdir
> +mkdir -p $localdir
> +
> +echo "test data" > $localdir/testfile
> +
> +_scratch_mkfs $localdir >> $seqres.full 2>&1 || _fail "failed to mkfs"
> +
> +# Corrupt the root inode to force erofs_read_inode_from_disk to fail.
> +dd if=/dev/urandom of=$SCRATCH_DEV bs=1 seek=1152 count=1024 conv=notrunc >> $seqres.full 2>&1
> +
> +# Bypass _scratch_mount to run erofsfuse in the foreground (-f)
> +# This lets us capture libfuse's internal stderr warnings.
> +$EROFSFUSE_PROG -f $SCRATCH_DEV $SCRATCH_MNT > $tmp/fuse_err.log 2>&1 &

If this testcase is erofsfuse-specific, we should
check FSTYP="erofsfuse" instead, otherwise this
case should be skiped.

Otherwise if this test case can test the kernel
as well, we should make the kernel tested too.

Thanks,
Gao Xiang