From: "Ævar Arnfjörð Bjarmason" <avarab@gmail.com>
To: Victoria Dye <vdye@github.com>
Cc: Victoria Dye via GitGitGadget <gitgitgadget@gmail.com>,
git@vger.kernel.org, derrickstolee@github.com,
johannes.schindelin@gmx.de
Subject: Re: [PATCH 3/7] builtin/bugreport.c: avoid size_t overflow
Date: Wed, 03 Aug 2022 14:25:23 +0200 [thread overview]
Message-ID: <220803.86tu6tfqvf.gmgdl@evledraar.gmail.com> (raw)
In-Reply-To: <9fdac51b-ff8c-9564-d349-a71e42708479@github.com>
On Tue, Aug 02 2022, Victoria Dye wrote:
> Ævar Arnfjörð Bjarmason wrote:
>>
>> On Mon, Aug 01 2022, Victoria Dye via GitGitGadget wrote:
>>
>>> From: Victoria Dye <vdye@github.com>
>>>
>>> Avoid size_t overflow when reporting the available disk space in
>>> 'get_disk_info' by casting the block size and available block count to
>>> 'uint64_t' before multiplying them. Without this change, 'st_mult' would
>>> (correctly) report size_t overflow on 32-bit systems at or exceeding 2^32
>>> bytes of available space.
>>>
>>> Signed-off-by: Victoria Dye <vdye@github.com>
>>> ---
>>> builtin/bugreport.c | 2 +-
>>> 1 file changed, 1 insertion(+), 1 deletion(-)
>>>
>>> diff --git a/builtin/bugreport.c b/builtin/bugreport.c
>>> index 35b1fc48bf1..720889a37ad 100644
>>> --- a/builtin/bugreport.c
>>> +++ b/builtin/bugreport.c
>>> @@ -258,7 +258,7 @@ static int get_disk_info(struct strbuf *out)
>>> }
>>>
>>> strbuf_addf(out, "Available space on '%s': ", buf.buf);
>>> - strbuf_humanise_bytes(out, st_mult(stat.f_bsize, stat.f_bavail));
>>> + strbuf_humanise_bytes(out, (uint64_t)stat.f_bsize * (uint64_t)stat.f_bavail);
>>
>> Doesn't this remove the overflow guard on 64 bit systems to support
>> those 32 bit systems?
>>
>
> It does, but the total disk space available on a system should be able to
> fit into a 64-bit integer. I considered adding an explicit
> 'unsigned_mult_overflows', but decided against it because it's almost
> certainly overkill for such an implausible edge case.
Yeah it's probably overkill, and maybe this is good as-is & we don't
need to worry here.
But that's quite different from what the patch says, it's not "avoid
size_t overflow" but e.g.:
bugreport.c: don't do size_t overflow check before casting to 32bit
It's a hassle to support the check on 32 bit systems, and we
don't think this is something we'll run into in practice [...]
Perhaps?
>> I also don't tthink it's correct that this would "correctly
>> report...". Before this we were simply assuming that "size_t" and
>> "unsigned long" & "fsblkcnt_t" would all yield the same thing.
>>
>
> The point I was making is that, if your 'size_t' is 32 bits, but you have
> more than ~4GB of disk space available on your system, the result of the
> multiplication will overflow 'size_t'. So, 'st_mult' failing because it
> detects an overflow is "correct", rather than e.g. a false positive.
I think it would be useful to document these assumptions in the commit
message, POSIX just says "blkcnt_t and off_t shall be signed integer
types", and "size_t shall be an unsigned integer type.".
Do other bits of the standard(s) that I've missed say that off_t's
signed type must be double the width of size_t's unsigned, or is it one
of those things that's not standardized but can be relied on in
practice?
We have a related assertion in 37ee680d9b9 (http.postbuffer: allow full
range of ssize_t values, 2017-04-11) (xcurl_off_t()). Perhaps you want
to do something similar to sanity check your assumptions here?
