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Tue, 07 May 2024 17:05:51 -0700 (PDT) Received: from [127.0.0.1] ([13.74.141.28]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-41f87b2653bsm2450145e9.4.2024.05.07.17.05.50 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 07 May 2024 17:05:50 -0700 (PDT) Message-Id: In-Reply-To: References: From: "Derrick Stolee via GitGitGadget" Date: Wed, 08 May 2024 00:05:49 +0000 Subject: [PATCH v3] scalar: avoid segfault in reconfigure --all Fcc: Sent Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Precedence: bulk X-Mailing-List: git@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 To: git@vger.kernel.org Cc: Patrick Steinhardt , Derrick Stolee , Derrick Stolee From: Derrick Stolee During the latest v2.45.0 update, 'scalar reconfigure --all' started to segfault on my machine. Breaking it down via the debugger, it was faulting on a NULL reference to the_hash_algo, which is a macro pointing to the_repository->hash_algo. In my case, this is due to one of my repositories having a detached HEAD, which requires get_oid_hex() to parse that the HEAD reference is valid. Another way to cause a failure is to use the "includeIf.onbranch" config key, which will lead to a BUG() statement. My first inclination was to try to refactor cmd_reconfigure() to execute 'git for-each-repo' instead of this loop. In addition to the difficulty of executing 'scalar reconfigure' within 'git for-each-repo', it would be difficult to perform the clean-up logic for non-existent repos if we relied on that child process. Instead, I chose to move the temporary repo to be within the loop and reinstate the_repository to its old value after we are done performing logic on the current array item. Add tests to t9210-scalar.sh to test 'scalar reconfigure --all' with multiple registered repos. There are two different ways that the old use of the_repository could trigger bugs. These issues are being solved independently to be more careful about the_repository being uninitialized, but the change in this patch around the use of the_repository is still a good safety precaution. Co-authored-by: Patrick Steinhardt Signed-off-by: Patrick Steinhardt Signed-off-by: Derrick Stolee --- scalar: avoid segfault in reconfigure --all Update 'scalar reconfigure --all' to be more careful with the_repository pointer, avoiding sudden halts in some scenarios. ------------------------------------------------------------------------ I noticed this while validating the v2.45.0 release (specifically the microsoft/git fork, but this applies to the core project). Thanks, Patrick, for digging in and finding the critical reasons why this issue can happen. Patrick ACKed the sign-off in v2. v3 includes an update to the commit message. Sorry that I missed this paragraph when updating for v2. -Stolee Published-As: https://github.com/gitgitgadget/git/releases/tag/pr-1724%2Fderrickstolee%2Fscalar-reconfigure-repo-handle-v3 Fetch-It-Via: git fetch https://github.com/gitgitgadget/git pr-1724/derrickstolee/scalar-reconfigure-repo-handle-v3 Pull-Request: https://github.com/gitgitgadget/git/pull/1724 Range-diff vs v2: 1: 5be703b6c70 ! 1: 00d101986f8 scalar: avoid segfault in reconfigure --all @@ Commit message faulting on a NULL reference to the_hash_algo, which is a macro pointing to the_repository->hash_algo. - This NULL reference appears to be due to the way the loop is abusing the - the_repository pointer, pointing it to a local repository struct after - discovering that the current directory is a valid Git repository. This - repo-swapping bit was in the original implementation from 4582676075 - (scalar: teach 'reconfigure' to optionally handle all registered - enlistments, 2021-12-03), but only recently started segfaulting while - trying to parse the HEAD reference. This also only happens on the - _second_ repository in the list, so does not reproduce if there is only - one registered repo. + In my case, this is due to one of my repositories having a detached HEAD, + which requires get_oid_hex() to parse that the HEAD reference is valid. + Another way to cause a failure is to use the "includeIf.onbranch" config + key, which will lead to a BUG() statement. My first inclination was to try to refactor cmd_reconfigure() to execute 'git for-each-repo' instead of this loop. In addition to the difficulty scalar.c | 10 +++++++--- t/t9210-scalar.sh | 38 ++++++++++++++++++++++++++++++++++++++ 2 files changed, 45 insertions(+), 3 deletions(-) diff --git a/scalar.c b/scalar.c index fb2940c2a00..7234049a1b8 100644 --- a/scalar.c +++ b/scalar.c @@ -645,7 +645,6 @@ static int cmd_reconfigure(int argc, const char **argv) }; struct string_list scalar_repos = STRING_LIST_INIT_DUP; int i, res = 0; - struct repository r = { NULL }; struct strbuf commondir = STRBUF_INIT, gitdir = STRBUF_INIT; argc = parse_options(argc, argv, NULL, options, @@ -665,6 +664,7 @@ static int cmd_reconfigure(int argc, const char **argv) for (i = 0; i < scalar_repos.nr; i++) { int succeeded = 0; + struct repository *old_repo, r = { NULL }; const char *dir = scalar_repos.items[i].string; strbuf_reset(&commondir); @@ -712,13 +712,17 @@ static int cmd_reconfigure(int argc, const char **argv) git_config_clear(); + if (repo_init(&r, gitdir.buf, commondir.buf)) + goto loop_end; + + old_repo = the_repository; the_repository = &r; - r.commondir = commondir.buf; - r.gitdir = gitdir.buf; if (set_recommended_config(1) >= 0) succeeded = 1; + the_repository = old_repo; + loop_end: if (!succeeded) { res = -1; diff --git a/t/t9210-scalar.sh b/t/t9210-scalar.sh index 428339e3427..a41b4fcc085 100755 --- a/t/t9210-scalar.sh +++ b/t/t9210-scalar.sh @@ -180,6 +180,44 @@ test_expect_success 'scalar reconfigure' ' test true = "$(git -C one/src config core.preloadIndex)" ' +test_expect_success 'scalar reconfigure --all with includeIf.onbranch' ' + repos="two three four" && + for num in $repos + do + git init $num/src && + scalar register $num/src && + git -C $num/src config includeif."onbranch:foo".path something && + git -C $num/src config core.preloadIndex false || return 1 + done && + + scalar reconfigure --all && + + for num in $repos + do + test true = "$(git -C $num/src config core.preloadIndex)" || return 1 + done +' + + test_expect_success 'scalar reconfigure --all with detached HEADs' ' + repos="two three four" && + for num in $repos + do + rm -rf $num/src && + git init $num/src && + scalar register $num/src && + git -C $num/src config core.preloadIndex false && + test_commit -C $num/src initial && + git -C $num/src switch --detach HEAD || return 1 + done && + + scalar reconfigure --all && + + for num in $repos + do + test true = "$(git -C $num/src config core.preloadIndex)" || return 1 + done +' + test_expect_success '`reconfigure -a` removes stale config entries' ' git init stale/src && scalar register stale && base-commit: e326e520101dcf43a0499c3adc2df7eca30add2d -- gitgitgadget