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Message-ID: <20080624162122.GC4993@us.ibm.com>
Date: Tue, 24 Jun 2008 11:21:23 -0500
From: "Serge E. Hallyn" <serue@...ibm.com>
To: menage@...gle.com
Cc: pj@....com, xemul@...nvz.org, balbir@...ibm.com, serue@...ibm.com,
akpm@...ux-foundation.org, linux-kernel@...r.kernel.org,
containers@...ts.linux-foundation.org
Subject: Re: [PATCH 7/8] CGroup Files: Convert devcgroup_access_write()
into a cgroup write_string() handler
Quoting menage@...gle.com (menage@...gle.com):
> This patch converts devcgroup_access_write() from a raw file handler
> into a handler for the cgroup write_string() method. This allows some
> boilerplate copying/locking/checking to be removed and simplifies the
> cleanup path, since these functions are performed by the cgroups
> framework before calling the handler.
>
> Signed-off-by: Paul Menage <menage@...gle.com>
Looks good. I'll have to test later.
Acked-by: Serge Hallyn <serue@...ibm.com>
thanks,
-serge
>
> ---
> security/device_cgroup.c | 103 +++++++++++++++++------------------------------
> 1 file changed, 39 insertions(+), 64 deletions(-)
>
> Index: cws-2.6.26-rc5-mm3/security/device_cgroup.c
> ===================================================================
> --- cws-2.6.26-rc5-mm3.orig/security/device_cgroup.c
> +++ cws-2.6.26-rc5-mm3/security/device_cgroup.c
> @@ -59,6 +59,11 @@ static inline struct dev_cgroup *cgroup_
> return css_to_devcgroup(cgroup_subsys_state(cgroup, devices_subsys_id));
> }
>
> +static inline struct dev_cgroup *task_devcgroup(struct task_struct *task)
> +{
> + return css_to_devcgroup(task_subsys_state(task, devices_subsys_id));
> +}
> +
> struct cgroup_subsys devices_subsys;
>
> static int devcgroup_can_attach(struct cgroup_subsys *ss,
> @@ -312,10 +317,10 @@ static int may_access_whitelist(struct d
> * when adding a new allow rule to a device whitelist, the rule
> * must be allowed in the parent device
> */
> -static int parent_has_perm(struct cgroup *childcg,
> +static int parent_has_perm(struct dev_cgroup *childcg,
> struct dev_whitelist_item *wh)
> {
> - struct cgroup *pcg = childcg->parent;
> + struct cgroup *pcg = childcg->css.cgroup->parent;
> struct dev_cgroup *parent;
> int ret;
>
> @@ -341,39 +346,18 @@ static int parent_has_perm(struct cgroup
> * new access is only allowed if you're in the top-level cgroup, or your
> * parent cgroup has the access you're asking for.
> */
> -static ssize_t devcgroup_access_write(struct cgroup *cgroup, struct cftype *cft,
> - struct file *file, const char __user *userbuf,
> - size_t nbytes, loff_t *ppos)
> -{
> - struct cgroup *cur_cgroup;
> - struct dev_cgroup *devcgroup, *cur_devcgroup;
> - int filetype = cft->private;
> - char *buffer, *b;
> +static int devcgroup_update_access(struct dev_cgroup *devcgroup,
> + int filetype, const char *buffer)
> +{
> + struct dev_cgroup *cur_devcgroup;
> + const char *b;
> int retval = 0, count;
> struct dev_whitelist_item wh;
>
> if (!capable(CAP_SYS_ADMIN))
> return -EPERM;
>
> - devcgroup = cgroup_to_devcgroup(cgroup);
> - cur_cgroup = task_cgroup(current, devices_subsys.subsys_id);
> - cur_devcgroup = cgroup_to_devcgroup(cur_cgroup);
> -
> - buffer = kmalloc(nbytes+1, GFP_KERNEL);
> - if (!buffer)
> - return -ENOMEM;
> -
> - if (copy_from_user(buffer, userbuf, nbytes)) {
> - retval = -EFAULT;
> - goto out1;
> - }
> - buffer[nbytes] = 0; /* nul-terminate */
> -
> - cgroup_lock();
> - if (cgroup_is_removed(cgroup)) {
> - retval = -ENODEV;
> - goto out2;
> - }
> + cur_devcgroup = task_devcgroup(current);
>
> memset(&wh, 0, sizeof(wh));
> b = buffer;
> @@ -390,14 +374,11 @@ static ssize_t devcgroup_access_write(st
> wh.type = DEV_CHAR;
> break;
> default:
> - retval = -EINVAL;
> - goto out2;
> + return -EINVAL;
> }
> b++;
> - if (!isspace(*b)) {
> - retval = -EINVAL;
> - goto out2;
> - }
> + if (!isspace(*b))
> + return -EINVAL;
> b++;
> if (*b == '*') {
> wh.major = ~0;
> @@ -409,13 +390,10 @@ static ssize_t devcgroup_access_write(st
> b++;
> }
> } else {
> - retval = -EINVAL;
> - goto out2;
> - }
> - if (*b != ':') {
> - retval = -EINVAL;
> - goto out2;
> + return -EINVAL;
> }
> + if (*b != ':')
> + return -EINVAL;
> b++;
>
> /* read minor */
> @@ -429,13 +407,10 @@ static ssize_t devcgroup_access_write(st
> b++;
> }
> } else {
> - retval = -EINVAL;
> - goto out2;
> - }
> - if (!isspace(*b)) {
> - retval = -EINVAL;
> - goto out2;
> + return -EINVAL;
> }
> + if (!isspace(*b))
> + return -EINVAL;
> for (b++, count = 0; count < 3; count++, b++) {
> switch (*b) {
> case 'r':
> @@ -452,8 +427,7 @@ static ssize_t devcgroup_access_write(st
> count = 3;
> break;
> default:
> - retval = -EINVAL;
> - goto out2;
> + return -EINVAL;
> }
> }
>
> @@ -461,38 +435,39 @@ handle:
> retval = 0;
> switch (filetype) {
> case DEVCG_ALLOW:
> - if (!parent_has_perm(cgroup, &wh))
> - retval = -EPERM;
> - else
> - retval = dev_whitelist_add(devcgroup, &wh);
> - break;
> + if (!parent_has_perm(devcgroup, &wh))
> + return -EPERM;
> + return dev_whitelist_add(devcgroup, &wh);
> case DEVCG_DENY:
> dev_whitelist_rm(devcgroup, &wh);
> break;
> default:
> - retval = -EINVAL;
> - goto out2;
> + return -EINVAL;
> }
> + return 0;
> +}
>
> - if (retval == 0)
> - retval = nbytes;
> -
> -out2:
> +static int devcgroup_access_write(struct cgroup *cgrp, struct cftype *cft,
> + const char *buffer)
> +{
> + int retval;
> + if (!cgroup_lock_live_group(cgrp))
> + return -ENODEV;
> + retval = devcgroup_update_access(cgroup_to_devcgroup(cgrp),
> + cft->private, buffer);
> cgroup_unlock();
> -out1:
> - kfree(buffer);
> return retval;
> }
>
> static struct cftype dev_cgroup_files[] = {
> {
> .name = "allow",
> - .write = devcgroup_access_write,
> + .write_string = devcgroup_access_write,
> .private = DEVCG_ALLOW,
> },
> {
> .name = "deny",
> - .write = devcgroup_access_write,
> + .write_string = devcgroup_access_write,
> .private = DEVCG_DENY,
> },
> {
>
> --
--
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