1. https://pubs.opengroup.org/onlinepubs/009604599/basedefs/sys/types.h.html
next prev parent reply other threads:[~2022-08-03 12:34 UTC|newest]
Thread overview: 94+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-08-01 21:14 [PATCH 0/7] Generalize 'scalar diagnose' into 'git bugreport --diagnose' Victoria Dye via GitGitGadget
2022-08-01 21:14 ` [PATCH 1/7] scalar: use "$GIT_UNZIP" in 'scalar diagnose' test Victoria Dye via GitGitGadget
2022-08-01 21:46 ` Junio C Hamano
2022-08-01 21:14 ` [PATCH 2/7] builtin/bugreport.c: create '--diagnose' option Victoria Dye via GitGitGadget
2022-08-01 22:16 ` Junio C Hamano
2022-08-02 15:40 ` Victoria Dye
2022-08-02 2:17 ` Ævar Arnfjörð Bjarmason
2022-08-01 21:14 ` [PATCH 3/7] builtin/bugreport.c: avoid size_t overflow Victoria Dye via GitGitGadget
2022-08-01 22:18 ` Junio C Hamano
2022-08-02 16:26 ` Victoria Dye
2022-08-02 20:51 ` Junio C Hamano
2022-08-02 2:03 ` Ævar Arnfjörð Bjarmason
2022-08-02 16:26 ` Victoria Dye
2022-08-03 12:25 ` Ævar Arnfjörð Bjarmason [this message]
2022-08-01 21:14 ` [PATCH 4/7] builtin/bugreport.c: add directory to archiver more gently Victoria Dye via GitGitGadget
2022-08-01 22:22 ` Junio C Hamano
2022-08-02 15:43 ` Victoria Dye
2022-08-01 21:14 ` [PATCH 5/7] builtin/bugreport.c: add '--no-report' option Victoria Dye via GitGitGadget
2022-08-01 22:31 ` Junio C Hamano
2022-08-02 19:46 ` Victoria Dye
2022-08-01 21:14 ` [PATCH 6/7] scalar: use 'git bugreport --diagnose' in 'scalar diagnose' Victoria Dye via GitGitGadget
2022-08-01 21:14 ` [PATCH 7/7] scalar: update technical doc roadmap Victoria Dye via GitGitGadget
2022-08-01 21:34 ` [PATCH 0/7] Generalize 'scalar diagnose' into 'git bugreport --diagnose' Junio C Hamano
2022-08-02 2:49 ` Ævar Arnfjörð Bjarmason
2022-08-02 19:48 ` Victoria Dye
2022-08-03 12:34 ` Ævar Arnfjörð Bjarmason
2022-08-04 1:45 ` [PATCH v2 00/10] Generalize 'scalar diagnose' into 'git diagnose' and " Victoria Dye via GitGitGadget
2022-08-04 1:45 ` [PATCH v2 01/10] scalar-diagnose: use "$GIT_UNZIP" in test Victoria Dye via GitGitGadget
2022-08-04 1:45 ` [PATCH v2 02/10] scalar-diagnose: avoid 32-bit overflow of size_t Victoria Dye via GitGitGadget
2022-08-04 1:45 ` [PATCH v2 03/10] scalar-diagnose: add directory to archiver more gently Victoria Dye via GitGitGadget
2022-08-04 6:19 ` Ævar Arnfjörð Bjarmason
2022-08-04 17:12 ` Junio C Hamano
2022-08-04 20:12 ` Ævar Arnfjörð Bjarmason
2022-08-04 21:09 ` Junio C Hamano
2022-08-04 1:45 ` [PATCH v2 04/10] scalar-diagnose: move 'get_disk_info()' to 'compat/' Victoria Dye via GitGitGadget
2022-08-04 1:45 ` [PATCH v2 05/10] scalar-diagnose: move functionality to common location Victoria Dye via GitGitGadget
2022-08-04 6:24 ` Ævar Arnfjörð Bjarmason
2022-08-04 1:45 ` [PATCH v2 06/10] builtin/diagnose.c: create 'git diagnose' builtin Victoria Dye via GitGitGadget
2022-08-04 6:27 ` Ævar Arnfjörð Bjarmason
2022-08-05 19:38 ` Derrick Stolee
2022-08-11 11:06 ` Ævar Arnfjörð Bjarmason
2022-08-05 19:11 ` Derrick Stolee
2022-08-04 1:45 ` [PATCH v2 07/10] builtin/diagnose.c: gate certain data behind '--all' Victoria Dye via GitGitGadget
2022-08-04 6:39 ` Ævar Arnfjörð Bjarmason
2022-08-04 1:45 ` [PATCH v2 08/10] builtin/bugreport.c: create '--diagnose' option Victoria Dye via GitGitGadget
2022-08-05 19:35 ` Derrick Stolee
2022-08-09 23:53 ` Victoria Dye
2022-08-10 12:52 ` Derrick Stolee
2022-08-10 16:13 ` Victoria Dye
2022-08-10 16:47 ` Derrick Stolee
2022-08-04 1:45 ` [PATCH v2 09/10] scalar-diagnose: use 'git diagnose --all' Victoria Dye via GitGitGadget
2022-08-04 6:54 ` Ævar Arnfjörð Bjarmason
