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security/selinux: fix /proc/sys/ labeling 

This fixes an old (2007) selinux regression: filesystem labeling for
/proc/sys returned
     -r--r--r-- unknown                          /proc/sys/fs/file-nr
instead of
     -r--r--r-- system_u:object_r:sysctl_fs_t:s0 /proc/sys/fs/file-nr

Events that lead to breaking of /proc/sys/ selinux labeling:

1) sysctl was reimplemented to route all calls through /proc/sys/

    commit 77b14db502
    [PATCH] sysctl: reimplement the sysctl proc support

2) proc_dir_entry was removed from ctl_table:

    commit 3fbfa98112
    [PATCH] sysctl: remove the proc_dir_entry member for the sysctl tables

3) selinux still walked the proc_dir_entry tree to apply
   labeling. Because ctl_tables don't have a proc_dir_entry, we did
   not label /proc/sys/ inodes any more. To achieve this the /proc/sys/
   inodes were marked private and private inodes were ignored by
   selinux.

    commit bbaca6c2e7
    [PATCH] selinux: enhance selinux to always ignore private inodes

    commit 86a71dbd3e
    [PATCH] sysctl: hide the sysctl proc inodes from selinux

Access control checks have been done by means of a special sysctl hook
that was called for read/write accesses to any /proc/sys/ entry.

We don't have to do this because, instead of walking the
proc_dir_entry tree we can walk the dentry tree (as done in this
patch). With this patch:
* we don't mark /proc/sys/ inodes as private
* we don't need the sysclt security hook
* we walk the dentry tree to find the path to the inode.

We have to strip the PID in /proc/PID/ entries that have a
proc_dir_entry because selinux does not know how to label paths like
'/1/net/rpc/nfsd.fh' (and defaults to 'proc_t' labeling). Selinux does
know of '/net/rpc/nfsd.fh' (and applies the 'sysctl_rpc_t' label).

PID stripping from the path was done implicitly in the previous code
because the proc_dir_entry tree had the root in '/net' in the example
from above. The dentry tree has the root in '/1'.

Signed-off-by: Eric W. Biederman <ebiederm@xmission.com>
Signed-off-by: Lucian Adrian Grijincu <lucian.grijincu@gmail.com>
Signed-off-by: Eric Paris <eparis@redhat.com>
This commit is contained in:
Lucian Adrian Grijincu 2011-02-01 18:42:22 +02:00 committed by Eric Paris
parent 652bb9b0d6
commit 8e6c96935f
2 changed files with 18 additions and 103 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

1
fs/proc/proc_sysctl.c
View File

@ -32,7 +32,6 @@ static struct inode *proc_sys_make_inode(struct super_block *sb,
ei->sysctl_entry = table;
inode->i_mtime = inode->i_atime = inode->i_ctime = CURRENT_TIME;
inode->i_flags |= S_PRIVATE; /* tell selinux to ignore this inode */
inode->i_mode = table->mode;
if (!table->child) {
inode->i_mode |= S_IFREG;

120
security/selinux/hooks.c
View File

@ -44,7 +44,6 @@
#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>
@ -71,7 +70,6 @@
#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>
@ -1121,39 +1119,35 @@ 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;
path = dentry_path_raw(dentry, buffer, PAGE_SIZE);
if (IS_ERR(path))
rc = PTR_ERR(path);
else {
/* each process gets a /proc/PID/ entry. Strip off the
* PID part to get a valid selinux labeling.
* e.g. /proc/1/net/rpc/nfs -> /net/rpc/nfs */
while (path[1] >= '0' && path[1] <= '9') {
path[1] = '/';
path++;
}
rc = security_genfs_sid("proc", path, tclass, sid);
}
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)
{
@ -1315,10 +1309,9 @@ 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)
@ -1861,82 +1854,6 @@ 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();
@ -5398,7 +5315,6 @@ 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,