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Date: Mon, 23 Nov 2009 09:18:32 +1100 (EST)
From: James Morris <jmorris@...ei.org>
To: "Eric W. Biederman" <ebiederm@...ssion.com>
cc: linux-kernel@...r.kernel.org,
linux-security-module@...r.kernel.org,
Stephen Smalley <sds@...ho.nsa.gov>,
Eric Paris <eparis@...hat.com>,
Tetsuo Handa <penguin-kernel@...ove.sakura.ne.jp>
Subject: Re: [RFC][PATCH] security/selinux: Simplify proc inode to security
label mapping.
On Fri, 20 Nov 2009, Eric W. Biederman wrote:
>
> Currently selinux has incestuous knowledge of the implementation details
> of procfs and sysctl that it uses to get a pathname from an inode. As it
> happens the point we care is in the security_d_instantiate lsm hook so
> we have a valid dentry that we can use to get the entire pathname on
> the proc filesystem. With the recent change to sys_sysctl to go through
> proc/sys all proc and sysctl accesses go through the vfs, which
> means we no longer need a sysctl special case.
I need to investigate this further, but one immediate issue is that
Tomoyo seems to have similar code.
> So get the path for the dentry, remove the incestuous knowledge
> and simplify the code.
>
> caveat: Because the dentry may not yet be hashed I think dentry_path will
> append (deleted) and thus is not the right function to call.
>
> Signed-off-by: Eric W. Biederman <ebiederm@...ssion.com>
> ---
> security/selinux/hooks.c | 114 ++++-----------------------------------------
> 1 files changed, 11 insertions(+), 103 deletions(-)
>
> diff --git a/security/selinux/hooks.c b/security/selinux/hooks.c
> index bb230d5..37ed36e 100644
> --- a/security/selinux/hooks.c
> +++ b/security/selinux/hooks.c
> @@ -43,7 +43,6 @@
> #include <linux/fdtable.h>
> #include <linux/namei.h>
> #include <linux/mount.h>
> -#include <linux/proc_fs.h>
> #include <linux/netfilter_ipv4.h>
> #include <linux/netfilter_ipv6.h>
> #include <linux/tty.h>
> @@ -70,7 +69,6 @@
> #include <net/ipv6.h>
> #include <linux/hugetlb.h>
> #include <linux/personality.h>
> -#include <linux/sysctl.h>
> #include <linux/audit.h>
> #include <linux/string.h>
> #include <linux/selinux.h>
> @@ -1178,39 +1176,27 @@ static inline u16 socket_type_to_security_class(int family, int type, int protoc
> }
>
> #ifdef CONFIG_PROC_FS
> -static int selinux_proc_get_sid(struct proc_dir_entry *de,
> +static int selinux_proc_get_sid(struct dentry *dentry,
> u16 tclass,
> u32 *sid)
> {
> - int buflen, rc;
> - char *buffer, *path, *end;
> + int rc;
> + char *buffer, *path;
>
> buffer = (char *)__get_free_page(GFP_KERNEL);
> if (!buffer)
> return -ENOMEM;
>
> - buflen = PAGE_SIZE;
> - end = buffer+buflen;
> - *--end = '\0';
> - buflen--;
> - path = end-1;
> - *path = '/';
> - while (de && de != de->parent) {
> - buflen -= de->namelen + 1;
> - if (buflen < 0)
> - break;
> - end -= de->namelen;
> - memcpy(end, de->name, de->namelen);
> - *--end = '/';
> - path = end;
> - de = de->parent;
> - }
> - rc = security_genfs_sid("proc", path, tclass, sid);
> + path = dentry_path(dentry, buffer, PAGE_SIZE);
> + if (IS_ERR(path))
> + rc = PTR_ERR(path);
> + else
