# [PATCH] bisect--helper: avoid segfault with bad syntax in start --term-.+ 6 messages from 2020-05-20 to 2020-05-24. Participants: Carlo Marcelo Arenas Belón, Junio C Hamano, Eric Sunshine, Christian Couder. Thread: https://gitlist.dev/t/53514 ## Carlo Marcelo Arenas Belón, 2020-05-20 19:52 Subject: [PATCH] bisect--helper: avoid segfault with bad syntax in start --term-.+ Message-ID: <20200520195214.62655-1-carenas@gmail.com> URL: https://gitlist.dev/e/20200520195214.62655-1-carenas%40gmail.com ``` 06f5608c14 (bisect--helper: `bisect_start` shell function partially in C, 2019-01-02) adds a lax parser for `git bisect start` which could result in a segfault under a bad syntax call. Detect if they are enough arguments left in the command line to use for --term-{old,good,new,bad} and throw the same syntax error the old shell script will show if not. While at it, remove and unnecessary (and incomplete) check for unknown arguments. Signed-off-by: Carlo Marcelo Arenas Belón --- builtin/bisect--helper.c | 7 +++++-- 1 file changed, 5 insertions(+), 2 deletions(-) diff --git a/builtin/bisect--helper.c b/builtin/bisect--helper.c index c1c40b516d..37db7d2afa 100644 --- a/builtin/bisect--helper.c +++ b/builtin/bisect--helper.c @@ -455,6 +455,8 @@ static int bisect_start(struct bisect_terms *terms, int no_checkout, no_checkout = 1; } else if (!strcmp(arg, "--term-good") || !strcmp(arg, "--term-old")) { + if (argc - i <= 1) + return error(_("'' is not a valid term")); must_write_terms = 1; free((void *) terms->term_good); terms->term_good = xstrdup(argv[++i]); @@ -465,6 +467,8 @@ static int bisect_start(struct bisect_terms *terms, int no_checkout, terms->term_good = xstrdup(arg); } else if (!strcmp(arg, "--term-bad") || !strcmp(arg, "--term-new")) { + if (argc - i <= 1) + return error(_("'' is not a valid term")); must_write_terms = 1; free((void *) terms->term_bad); terms->term_bad = xstrdup(argv[++i]); @@ -473,8 +477,7 @@ static int bisect_start(struct bisect_terms *terms, int no_checkout, must_write_terms = 1; free((void *) terms->term_bad); terms->term_bad = xstrdup(arg); - } else if (starts_with(arg, "--") && - !one_of(arg, "--term-good", "--term-bad", NULL)) { + } else if (starts_with(arg, "--")) { return error(_("unrecognized option: '%s'"), arg); } else { char *commit_id = xstrfmt("%s^{commit}", arg); -- 2.27.0.rc0.187.gede8c892b8 ``` ## Junio C Hamano, 2020-05-20 20:20 Subject: Re: [PATCH] bisect--helper: avoid segfault with bad syntax in start --term-.+ Message-ID: URL: https://gitlist.dev/e/xmqqimgquznj.fsf%40gitster.c.googlers.com In-Reply-To: <20200520195214.62655-1-carenas@gmail.com> ``` Carlo Marcelo Arenas Belón writes: > 06f5608c14 (bisect--helper: `bisect_start` shell function partially in C, > 2019-01-02) adds a lax parser for `git bisect start` which could result > in a segfault under a bad syntax call. > > Detect if they are enough arguments left in the command line to use for > --term-{old,good,new,bad} and throw the same syntax error the old shell > script will show if not. Thanks for a quick discovery and fix. The bug is more than a year old---I guess nobody uses custom bisect terms? > While at it, remove and unnecessary (and incomplete) check for unknown > arguments. > > Signed-off-by: Carlo Marcelo Arenas Belón > --- > builtin/bisect--helper.c | 7 +++++-- > 1 file changed, 5 insertions(+), 2 deletions(-) > > diff --git a/builtin/bisect--helper.c b/builtin/bisect--helper.c > index c1c40b516d..37db7d2afa 100644 > --- a/builtin/bisect--helper.c > +++ b/builtin/bisect--helper.c > @@ -455,6 +455,8 @@ static int bisect_start(struct bisect_terms *terms, int no_checkout, > no_checkout = 1; > } else if (!strcmp(arg, "--term-good") || > !strcmp(arg, "--term-old")) { > + if (argc - i <= 1) > + return error(_("'' is not a valid term")); > must_write_terms = 1; > free((void *) terms->term_good); > terms->term_good = xstrdup(argv[++i]); As the variable that counts up in the loop is "i", it is easier to make the condition about "i", not about "difference between argc and i", e.g. if (argc - 1 <= i) return error(...) i.e. "The variable 'i' approached from 0 toward argc, and it went past (argc - 1) already." I used "<=" so that "went past" is more obvious (i.e. imagine a number-line where things on the left hand side are smaller than things on the right hand side). I think incrementing 'i' upfront, once we know we want to read one more from argv[], may make it even easier to read: } else if (... this is about term-good or term-old ...) { i++; if (argc <= i) return error(... missing arg ...); ... terms->term_good = xstrdup(argv[i]); The same comment applies to the handling of bad/new. Thanks. ``` ## Eric Sunshine, 2020-05-20 22:25 Subject: Re: [PATCH] bisect--helper: avoid segfault with bad syntax in start --term-.+ Message-ID: URL: https://gitlist.dev/e/CAPig%2BcT4kv1D6O5XnaihTODnoGtVeDdDmsPLX2g380r4%2BYK51w%40mail.gmail.com In-Reply-To: <20200520195214.62655-1-carenas@gmail.com> ``` On Wed, May 20, 2020 at 3:52 PM Carlo Marcelo Arenas Belón wrote: > 06f5608c14 (bisect--helper: `bisect_start` shell function partially in C, > 2019-01-02) adds a lax parser for `git bisect start` which could result > in a segfault under a bad syntax call. > > Detect if they are enough arguments left in the command line to use for s/they/there/ > --term-{old,good,new,bad} and throw the same syntax error the old shell > script will show if not. > > While at it, remove and unnecessary (and incomplete) check for unknown s/and/an/ > arguments. > > Signed-off-by: Carlo Marcelo Arenas Belón ``` ## Carlo Marcelo Arenas Belón, 2020-05-20 23:26 Subject: [PATCH v2] bisect--helper: avoid segfault with bad syntax in `start --term-*` Message-ID: <20200520232627.30901-1-carenas@gmail.com> URL: https://gitlist.dev/e/20200520232627.30901-1-carenas%40gmail.com In-Reply-To: <20200520195214.62655-1-carenas@gmail.com> ``` 06f5608c14 (bisect--helper: `bisect_start` shell function partially in C, 2019-01-02) adds a lax parser for `git bisect start` which could result in a segfault under a bad syntax call for start with custom terms. Detect if there are enough arguments left in the command line to use for --term-{old,good,new,bad} and abort with the same syntax error the original implementation will show if not. While at it, remove an unnecessary (and incomplete) check for unknown arguments and make sure to add a test to avoid regressions. Signed-off-by: Carlo Marcelo Arenas Belón --- v2: * nicer implementation (per Junio) and description (per Eric) * add test cases builtin/bisect--helper.c | 13 +++++++++---- t/t6030-bisect-porcelain.sh | 2 ++ 2 files changed, 11 insertions(+), 4 deletions(-) diff --git a/builtin/bisect--helper.c b/builtin/bisect--helper.c index c1c40b516d..ec4996282e 100644 --- a/builtin/bisect--helper.c +++ b/builtin/bisect--helper.c @@ -455,9 +455,12 @@ static int bisect_start(struct bisect_terms *terms, int no_checkout, no_checkout = 1; } else if (!strcmp(arg, "--term-good") || !strcmp(arg, "--term-old")) { + i++; + if (argc <= i) + return error(_("'' is not a valid term")); must_write_terms = 1; free((void *) terms->term_good); - terms->term_good = xstrdup(argv[++i]); + terms->term_good = xstrdup(argv[i]); } else if (skip_prefix(arg, "--term-good=", &arg) || skip_prefix(arg, "--term-old=", &arg)) { must_write_terms = 1; @@ -465,16 +468,18 @@ static int bisect_start(struct bisect_terms *terms, int no_checkout, terms->term_good = xstrdup(arg); } else if (!strcmp(arg, "--term-bad") || !strcmp(arg, "--term-new")) { + i++; + if (argc <= i) + return error(_("'' is not a valid term")); must_write_terms = 1; free((void *) terms->term_bad); - terms->term_bad = xstrdup(argv[++i]); + terms->term_bad = xstrdup(argv[i]); } else if (skip_prefix(arg, "--term-bad=", &arg) || skip_prefix(arg, "--term-new=", &arg)) { must_write_terms = 1; free((void *) terms->term_bad); terms->term_bad = xstrdup(arg); - } else if (starts_with(arg, "--") && - !one_of(arg, "--term-good", "--term-bad", NULL)) { + } else if (starts_with(arg, "--")) { return error(_("unrecognized option: '%s'"), arg); } else { char *commit_id = xstrfmt("%s^{commit}", arg); diff --git a/t/t6030-bisect-porcelain.sh b/t/t6030-bisect-porcelain.sh index 821a0c88cf..f7ef15a384 100755 --- a/t/t6030-bisect-porcelain.sh +++ b/t/t6030-bisect-porcelain.sh @@ -859,7 +859,9 @@ test_expect_success 'bisect cannot mix terms' ' test_expect_success 'bisect terms rejects invalid terms' ' git bisect reset && + test_must_fail git bisect start --term-good && test_must_fail git bisect start --term-good invalid..term && + test_must_fail git bisect start --term-bad && test_must_fail git bisect terms --term-bad invalid..term && test_must_fail git bisect terms --term-good bad && test_must_fail git bisect terms --term-good old && -- 2.27.0.rc1.181.g8d5cacc8d1 ``` ## Christian Couder, 2020-05-22 15:49 Subject: Re: [PATCH v2] bisect--helper: avoid segfault with bad syntax in `start --term-*` Message-ID: URL: https://gitlist.dev/e/CAP8UFD1Oa6g4kj8GDhDC-3ry1eFyg-aD%2BJVDtfK1TkJKuL8v-Q%40mail.gmail.com In-Reply-To: <20200520232627.30901-1-carenas@gmail.com> ``` On Thu, May 21, 2020 at 1:31 AM Carlo Marcelo Arenas Belón wrote: > > 06f5608c14 (bisect--helper: `bisect_start` shell function partially in C, > 2019-01-02) adds a lax parser for `git bisect start` which could result > in a segfault under a bad syntax call for start with custom terms. > > Detect if there are enough arguments left in the command line to use for > --term-{old,good,new,bad} and abort with the same syntax error the original > implementation will show if not. > > While at it, remove an unnecessary (and incomplete) check for unknown > arguments and make sure to add a test to avoid regressions. This looks good to me! Thanks, Christian. ``` ## Junio C Hamano, 2020-05-24 16:00 Subject: Re: [PATCH v2] bisect--helper: avoid segfault with bad syntax in `start --term-*` Message-ID: URL: https://gitlist.dev/e/xmqqr1v9qq58.fsf%40gitster.c.googlers.com In-Reply-To: ``` Christian Couder writes: > On Thu, May 21, 2020 at 1:31 AM Carlo Marcelo Arenas Belón > wrote: >> >> 06f5608c14 (bisect--helper: `bisect_start` shell function partially in C, >> 2019-01-02) adds a lax parser for `git bisect start` which could result >> in a segfault under a bad syntax call for start with custom terms. >> >> Detect if there are enough arguments left in the command line to use for >> --term-{old,good,new,bad} and abort with the same syntax error the original >> implementation will show if not. >> >> While at it, remove an unnecessary (and incomplete) check for unknown >> arguments and make sure to add a test to avoid regressions. > > This looks good to me! Thanks, both. ```