Add a check to prevent max_children from being 0, which may cause potential divide-by-zero. #1975

mugitya03 · 2025-05-23T01:36:55Z

gitgitgadget-git · 2025-05-23T01:37:44Z

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gitgitgadget-git · 2025-05-23T01:37:45Z

There are issues in commit beebfb5:
Add a check to prevent max_children from being 0. In fetch_multiple and fetch_submodules, multiple is stored in opt.process and later used as a divisor in function pp_collect_finished, creating a potential divide-by-zero if it remains zero.
Commit checks stopped - the message is too short
First line of commit message is too long (> 76 columns)
Commit not signed off

dscho · 2025-05-23T04:36:12Z

/allow

gitgitgadget-git · 2025-05-23T04:37:48Z

User mugitya03 is now allowed to use GitGitGadget.

WARNING: mugitya03 has no public email address set on GitHub; GitGitGadget needs an email address to Cc: you on your contribution, so that you receive any feedback on the Git mailing list. Go to https://github.com/settings/profile to make your preferred email public to let GitGitGadget know which email address to use.

mugitya03 · 2025-05-23T15:05:42Z

/submit

gitgitgadget-git · 2025-05-23T15:06:19Z

Error: Could not determine full name of mugitya03

mugitya03 · 2025-05-23T15:08:28Z

/submit

gitgitgadget-git · 2025-05-23T15:09:31Z

There are issues in commit beebfb5:
Add a check to prevent max_children from being 0. In fetch_multiple and fetch_submodules, multiple is stored in opt.process and later used as a divisor in function pp_collect_finished, creating a potential divide-by-zero if it remains zero.
Commit checks stopped - the message is too short
First line of commit message is too long (> 76 columns)
Commit not signed off

mugitya03 · 2025-05-23T16:15:46Z

/submit

gitgitgadget-git · 2025-05-23T16:16:13Z

There are issues in commit b718ef5:
Add a check to prevent max_children from being 0.
The first line must be separated from the rest by an empty line
Lines in the body of the commit messages should be wrapped between 60 and 76 characters.
Indented lines, and lines without whitespace, are exempt

gitgitgadget-git · 2025-05-23T16:16:58Z

There are issues in commit b718ef5:
Add a check to prevent max_children from being 0.
The first line must be separated from the rest by an empty line
Lines in the body of the commit messages should be wrapped between 60 and 76 characters.
Indented lines, and lines without whitespace, are exempt

In function fetch_multiple and fetch_submodules, `multiple` is stored in `opt.process` and later used as a divisor in function `pp_collect_finished`, creating a potential divide-by-zero if it remains zero. Signed-off-by: Alex Guo <[email protected]>

mugitya03 · 2025-05-23T16:19:47Z

/submit

gitgitgadget-git · 2025-05-23T16:20:50Z

Submitted as [email protected]

To fetch this version into FETCH_HEAD:

git fetch https://github.com/gitgitgadget/git/ pr-git-1975/mugitya03/int2-v1

To fetch this version to local tag pr-git-1975/mugitya03/int2-v1:

git fetch --no-tags https://github.com/gitgitgadget/git/ tag pr-git-1975/mugitya03/int2-v1

gitgitgadget-git · 2025-05-23T19:33:46Z

On the Git mailing list, Junio C Hamano wrote (reply to this):

"Alex via GitGitGadget" <[email protected]> writes:

> From: jinyaoguo <[email protected]>

This name (i.e. the author ident when you do "git comimt") ...

>
> In function fetch_multiple and fetch_submodules, `multiple` is
> stored in `opt.process` and later used as a divisor in function
> `pp_collect_finished`, creating a potential divide-by-zero if it
> remains zero.
>
> Signed-off-by: Alex Guo <[email protected]>

... must match the name used here you sign your work off as.

Unless you are forwarding a patch that is signed-off by somebody
else, in which case, their sign-off comes first and then yours.

