From: Junio C Hamano Date: Wed, 14 Oct 2026 21:44:51 GMT Subject: Re: [PATCH 5/5] date: avoid overflow in approxidate relative-time multiplication Message-ID: In-Reply-To: "Johannes Schindelin via GitGitGadget" writes: > On platforms where `time_t` is unsigned (and where the pre-processor > allows us to determine this fact), reject counts that are too large and > report a parse error. Narrowing them first could otherwise produce > negative or truncated values that become bogus offsets. Leave signed > `time_t` count parsing unchanged. Does this mean that "git log -p" in a project that were made on reasonably sized platforms and then cloned to my box may cause the history traversal to stop with an error when a commit has author or committer timestamp that would not fit the time_t on my box? It would have been horrible regression than showing the entire history with patches with bogus timestamp if it were the case. But I do not think that is what happens. approxidate_careful() is only used to parse input by local user (e.g., "git commit --date="...", "git log @{...}"), and the changes in this patch would not affect behaviours of other uses of timestamps, so we are safe. > Signed-off-by: Johannes Schindelin > --- > date.c | 26 ++++++++++++++++++++++++-- > 1 file changed, 24 insertions(+), 2 deletions(-) > > diff --git a/date.c b/date.c > index 014065b419..0d65804d2f 100644 > --- a/date.c > +++ b/date.c > @@ -1298,7 +1298,18 @@ static const char *approxidate_alpha(const char *date, struct tm *tm, struct tm > while (tl->type) { > size_t len = strlen(tl->type); > if (match_string(date, tl->type) >= len-1) { > - update_tm(tm, now, tl->length * *num); > + time_t length = tl->length, num_t = *num; > + time_t seconds; > +#ifndef is_unsigned_type > + seconds = length * num_t; > +#else > + time_t max_val = is_unsigned_type(length) > + ? maximum_unsigned_value_of_type(length) > + : maximum_signed_value_of_type(length); > + seconds = mult_overflows(length, num_t) > + ? max_val : length * num_t; > +#endif > + update_tm(tm, now, seconds); > *num = 0; > *touched = 1; > return end; > @@ -1368,8 +1379,15 @@ static const char *approxidate_digit(const char *date, struct tm *tm, int *num, > } > > /* Accept zero-padding only for small numbers ("Dec 02", never "Dec 0002") */ > - if (date[0] != '0' || end - date <= 2) > + if (date[0] != '0' || end - date <= 2) { > +#ifdef is_unsigned_type > + if (is_unsigned_type((time_t)0) && > + (number > INT_MAX || > + number > maximum_unsigned_value_of_type((time_t)0))) > + return NULL; > +#endif > *num = number; > + } > return end; > } > > @@ -1398,6 +1416,10 @@ static timestamp_t approxidate_str(const char *date, > if (isdigit(c)) { > pending_number(&tm, &number); > date = approxidate_digit(date-1, &tm, &number, time_sec); > + if (!date) { > + *error_ret = 1; > + return 0; > + } > touched = 1; > continue; > }