* [PATCH 1/2] rev-parse: demonstrate overflow of N for "foo^N" and "foo~N"
@ 2019-09-15 12:03 René Scharfe
2019-09-15 12:10 ` [PATCH 2/2] sha1-name: check for overflow of N in " René Scharfe
0 siblings, 1 reply; 4+ messages in thread
From: René Scharfe @ 2019-09-15 12:03 UTC (permalink / raw)
To: Git Mailing List; +Cc: Junio C Hamano
If the number gets too high for an int, weird things may happen, as
signed overflows are undefined. Add a test to show this; rev-parse
"sucessfully" interprets 100000000000000000000000000000000 to be the
same as 0, at least on x64 with GCC 9.2.1 and Clang 8.0.1, which is
obviously bogus.
Signed-off-by: René Scharfe <l.s.r@web.de>
---
t/t1506-rev-parse-diagnosis.sh | 8 ++++++++
1 file changed, 8 insertions(+)
diff --git a/t/t1506-rev-parse-diagnosis.sh b/t/t1506-rev-parse-diagnosis.sh
index 4ee009da66..5c4df47401 100755
--- a/t/t1506-rev-parse-diagnosis.sh
+++ b/t/t1506-rev-parse-diagnosis.sh
@@ -215,4 +215,12 @@ test_expect_success 'arg before dashdash must be a revision (ambiguous)' '
test_cmp expect actual
'
+test_expect_failure 'reject Nth parent if N is too high' '
+ test_must_fail git rev-parse HEAD^100000000000000000000000000000000
+'
+
+test_expect_failure 'reject Nth ancestor if N is too high' '
+ test_must_fail git rev-parse HEAD~100000000000000000000000000000000
+'
+
test_done
--
2.23.0
^ permalink raw reply related [flat|nested] 4+ messages in thread
* [PATCH 2/2] sha1-name: check for overflow of N in "foo^N" and "foo~N"
2019-09-15 12:03 [PATCH 1/2] rev-parse: demonstrate overflow of N for "foo^N" and "foo~N" René Scharfe
@ 2019-09-15 12:10 ` René Scharfe
2019-09-15 15:15 ` brian m. carlson
0 siblings, 1 reply; 4+ messages in thread
From: René Scharfe @ 2019-09-15 12:10 UTC (permalink / raw)
To: Git Mailing List; +Cc: Junio C Hamano
Reject values that don't fit into an int, as get_parent() and
get_nth_ancestor() cannot handle them. That's better than potentially
returning a random object.
If this restriction turns out to be too tight then we can switch to a
wider data type, but we'd still have to check for overflow.
Signed-off-by: René Scharfe <l.s.r@web.de>
---
sha1-name.c | 15 ++++++++++++---
t/t1506-rev-parse-diagnosis.sh | 4 ++--
2 files changed, 14 insertions(+), 5 deletions(-)
diff --git a/sha1-name.c b/sha1-name.c
index c665e3f96d..7a047e9e2b 100644
--- a/sha1-name.c
+++ b/sha1-name.c
@@ -1160,13 +1160,22 @@ static enum get_oid_result get_oid_1(struct repository *r,
}
if (has_suffix) {
- int num = 0;
+ unsigned int num = 0;
int len1 = cp - name;
cp++;
- while (cp < name + len)
- num = num * 10 + *cp++ - '0';
+ while (cp < name + len) {
+ unsigned int digit = *cp++ - '0';
+ if (unsigned_mult_overflows(num, 10))
+ return MISSING_OBJECT;
+ num *= 10;
+ if (unsigned_add_overflows(num, digit))
+ return MISSING_OBJECT;
+ num += digit;
+ }
if (!num && len1 == len - 1)
num = 1;
+ else if (num > INT_MAX)
+ return MISSING_OBJECT;
if (has_suffix == '^')
return get_parent(r, name, len1, oid, num);
/* else if (has_suffix == '~') -- goes without saying */
diff --git a/t/t1506-rev-parse-diagnosis.sh b/t/t1506-rev-parse-diagnosis.sh
index 5c4df47401..6a938b205b 100755
--- a/t/t1506-rev-parse-diagnosis.sh
+++ b/t/t1506-rev-parse-diagnosis.sh
@@ -215,11 +215,11 @@ test_expect_success 'arg before dashdash must be a revision (ambiguous)' '
test_cmp expect actual
'
-test_expect_failure 'reject Nth parent if N is too high' '
+test_expect_success 'reject Nth parent if N is too high' '
test_must_fail git rev-parse HEAD^100000000000000000000000000000000
'
-test_expect_failure 'reject Nth ancestor if N is too high' '
+test_expect_success 'reject Nth ancestor if N is too high' '
test_must_fail git rev-parse HEAD~100000000000000000000000000000000
'
--
2.23.0
^ permalink raw reply related [flat|nested] 4+ messages in thread
* Re: [PATCH 2/2] sha1-name: check for overflow of N in "foo^N" and "foo~N"
2019-09-15 12:10 ` [PATCH 2/2] sha1-name: check for overflow of N in " René Scharfe
@ 2019-09-15 15:15 ` brian m. carlson
2019-09-15 16:12 ` René Scharfe
0 siblings, 1 reply; 4+ messages in thread
From: brian m. carlson @ 2019-09-15 15:15 UTC (permalink / raw)
To: René Scharfe; +Cc: Git Mailing List, Junio C Hamano
[-- Attachment #1: Type: text/plain, Size: 1911 bytes --]
On 2019-09-15 at 12:10:28, René Scharfe wrote:
> Reject values that don't fit into an int, as get_parent() and
> get_nth_ancestor() cannot handle them. That's better than potentially
> returning a random object.
