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params: cleanup sysfs allocation

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commit 63662139e5 attempted to patch a
leak (which would only happen on OOM, ie. never), but it didn't quite
work.

This rewrites the code to be as simple as possible.  add_sysfs_param()
adds a parameter.  If it fails, it's the caller's responsibility to
clean up the parameters which already exist.

The kzalloc-then-always-krealloc pattern is perhaps overly simplistic,
but this code has clearly confused people.  It worked on me...

Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
This commit is contained in:
Rusty Russell
2014-11-10 09:32:29 +10:30
parent 6da0b56515
commit 18eb74fa94
1 changed files with 44 additions and 51 deletions
Download Patch File Download Diff File Expand all files Collapse all files
kernel/params.c
+44 -51
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@@ -603,74 +603,65 @@ static __modinit int add_sysfs_param(struct module_kobject *mk,
const struct kernel_param *kp, const struct kernel_param *kp,
const char *name) const char *name)
{ {
struct module_param_attrs *new; struct module_param_attrs *new_mp;
struct attribute **attrs; struct attribute **new_attrs;
int err, num; unsigned int i;
/* We don't bother calling this with invisible parameters. */ /* We don't bother calling this with invisible parameters. */
BUG_ON(!kp->perm); BUG_ON(!kp->perm);
if (!mk->mp) { if (!mk->mp) {
num = 0; /* First allocation. */
attrs = NULL; mk->mp = kzalloc(sizeof(*mk->mp), GFP_KERNEL);
} else { if (!mk->mp)
num = mk->mp->num; return -ENOMEM;
attrs = mk->mp->grp.attrs; mk->mp->grp.name = "parameters";
/* NULL-terminated attribute array. */
mk->mp->grp.attrs = kzalloc(sizeof(mk->mp->grp.attrs[0]),
GFP_KERNEL);
/* Caller will cleanup via free_module_param_attrs */
if (!mk->mp->grp.attrs)
return -ENOMEM;
} }
/* Enlarge. */ /* Enlarge allocations. */
new = krealloc(mk->mp, new_mp = krealloc(mk->mp,
sizeof(*mk->mp) + sizeof(mk->mp->attrs[0]) * (num+1), sizeof(*mk->mp) +
GFP_KERNEL); sizeof(mk->mp->attrs[0]) * (mk->mp->num + 1),
if (!new) { GFP_KERNEL);
kfree(attrs); if (!new_mp)
err = -ENOMEM; return -ENOMEM;
goto fail; mk->mp = new_mp;
}
/* Despite looking like the typical realloc() bug, this is safe.
* We *want* the old 'attrs' to be freed either way, and we'll store
* the new one in the success case. */
attrs = krealloc(attrs, sizeof(new->grp.attrs[0])*(num+2), GFP_KERNEL);
if (!attrs) {
err = -ENOMEM;
goto fail_free_new;
}
/* Sysfs wants everything zeroed. */ /* Extra pointer for NULL terminator */
memset(new, 0, sizeof(*new)); new_attrs = krealloc(mk->mp->grp.attrs,
memset(&new->attrs[num], 0, sizeof(new->attrs[num])); sizeof(mk->mp->grp.attrs[0]) * (mk->mp->num + 2),
memset(&attrs[num], 0, sizeof(attrs[num])); GFP_KERNEL);
new->grp.name = "parameters"; if (!new_attrs)
new->grp.attrs = attrs; return -ENOMEM;
mk->mp->grp.attrs = new_attrs;
/* Tack new one on the end. */ /* Tack new one on the end. */
sysfs_attr_init(&new->attrs[num].mattr.attr); sysfs_attr_init(&mk->mp->attrs[mk->mp->num].mattr.attr);
new->attrs[num].param = kp; mk->mp->attrs[mk->mp->num].param = kp;
new->attrs[num].mattr.show = param_attr_show; mk->mp->attrs[mk->mp->num].mattr.show = param_attr_show;
new->attrs[num].mattr.store = param_attr_store; mk->mp->attrs[mk->mp->num].mattr.store = param_attr_store;
new->attrs[num].mattr.attr.name = (char *)name; mk->mp->attrs[mk->mp->num].mattr.attr.name = (char *)name;
new->attrs[num].mattr.attr.mode = kp->perm; mk->mp->attrs[mk->mp->num].mattr.attr.mode = kp->perm;
new->num = num+1; mk->mp->num++;
/* Fix up all the pointers, since krealloc can move us */ /* Fix up all the pointers, since krealloc can move us */
for (num = 0; num < new->num; num++) for (i = 0; i < mk->mp->num; i++)
new->grp.attrs[num] = &new->attrs[num].mattr.attr; mk->mp->grp.attrs[i] = &mk->mp->attrs[i].mattr.attr;
new->grp.attrs[num] = NULL; mk->mp->grp.attrs[mk->mp->num] = NULL;
mk->mp = new;
return 0; return 0;
fail_free_new:
kfree(new);
fail:
mk->mp = NULL;
return err;
} }
#ifdef CONFIG_MODULES #ifdef CONFIG_MODULES
static void free_module_param_attrs(struct module_kobject *mk) static void free_module_param_attrs(struct module_kobject *mk)
{ {
kfree(mk->mp->grp.attrs); if (mk->mp)
kfree(mk->mp->grp.attrs);
kfree(mk->mp); kfree(mk->mp);
mk->mp = NULL; mk->mp = NULL;
} }
@@ -695,8 +686,10 @@ int module_param_sysfs_setup(struct module *mod,
if (kparam[i].perm == 0) if (kparam[i].perm == 0)
continue; continue;
err = add_sysfs_param(&mod->mkobj, &kparam[i], kparam[i].name); err = add_sysfs_param(&mod->mkobj, &kparam[i], kparam[i].name);
if (err) if (err) {
free_module_param_attrs(&mod->mkobj);
return err; return err;
}
params = true; params = true;
} }