Re: git: f80babf906b7 - main - kern_sysctl: Make name2oid() non-destructive to the name

Good job !

> On Sep 24, 2023, at 12:23 AM, Alexander Motin <mav@FreeBSD.org> wrote:
> 
> The branch main has been updated by mav:
> 
> URL: https://cgit.FreeBSD.org/src/commit/?id=f80babf906b7be51b2a031ef26525893c7bf4e31
> 
> commit f80babf906b7be51b2a031ef26525893c7bf4e31
> Author:     Alexander Motin <mav@FreeBSD.org>
> AuthorDate: 2023-09-23 16:13:46 +0000
> Commit:     Alexander Motin <mav@FreeBSD.org>
> CommitDate: 2023-09-23 16:13:46 +0000
> 
>    kern_sysctl: Make name2oid() non-destructive to the name
> 
>    It is not the first time I see it panicking while trying to modify
>    const memory.  Lets make it safer and easier to use.  While there,
>    mark few functions using it also const.
> 
>    MFC after:      10 days
> ---
> sys/kern/kern_sysctl.c | 34 +++++++++++++++++++++++++++-------
> 1 file changed, 27 insertions(+), 7 deletions(-)
> 
> diff --git a/sys/kern/kern_sysctl.c b/sys/kern/kern_sysctl.c
> index 780eb6099b07..a4bfe8e21aed 100644
> --- a/sys/kern/kern_sysctl.c
> +++ b/sys/kern/kern_sysctl.c
> @@ -127,7 +127,7 @@ static int	sysctl_remove_oid_locked(struct sysctl_oid *oidp, int del,
> 		    int recurse);
> static int	sysctl_old_kernel(struct sysctl_req *, const void *, size_t);
> static int	sysctl_new_kernel(struct sysctl_req *, void *, size_t);
> -static int	name2oid(char *, int *, int *, struct sysctl_oid **);
> +static int	name2oid(const char *, int *, int *, struct sysctl_oid **);
> 
> static struct sysctl_oid *
> sysctl_find_oidname(const char *name, struct sysctl_oid_list *list)
> @@ -143,6 +143,21 @@ sysctl_find_oidname(const char *name, struct sysctl_oid_list *list)
> 	return (NULL);
> }
> 
> +static struct sysctl_oid *
> +sysctl_find_oidnamelen(const char *name, size_t len,
> +    struct sysctl_oid_list *list)
> +{
> +	struct sysctl_oid *oidp;
> +
> +	SYSCTL_ASSERT_LOCKED();
> +	SYSCTL_FOREACH(oidp, list) {
> +		if (strncmp(oidp->oid_name, name, len) == 0 &&
> +		    oidp->oid_name[len] == '\0')
> +			return (oidp);
> +	}
> +	return (NULL);
> +}
> +
> /*
>  * Initialization of the MIB tree.
>  *
> @@ -978,7 +993,7 @@ SYSINIT(sysctl, SI_SUB_KMEM, SI_ORDER_FIRST, sysctl_register_all, NULL);
> 
> #ifdef VIMAGE
> static void
> -sysctl_setenv_vnet(void *arg __unused, char *name)
> +sysctl_setenv_vnet(void *arg __unused, const char *name)
> {
> 	struct sysctl_oid *oidp;
> 	int oid[CTL_MAXNAME];
> @@ -1001,7 +1016,7 @@ out:
> }
> 
> static void
> -sysctl_unsetenv_vnet(void *arg __unused, char *name)
> +sysctl_unsetenv_vnet(void *arg __unused, const char *name)
> {
> 	struct sysctl_oid *oidp;
> 	int oid[CTL_MAXNAME];
> @@ -1419,21 +1434,26 @@ static SYSCTL_NODE(_sysctl, CTL_SYSCTL_NEXTNOSKIP, nextnoskip, CTLFLAG_RD |
>     CTLFLAG_MPSAFE | CTLFLAG_CAPRD, sysctl_sysctl_next, "");
> 
> static int
> -name2oid(char *name, int *oid, int *len, struct sysctl_oid **oidpp)
> +name2oid(const char *name, int *oid, int *len, struct sysctl_oid **oidpp)
> {
> 	struct sysctl_oid *oidp;
> 	struct sysctl_oid_list *lsp = &sysctl__children;
> +	const char *n;
> 
> 	SYSCTL_ASSERT_LOCKED();
> 
> 	for (*len = 0; *len < CTL_MAXNAME;) {
> -		oidp = sysctl_find_oidname(strsep(&name, "."), lsp);
> +		n = strchrnul(name, '.');
> +		oidp = sysctl_find_oidnamelen(name, n - name, lsp);
> 		if (oidp == NULL)
> 			return (ENOENT);
> 		*oid++ = oidp->oid_number;
> 		(*len)++;
> 
> -		if (name == NULL || *name == '\0') {
> +		name = n;
> +		if (*name == '.')
> +			name++;
> +		if (*name == '\0') {
> 			if (oidpp)
> 				*oidpp = oidp;
> 			return (0);
> @@ -2999,7 +3019,7 @@ db_show_sysctl_all(int *oid, size_t len, int flags)
>  * Show a sysctl by its user facing string
>  */
> static int
> -db_sysctlbyname(char *name, int flags)
> +db_sysctlbyname(const char *name, int flags)
> {
> 	struct sysctl_oid *oidp;
> 	int oid[CTL_MAXNAME];