>
> If this restriction turns out to be too tight then we can switch to a
> wider data type, but we'd still have to check for overflow.
Certainly we want Git to perform as well as possible on large
repositories, but I doubt if it will scale to more than 2 billion
revisions, even with significant effort. I think this restriction
should be fine.
> diff --git a/sha1-name.c b/sha1-name.c
> index c665e3f96d..7a047e9e2b 100644
> --- a/sha1-name.c
> +++ b/sha1-name.c
> @@ -1160,13 +1160,22 @@ static enum get_oid_result get_oid_1(struct repository *r,
> }
>
> if (has_suffix) {
> - int num = 0;
> + unsigned int num = 0;
> int len1 = cp - name;
> cp++;
> - while (cp < name + len)
> - num = num * 10 + *cp++ - '0';
> + while (cp < name + len) {
> + unsigned int digit = *cp++ - '0';
> + if (unsigned_mult_overflows(num, 10))
> + return MISSING_OBJECT;
> + num *= 10;
> + if (unsigned_add_overflows(num, digit))
> + return MISSING_OBJECT;
I was worried whether these functions only handled size_t or if they
also handle unsigned int, but I checked and they seem to be fine for any
unsigned type.
> + num += digit;
> + }
> if (!num && len1 == len - 1)
> num = 1;
> + else if (num > INT_MAX)
> + return MISSING_OBJECT;
> if (has_suffix == '^')
> return get_parent(r, name, len1, oid, num);
> /* else if (has_suffix == '~') -- goes without saying */
This approach seems reasonable. I must admit some curiosity as to how
you discovered this issue, though. Did you have a cat assisting you in
typing revisions?
--
brian m. carlson: Houston, Texas, US
OpenPGP: https://keybase.io/bk2204
[-- Attachment #2: signature.asc --]
[-- Type: application/pgp-signature, Size: 868 bytes --]
^ permalink raw reply [flat|nested] 4+ messages in thread
* Re: [PATCH 2/2] sha1-name: check for overflow of N in "foo^N" and "foo~N"
2019-09-15 15:15 ` brian m. carlson
@ 2019-09-15 16:12 ` René Scharfe
0 siblings, 0 replies; 4+ messages in thread
From: René Scharfe @ 2019-09-15 16:12 UTC (permalink / raw)
To: brian m. carlson, Git Mailing List, Junio C Hamano
Am 15.09.19 um 17:15 schrieb brian m. carlson:
> This approach seems reasonable. I must admit some curiosity as to how
> you discovered this issue, though. Did you have a cat assisting you in
> typing revisions?
Found it by reading the code, but I'm not sure anymore what I was
actually looking for.
Would a fuzzer (or a cat) be able to catch that? The function is
happily eating extra digits -- it's not crashing for me.
René
^ permalink raw reply [flat|nested] 4+ messages in thread
end of thread, other threads:[~2019-09-15 16:12 UTC | newest]
Thread overview: 4+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2019-09-15 12:03 [PATCH 1/2] rev-parse: demonstrate overflow of N for "foo^N" and "foo~N" René Scharfe
2019-09-15 12:10 ` [PATCH 2/2] sha1-name: check for overflow of N in " René Scharfe
2019-09-15 15:15 ` brian m. carlson
2019-09-15 16:12 ` René Scharfe
Code repositories for project(s) associated with this public inbox
https://80x24.org/mirrors/git.git
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for read-only IMAP folder(s) and NNTP newsgroup(s).