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Modify mountd.c so that it does not always malloc 4K for the map credentials.

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r362163 upgraded mountd so that it could handle MAX_NGROUPS
groups for the anonymous user credentials (the ones provided by
-maproot and -mapall exports options).
The problem is that this resulted in every export structure growing by
about 4Kbytes, because the cr_groups field went from 16->MAX_NGROUPS.

This patch fixes this by only including a small 32 element cr_groups in the
structure and then malloc()'ng cr_groups when a larger one is needed.
The value of SMALLNGROUPS is arbitrarily set to 32, assuming most users
used by -maproot or -mapall will be in <= 32 groups.

Reviewed by:	kib, freqlabs
Differential Revision:	https://reviews.freebsd.org/D26521
This commit is contained in:
Rick Macklem 2020-10-10 00:01:40 +00:00
parent c2c6fb90e0
commit 2ffad162f3
1 changed files with 44 additions and 16 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

60
usr.sbin/mountd/mountd.c
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@ -115,11 +115,15 @@ struct dirlist {
/*
* maproot/mapall credentials.
* cr_smallgrps can be used for a group list up to SMALLNGROUPS in size.
* Larger group lists are malloc'd/free'd.
*/
#define SMALLNGROUPS 32
struct expcred {
uid_t cr_uid;
int cr_ngroups;
gid_t cr_groups[NGROUPS_MAX + 1];
gid_t cr_smallgrps[SMALLNGROUPS];
gid_t *cr_groups;
};
struct exportlist {
@ -1514,6 +1518,7 @@ get_exportlist_one(int passno)
uint64_t exflags;
v4root_phase = 0;
anon.cr_groups = NULL;
dirhead = (struct dirlist *)NULL;
while (get_line()) {
if (debug)
@ -1527,6 +1532,7 @@ get_exportlist_one(int passno)
* Set defaults.
*/
has_host = FALSE;
anon.cr_groups = anon.cr_smallgrps;
anon.cr_uid = UID_NOBODY;
anon.cr_ngroups = 1;
anon.cr_groups[0] = GID_NOGROUP;
@ -1822,6 +1828,10 @@ get_exportlist_one(int passno)
free_dir(dirhead);
dirhead = (struct dirlist *)NULL;
}
if (anon.cr_groups != anon.cr_smallgrps) {
free(anon.cr_groups);
anon.cr_groups = NULL;
}
}
}
@ -2905,6 +2915,8 @@ free_exp(struct exportlist *ep)
grp = grp->gr_next;
free_grp(tgrp);
}
if (ep->ex_defanon.cr_groups != ep->ex_defanon.cr_smallgrps)
free(ep->ex_defanon.cr_groups);
free((caddr_t)ep);
}
@ -3457,14 +3469,17 @@ static void
parsecred(char *namelist, struct expcred *cr)
{
char *name;
int cnt;
int inpos;
char *names;
struct passwd *pw;
struct group *gr;
gid_t groups[NGROUPS_MAX + 1];
int ngroups;
/*
* Set up the unprivileged user.
*/
cr->cr_groups = cr->cr_smallgrps;
cr->cr_uid = UID_NOBODY;
cr->cr_groups[0] = GID_NOGROUP;
cr->cr_ngroups = 1;
@ -3487,24 +3502,28 @@ parsecred(char *namelist, struct expcred *cr)
return;
}
cr->cr_uid = pw->pw_uid;
cr->cr_ngroups = NGROUPS_MAX + 1;
if (getgrouplist(pw->pw_name, pw->pw_gid, cr->cr_groups,
&cr->cr_ngroups)) {
ngroups = NGROUPS_MAX + 1;
if (getgrouplist(pw->pw_name, pw->pw_gid, groups, &ngroups)) {
syslog(LOG_ERR, "too many groups");
cr->cr_ngroups = NGROUPS_MAX + 1;
ngroups = NGROUPS_MAX + 1;
}
/*
* Compress out duplicate.
*/
if (cr->cr_ngroups > 1 && cr->cr_groups[0] ==
cr->cr_groups[1]) {
for (cnt = 2; cnt < cr->cr_ngroups; cnt++)
cr->cr_groups[cnt - 1] = cr->cr_groups[cnt];
cr->cr_ngroups--;
}
if (cr->cr_ngroups > NGROUPS_MAX)
cr->cr_ngroups = NGROUPS_MAX;
if (ngroups > 1 && groups[0] == groups[1]) {
ngroups--;
inpos = 2;
} else
inpos = 1;
if (ngroups > NGROUPS_MAX)
ngroups = NGROUPS_MAX;
if (ngroups > SMALLNGROUPS)
cr->cr_groups = malloc(ngroups * sizeof(gid_t));
cr->cr_ngroups = ngroups;
cr->cr_groups[0] = groups[0];
memcpy(&cr->cr_groups[1], &groups[inpos], (ngroups - 1) *
sizeof(gid_t));
return;
}
/*
@ -3523,17 +3542,20 @@ parsecred(char *namelist, struct expcred *cr)
while (names != NULL && *names != '\0' && cr->cr_ngroups < NGROUPS_MAX) {
name = strsep_quote(&names, ":");
if (isdigit(*name) || *name == '-') {
cr->cr_groups[cr->cr_ngroups++] = atoi(name);
groups[cr->cr_ngroups++] = atoi(name);
} else {
if ((gr = getgrnam(name)) == NULL) {
syslog(LOG_ERR, "unknown group: %s", name);
continue;
}
cr->cr_groups[cr->cr_ngroups++] = gr->gr_gid;
groups[cr->cr_ngroups++] = gr->gr_gid;
}
}
if (names != NULL && *names != '\0' && cr->cr_ngroups == NGROUPS_MAX)
syslog(LOG_ERR, "too many groups");
if (cr->cr_ngroups > SMALLNGROUPS)
cr->cr_groups = malloc(cr->cr_ngroups * sizeof(gid_t));
memcpy(cr->cr_groups, groups, cr->cr_ngroups * sizeof(gid_t));
}
#define STRSIZ (MNTNAMLEN+MNTPATHLEN+50)
@ -3642,6 +3664,8 @@ free_grp(struct grouplist *grp)
if (grp->gr_ptr.gt_net.nt_name)
free(grp->gr_ptr.gt_net.nt_name);
}
if (grp->gr_anon.cr_groups != grp->gr_anon.cr_smallgrps)
free(grp->gr_anon.cr_groups);
free((caddr_t)grp);
}
@ -3860,6 +3884,10 @@ cp_cred(struct expcred *outcr, struct expcred *incr)
outcr->cr_uid = incr->cr_uid;
outcr->cr_ngroups = incr->cr_ngroups;
if (outcr->cr_ngroups > SMALLNGROUPS)
outcr->cr_groups = malloc(outcr->cr_ngroups * sizeof(gid_t));
else
outcr->cr_groups = outcr->cr_smallgrps;
memcpy(outcr->cr_groups, incr->cr_groups, incr->cr_ngroups *
sizeof(gid_t));
}