> diff --git a/builtin/fetch.c b/builtin/fetch.c
> index cda6eaf1fd6..b668187627a 100644
> --- a/builtin/fetch.c
> +++ b/builtin/fetch.c
> @@ -2591,7 +2591,7 @@ int cmd_fetch(int argc,
>  			die(_("--stdin can only be used when fetching "
>  			      "from one remote"));
>  
> -		if (max_children < 0)
> +		if (max_children <= 0)
>  			max_children = config.parallel;
>  
>  		/* TODO should this also die if we have a previous partial-clone? */
> @@ -2613,9 +2613,9 @@ int cmd_fetch(int argc,
>  		struct strvec options = STRVEC_INIT;
>  		int max_children = max_jobs;
>  
> -		if (max_children < 0)
> +		if (max_children <= 0)
>  			max_children = config.submodule_fetch_jobs;
> -		if (max_children < 0)
> +		if (max_children <= 0)
>  			max_children = config.parallel;
>  
>  		add_options_to_argv(&options, &config);
>
> base-commit: 8613c2bb6cd16ef530dc5dd74d3b818a1ccbf1c0

I think you may have identified the right problem to fix, but I do
not know if the solution is correct.

If max_children can be 0 at this point due to loose parsing of the
end-user input, the config.parallel or config.submodule_fetch_jobs
configuration variables may be set to 0 due to the same kind of
loose parsing.

The command line parser parses -j0 as max_jobs==0 and then calls
online_cpus() to use.  If the function returned 0 on a platform
whose online_cpus() implementation is buggy, max_children may be
initialized to 0 there.  If fetch.parallel is given 0 by the user,
config.parallel gets value from online_cpus(), so it has the same
problem.  submodule.fetchjobs has exactly the same issue in
submodule-config.c::parse_submodule_fetchjobs().

But otherwise, I see no plausible way to have max_children to be 0
here.

And if we want to protect a buggy online_cpus() that returns 0 or
negative, which probably is a good thing to do anyway, perhaps we
should do so at the source of the issue, perhaps like the attached
patch.

Or if you are trying to be defensive to withstand the change to
other parts of the code that may affect max_children coming into
this function, I think it is better to add

	if (max_children <= 0)
		max_children = 1;

before we enter the trace2_region that calls fetch_multiple() and
fetch_submodules().

Hmm?

 thread-utils.c | 9 ++++++---
 1 file changed, 6 insertions(+), 3 deletions(-)

diff --git c/thread-utils.c w/thread-utils.c
index 1f89ffab4c..a5d644bb38 100644
--- c/thread-utils.c
+++ w/thread-utils.c
@@ -36,7 +36,8 @@ int online_cpus(void)
 #elif defined(hpux) || defined(__hpux) || defined(_hpux)
 	struct pst_dynamic psd;

-	if (!pstat_getdynamic(&psd, sizeof(psd), (size_t)1, 0))
+	if (!pstat_getdynamic(&psd, sizeof(psd), (size_t)1, 0) &&
+	    0 < psd.psd_proc_cnt)
 		return (int)psd.psd_proc_cnt;
 #elif defined(HAVE_BSD_SYSCTL) && defined(HW_NCPU)
 	int mib[2];
@@ -47,12 +48,14 @@ int online_cpus(void)
 #  ifdef HW_AVAILCPU
 	mib[1] = HW_AVAILCPU;
 	len = sizeof(cpucount);
-	if (!sysctl(mib, 2, &cpucount, &len, NULL, 0))
+	if (!sysctl(mib, 2, &cpucount, &len, NULL, 0) &&
+	    0 < cpucount)
 		return cpucount;
 #  endif /* HW_AVAILCPU */
 	mib[1] = HW_NCPU;
 	len = sizeof(cpucount);
-	if (!sysctl(mib, 2, &cpucount, &len, NULL, 0))
+	if (!sysctl(mib, 2, &cpucount, &len, NULL, 0) &&
+	    0 < cpucount)
 		return cpucount;
 #endif /* defined(HAVE_BSD_SYSCTL) && defined(HW_NCPU) */

gitgitgadget-git · 2025-05-25T15:22:27Z

On the Git mailing list, Jinyao Guo wrote (reply to this):

"Alex via GitGitGadget" <[email protected]> writes:

> From: jinyaoguo <[email protected]>

This name (i.e. the author ident when you do "git comimt") ...

>
> In function fetch_multiple and fetch_submodules, `multiple` is
> stored in `opt.process` and later used as a divisor in function
> `pp_collect_finished`, creating a potential divide-by-zero if it
> remains zero.
>
> Signed-off-by: Alex Guo <[email protected]>

... must match the name used here you sign your work off as.

Unless you are forwarding a patch that is signed-off by somebody
else, in which case, their sign-off comes first and then yours.