2022-08-09 16:54 ` Victoria Dye
2022-08-04 1:45 ` [PATCH v2 10/10] scalar: update technical doc roadmap Victoria Dye via GitGitGadget
2022-08-04 17:22 ` [PATCH v2 00/10] Generalize 'scalar diagnose' into 'git diagnose' and 'git bugreport --diagnose' Junio C Hamano
2022-08-09 16:17 ` Victoria Dye
2022-08-09 16:50 ` Junio C Hamano
2022-08-10 23:34 ` [PATCH v3 00/11] " Victoria Dye via GitGitGadget
2022-08-10 23:34 ` [PATCH v3 01/11] scalar-diagnose: use "$GIT_UNZIP" in test Victoria Dye via GitGitGadget
2022-08-10 23:34 ` [PATCH v3 02/11] scalar-diagnose: avoid 32-bit overflow of size_t Victoria Dye via GitGitGadget
2022-08-10 23:34 ` [PATCH v3 03/11] scalar-diagnose: add directory to archiver more gently Victoria Dye via GitGitGadget
2022-08-10 23:34 ` [PATCH v3 04/11] scalar-diagnose: move 'get_disk_info()' to 'compat/' Victoria Dye via GitGitGadget
2022-08-10 23:34 ` [PATCH v3 05/11] scalar-diagnose: move functionality to common location Victoria Dye via GitGitGadget
2022-08-10 23:34 ` [PATCH v3 06/11] diagnose.c: add option to configure archive contents Victoria Dye via GitGitGadget
2022-08-11 0:16 ` Junio C Hamano
2022-08-12 17:00 ` Victoria Dye
2022-08-11 10:51 ` Ævar Arnfjörð Bjarmason
2022-08-11 15:43 ` Victoria Dye
2022-08-10 23:34 ` [PATCH v3 07/11] builtin/diagnose.c: create 'git diagnose' builtin Victoria Dye via GitGitGadget
2022-08-10 23:34 ` [PATCH v3 08/11] builtin/diagnose.c: add '--mode' option Victoria Dye via GitGitGadget
2022-08-10 23:34 ` [PATCH v3 09/11] builtin/bugreport.c: create '--diagnose' option Victoria Dye via GitGitGadget
2022-08-11 10:53 ` Ævar Arnfjörð Bjarmason
2022-08-11 15:40 ` Victoria Dye
2022-08-11 20:30 ` Ævar Arnfjörð Bjarmason
2022-08-10 23:34 ` [PATCH v3 10/11] scalar-diagnose: use 'git diagnose --mode=all' Victoria Dye via GitGitGadget
2022-08-10 23:34 ` [PATCH v3 11/11] scalar: update technical doc roadmap Victoria Dye via GitGitGadget
2022-08-12 20:10 ` [PATCH v4 00/11] Generalize 'scalar diagnose' into 'git diagnose' and 'git bugreport --diagnose' Victoria Dye via GitGitGadget
2022-08-12 20:10 ` [PATCH v4 01/11] scalar-diagnose: use "$GIT_UNZIP" in test Victoria Dye via GitGitGadget
2022-08-12 20:10 ` [PATCH v4 02/11] scalar-diagnose: avoid 32-bit overflow of size_t Victoria Dye via GitGitGadget
2022-08-12 20:10 ` [PATCH v4 03/11] scalar-diagnose: add directory to archiver more gently Victoria Dye via GitGitGadget
2022-08-12 20:10 ` [PATCH v4 04/11] scalar-diagnose: move 'get_disk_info()' to 'compat/' Victoria Dye via GitGitGadget
2022-08-12 20:10 ` [PATCH v4 05/11] scalar-diagnose: move functionality to common location Victoria Dye via GitGitGadget
2022-08-12 20:26 ` Junio C Hamano
2022-08-12 21:00 ` Victoria Dye
2022-08-12 21:20 ` Junio C Hamano
2022-08-12 20:10 ` [PATCH v4 06/11] diagnose.c: add option to configure archive contents Victoria Dye via GitGitGadget
2022-08-12 20:31 ` Junio C Hamano
2022-08-12 20:10 ` [PATCH v4 07/11] builtin/diagnose.c: create 'git diagnose' builtin Victoria Dye via GitGitGadget
2022-08-18 18:43 ` Ævar Arnfjörð Bjarmason
2022-08-18 19:12 ` Junio C Hamano
2022-08-12 20:10 ` [PATCH v4 08/11] builtin/diagnose.c: add '--mode' option Victoria Dye via GitGitGadget
2022-08-12 20:10 ` [PATCH v4 09/11] builtin/bugreport.c: create '--diagnose' option Victoria Dye via GitGitGadget
2022-08-12 20:10 ` [PATCH v4 10/11] scalar-diagnose: use 'git diagnose --mode=all' Victoria Dye via GitGitGadget
2022-08-12 20:10 ` [PATCH v4 11/11] scalar: update technical doc roadmap Victoria Dye via GitGitGadget
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