Re: [PATCH v3 2/3] commit-graph: fix buffer read-overflow
- From
Josh Steadmon <steadmon@google.com>
- Date
- Dec 10, 2018, 21:56 UTC
- Message-ID
- <20181210215649.GC37614@google.com>
- In-Reply-To
- <xmqqsgz74acm.fsf@gitster-ct.c.googlers.com>
On 2018.12.09 13:01, Junio C Hamano wrote:
Show 26 quoted lines
> Josh Steadmon <steadmon@google.com> writes:
>
> > diff --git a/t/t5318-commit-graph.sh b/t/t5318-commit-graph.sh
> > index 5fe21db99f..5b6b44b78e 100755
> > --- a/t/t5318-commit-graph.sh
> > +++ b/t/t5318-commit-graph.sh
> > @@ -366,24 +366,30 @@ GRAPH_OCTOPUS_DATA_OFFSET=$(($GRAPH_COMMIT_DATA_OFFSET + \
> > GRAPH_BYTE_OCTOPUS=$(($GRAPH_OCTOPUS_DATA_OFFSET + 4))
> > GRAPH_BYTE_FOOTER=$(($GRAPH_OCTOPUS_DATA_OFFSET + 4 * $NUM_OCTOPUS_EDGES))
> >
> > -# usage: corrupt_graph_and_verify <position> <data> <string>
> > +# usage: corrupt_graph_and_verify <position> <data> <string> [<zero_pos>]
> > # Manipulates the commit-graph file at the position
> > -# by inserting the data, then runs 'git commit-graph verify'
> > +# by inserting the data, optionally zeroing the file
> > +# starting at <zero_pos>, then runs 'git commit-graph verify'
> > # and places the output in the file 'err'. Test 'err' for
> > # the given string.
> > corrupt_graph_and_verify() {
> > pos=$1
> > data="${2:-\0}"
> > grepstr=$3
> > + orig_size=$(stat --format=%s $objdir/info/commit-graph)
>
> "stat(1)" is not so portable, so you'll get complaints from minority
> platform users later. So is "truncate(1)".Ack, thanks for the catch. I have a workaround for stat in the form of "wc -c", and for truncate with a combination of dd and /dev/zero. However, I'm finding conflicting information about whether or not /dev/zero exists on macOS. At the least, it sounds like it might not work on very old versions. Would this be acceptable, or should I add a new test function to do this?
Show 26 quoted lines
> > + zero_pos=${4:-${orig_size}}
> > cd "$TRASH_DIRECTORY/full" &&
> > test_when_finished mv commit-graph-backup $objdir/info/commit-graph &&
> > cp $objdir/info/commit-graph commit-graph-backup &&
> > printf "$data" | dd of="$objdir/info/commit-graph" bs=1 seek="$pos" conv=notrunc &&
> > + truncate --size=$zero_pos $objdir/info/commit-graph &&
> > + truncate --size=$orig_size $objdir/info/commit-graph &&
> > test_must_fail git commit-graph verify 2>test_err &&
> > grep -v "^+" test_err >err
> > test_i18ngrep "$grepstr" err
> > }
> >
> > +
> > test_expect_success 'detect bad signature' '
> > corrupt_graph_and_verify 0 "\0" \
> > "graph signature"
> > @@ -484,6 +490,11 @@ test_expect_success 'detect invalid checksum hash' '
> > "incorrect checksum"
> > '
> >
> > +test_expect_success 'detect incorrect chunk count' '
> > + corrupt_graph_and_verify $GRAPH_BYTE_CHUNK_COUNT "\xff" \
>
> Implementations of printf(1) may not grok "\xff" as a valid
> representation of "\377". The shell built-in of dash(1) for example
> would not work with this.Ack, will fix in V4. Thanks.
Show 6 quoted lines
> > + "chunk lookup table entry missing" $GRAPH_CHUNK_LOOKUP_OFFSET > > +' > > + > > test_expect_success 'git fsck (checks commit-graph)' ' > > cd "$TRASH_DIRECTORY/full" && > > git fsck &&