> + rc = security_genfs_sid("proc", path, tclass, sid);
> free_page((unsigned long)buffer);
> return rc;
> }
> #else
> -static int selinux_proc_get_sid(struct proc_dir_entry *de,
> +static int selinux_proc_get_sid(struct dentry *dentry,
> u16 tclass,
> u32 *sid)
> {
> @@ -1374,10 +1360,9 @@ static int inode_doinit_with_dentry(struct inode *inode, struct dentry *opt_dent
> isec->sid = sbsec->sid;
>
> if ((sbsec->flags & SE_SBPROC) && !S_ISLNK(inode->i_mode)) {
> - struct proc_inode *proci = PROC_I(inode);
> - if (proci->pde) {
> + if (opt_dentry) {
> isec->sclass = inode_mode_to_security_class(inode->i_mode);
> - rc = selinux_proc_get_sid(proci->pde,
> + rc = selinux_proc_get_sid(opt_dentry,
> isec->sclass,
> &sid);
> if (rc)
> @@ -1939,82 +1924,6 @@ static int selinux_capable(struct task_struct *tsk, const struct cred *cred,
> return task_has_capability(tsk, cred, cap, audit);
> }
>
> -static int selinux_sysctl_get_sid(ctl_table *table, u16 tclass, u32 *sid)
> -{
> - int buflen, rc;
> - char *buffer, *path, *end;
> -
> - rc = -ENOMEM;
> - buffer = (char *)__get_free_page(GFP_KERNEL);
> - if (!buffer)
> - goto out;
> -
> - buflen = PAGE_SIZE;
> - end = buffer+buflen;
> - *--end = '\0';
> - buflen--;
> - path = end-1;
> - *path = '/';
> - while (table) {
> - const char *name = table->procname;
> - size_t namelen = strlen(name);
> - buflen -= namelen + 1;
> - if (buflen < 0)
> - goto out_free;
> - end -= namelen;
> - memcpy(end, name, namelen);
> - *--end = '/';
> - path = end;
> - table = table->parent;
> - }
> - buflen -= 4;
> - if (buflen < 0)
> - goto out_free;
> - end -= 4;
> - memcpy(end, "/sys", 4);
> - path = end;
> - rc = security_genfs_sid("proc", path, tclass, sid);
> -out_free:
> - free_page((unsigned long)buffer);
> -out:
> - return rc;
> -}
> -
> -static int selinux_sysctl(ctl_table *table, int op)
> -{
> - int error = 0;
> - u32 av;
> - u32 tsid, sid;
> - int rc;
> -
> - sid = current_sid();
> -
> - rc = selinux_sysctl_get_sid(table, (op == 0001) ?
> - SECCLASS_DIR : SECCLASS_FILE, &tsid);
> - if (rc) {
> - /* Default to the well-defined sysctl SID. */
> - tsid = SECINITSID_SYSCTL;
> - }
> -
> - /* The op values are "defined" in sysctl.c, thereby creating
> - * a bad coupling between this module and sysctl.c */
> - if (op == 001) {
> - error = avc_has_perm(sid, tsid,
> - SECCLASS_DIR, DIR__SEARCH, NULL);
> - } else {
> - av = 0;
> - if (op & 004)
> - av |= FILE__READ;
> - if (op & 002)
> - av |= FILE__WRITE;
> - if (av)
> - error = avc_has_perm(sid, tsid,
> - SECCLASS_FILE, av, NULL);
> - }
> -
> - return error;
> -}
> -
> static int selinux_quotactl(int cmds, int type, int id, struct super_block *sb)
> {
> const struct cred *cred = current_cred();
> @@ -5457,7 +5366,6 @@ static struct security_operations selinux_ops = {
> .ptrace_traceme = selinux_ptrace_traceme,
> .capget = selinux_capget,
> .capset = selinux_capset,
> - .sysctl = selinux_sysctl,
> .capable = selinux_capable,
> .quotactl = selinux_quotactl,
> .quota_on = selinux_quota_on,
> --
> 1.6.5.2.143.g8cc62
>
--
James Morris
<jmorris@...ei.org>
--
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