> diff --git a/builtin/fetch.c b/builtin/fetch.c
> index cda6eaf1fd6..b668187627a 100644
> --- a/builtin/fetch.c
> +++ b/builtin/fetch.c
> @@ -2591,7 +2591,7 @@ int cmd_fetch(int argc,
>                       die(_("--stdin can only be used when fetching "
>                             "from one remote"));
>
> -             if (max_children < 0)
> +             if (max_children <= 0)
>                       max_children = config.parallel;
>
>               /* TODO should this also die if we have a previous partial-clone? */
> @@ -2613,9 +2613,9 @@ int cmd_fetch(int argc,
>               struct strvec options = STRVEC_INIT;
>               int max_children = max_jobs;
>
> -             if (max_children < 0)
> +             if (max_children <= 0)
>                       max_children = config.submodule_fetch_jobs;
> -             if (max_children < 0)
> +             if (max_children <= 0)
>                       max_children = config.parallel;
>
>               add_options_to_argv(&options, &config);
>
> base-commit: 8613c2bb6cd16ef530dc5dd74d3b818a1ccbf1c0

I think you may have identified the right problem to fix, but I do
not know if the solution is correct.

If max_children can be 0 at this point due to loose parsing of the
end-user input, the config.parallel or config.submodule_fetch_jobs
configuration variables may be set to 0 due to the same kind of
loose parsing.

The command line parser parses -j0 as max_jobs==0 and then calls
online_cpus() to use.  If the function returned 0 on a platform
whose online_cpus() implementation is buggy, max_children may be
initialized to 0 there.  If fetch.parallel is given 0 by the user,
config.parallel gets value from online_cpus(), so it has the same
problem.  submodule.fetchjobs has exactly the same issue in
submodule-config.c::parse_submodule_fetchjobs().

But otherwise, I see no plausible way to have max_children to be 0
here.

And if we want to protect a buggy online_cpus() that returns 0 or
negative, which probably is a good thing to do anyway, perhaps we
should do so at the source of the issue, perhaps like the attached
patch.

Or if you are trying to be defensive to withstand the change to
other parts of the code that may affect max_children coming into
this function, I think it is better to add

        if (max_children <= 0)
                max_children = 1;

before we enter the trace2_region that calls fetch_multiple() and
fetch_submodules().

Hmm?

 thread-utils.c | 9 ++++++---
 1 file changed, 6 insertions(+), 3 deletions(-)

diff --git c/thread-utils.c w/thread-utils.c
index 1f89ffab4c..a5d644bb38 100644
--- c/thread-utils.c
+++ w/thread-utils.c
@@ -36,7 +36,8 @@ int online_cpus(void)
 #elif defined(hpux) || defined(__hpux) || defined(_hpux)
        struct pst_dynamic psd;

-       if (!pstat_getdynamic(&psd, sizeof(psd), (size_t)1, 0))
+       if (!pstat_getdynamic(&psd, sizeof(psd), (size_t)1, 0) &&
+           0 < psd.psd_proc_cnt)
                return (int)psd.psd_proc_cnt;
 #elif defined(HAVE_BSD_SYSCTL) && defined(HW_NCPU)
        int mib[2];
@@ -47,12 +48,14 @@ int online_cpus(void)
 #  ifdef HW_AVAILCPU
        mib[1] = HW_AVAILCPU;
        len = sizeof(cpucount);
-       if (!sysctl(mib, 2, &cpucount, &len, NULL, 0))
+       if (!sysctl(mib, 2, &cpucount, &len, NULL, 0) &&
+           0 < cpucount)
                return cpucount;
 #  endif /* HW_AVAILCPU */
        mib[1] = HW_NCPU;
        len = sizeof(cpucount);
-       if (!sysctl(mib, 2, &cpucount, &len, NULL, 0))
+       if (!sysctl(mib, 2, &cpucount, &len, NULL, 0) &&
+           0 < cpucount)
                return cpucount;
 #endif /* defined(HAVE_BSD_SYSCTL) && defined(HW_NCPU) */

The patch to `online_cpus` looks good to me. We can ensure online_cpus() will never return 0 or a negative value under any circumstance.

gitgitgadget-git · 2025-05-25T15:22:29Z

User Jinyao Guo <[email protected]> has been added to the cc: list.

gitgitgadget-git bot added the new user label May 23, 2025

jinyaoguo force-pushed the int2 branch from beebfb5 to b718ef5 Compare May 23, 2025 16:15

jinyaoguo force-pushed the int2 branch from b718ef5 to ee051c4 Compare May 23, 2025 16:19

Add a check to prevent max_children from being 0, which may cause potential divide-by-zero. #1975

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Add a check to prevent max_children from being 0, which may cause potential divide-by-zero. #1975

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