| Message ID | pull.1724.v2.git.1714874298859.gitgitgadget@gmail.com (mailing list archive) |
|---|---|
| State | Superseded |
| Headers | show |
| Series | [v2] scalar: avoid segfault in reconfigure --all | expand |
On Sun, May 05, 2024 at 01:58:18AM +0000, Derrick Stolee via GitGitGadget wrote: > From: Derrick Stolee <stolee@gmail.com> > > 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. > > 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. I think this explanation could use an update now that we have figured out the root cause likely being a detached HEAD, where `get_oid_hex()` will then access a NULL pointer. > 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 <ps@pks.im> > Signed-off-by: Patrick Steinhardt <ps@pks.im> > Signed-off-by: Derrick Stolee <stolee@gmail.com> > --- > 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. I've included Patrick's test cases and given him > co-authorship. I forged his sign-off, so could you please ACK that > sign-off, Patrick? > > -Stolee Other than the above nit regarding the root cause analysis this patch looks good to me, and I'm fine with the forged SOB. Thanks! Patrick
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 &&