8000 promisor-remote: prevent recursive lazy-fetch during index-pack by ptarjan · Pull Request #2224 · git/git · GitHub
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promisor-remote: prevent recursive lazy-fetch during index-pack #2224

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promisor-remote: prevent recursive lazy-fetch during index-pack #2224

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7 changes: 7 additions & 0 deletions promisor-remote.c
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Original file line number Diff line number Diff line change
Expand Up @@ -42,6 +42,13 @@ static int fetch_objects(struct repository *repo,
child.in = -1;
if (repo != the_repository)
prepare_other_repo_env(&child.env, repo->gitdir);
/*
* Prevent the child's index-pack from recursing back into
* fetch_objects() when resolving REF_DELTA bases it does not
* have. With noop negotiation the server should never need
* to send such deltas, so a depth-2 fetch would not help.
*/
strvec_pushf(&child.env, "%s=1", NO_LAZY_FETCH_ENVIRONMENT);
strvec_pushl(&child.args, "-c", "fetch.negotiationAlgorithm=noop",
"fetch", remote_name, "--no-tags",
"--no-write-fetch-head", "--recurse-submodules=no",
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60 changes: 60 additions & 0 deletions t/t5616-partial-clone.sh
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Expand Up @@ -907,6 +907,66 @@ test_expect_success PERL_TEST_HELPERS 'tolerate server sending REF_DELTA against
! test -e "$HTTPD_ROOT_PATH/one-time-script"
'

test_expect_success PERL_TEST_HELPERS 'lazy-fetch of REF_DELTA with missing base does not recurse' '
SERVER="$HTTPD_DOCUMENT_ROOT_PATH/server" &&
rm -rf "$SERVER" repo &&
test_create_repo "$SERVER" &&
test_config -C "$SERVER" uploadpack.allowfilter 1 &&
test_config -C "$SERVER" uploadpack.allowanysha1inwant 1 &&

# Create a commit with 2 blobs to be used as delta base and content.
for i in $(test_seq 10)
do
echo "this is a line" >>"$SERVER/foo.txt" &&
echo "this is another line" >>"$SERVER/bar.txt" || return 1
done &&
git -C "$SERVER" add foo.txt bar.txt &&
git -C "$SERVER" commit -m initial &&
BLOB_FOO=$(git -C "$SERVER" rev-parse HEAD:foo.txt) &&
BLOB_BAR=$(git -C "$SERVER" rev-parse HEAD:bar.txt) &&

# Partial clone with blob:none. The client has commits and
# trees but no blobs.
test_config -C "$SERVER" protocol.version 2 &&
git -c protocol.version=2 clone --no-checkout \
--filter=blob:none $HTTPD_URL/one_time_script/server repo &&

# Sanity check: client does not have either blob locally.
git -C repo rev-list --objects --ignore-missing \
-- $BLOB_FOO >objlist &&
test_line_count = 0 objlist &&

# Craft a thin pack where BLOB_FOO is a REF_DELTA against
# BLOB_BAR. Since the client has neither blob (blob:none
# filter), the delta base will be missing. This simulates a
# misbehaving server that sends REF_DELTA against an object
# the client does not have.
test-tool -C "$SERVER" pack-deltas --num-objects=1 >thin.pack <<-EOF &&
REF_DELTA $BLOB_FOO $BLOB_BAR
EOF

replace_packfile thin.pack &&

# Trigger a lazy fetch for BLOB_FOO. The child fetch spawned
# by fetch_objects() receives our crafted thin pack. Its
# index-pack encounters the missing delta base (BLOB_BAR) and
# tries to lazy-fetch it via promisor_remote_get_direct().
#
# With the fix: fetch_objects() propagates GIT_NO_LAZY_FETCH=1
# to the child, so the depth-2 fetch is blocked and we see the
# "lazy fetching disabled" warning. The object cannot be
# resolved, so cat-file fails.
#
# Without the fix: the depth-2 fetch would proceed, potentially
# recursing unboundedly with a persistently misbehaving server.
test_must_fail git -C repo -c protocol.version=2 \
cat-file -p $BLOB_FOO 2>err &&
test_grep "lazy fetching disabled" err &&

# Ensure that the one-time-script was used.
! test -e "$HTTPD_ROOT_PATH/one-time-script"
'

# DO NOT add non-httpd-specific tests here, because the last part of this
# test script is only executed when httpd is available and enabled.

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