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Subject[PATCH 1/2] security/selinux: fix /proc/sys/ labeling
Date
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 77b14db502cb85a031fe8fde6c85d52f3e0acb63
[PATCH] sysctl: reimplement the sysctl proc support

2) proc_dir_entry was removed from ctl_table:

commit 3fbfa98112fc3962c416452a0baf2214381030e6
[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 bbaca6c2e7ef0f663bc31be4dad7cf530f6c4962
[PATCH] selinux: enhance selinux to always ignore private inodes

commit 86a71dbd3e81e8870d0f0e56b87875f57e58222b
[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>
---
fs/proc/proc_sysctl.c | 1 -
security/selinux/hooks.c | 120 +++++++---------------------------------------
2 files changed, 18 insertions(+), 103 deletions(-)

diff --git a/fs/proc/proc_sysctl.c b/fs/proc/proc_sysctl.c
index 09a1f92..fb707e0 100644
--- a/fs/proc/proc_sysctl.c
+++ b/fs/proc/proc_sysctl.c
@@ -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;
diff --git a/security/selinux/hooks.c b/security/selinux/hooks.c
index e276eb4..5231b95 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>
@@ -1120,39 +1118,35 @@ 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)
{
@@ -1316,10 +1310,9 @@ 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)
@@ -1862,82 +1855,6 @@ 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,
--
1.7.4.rc1.7.g2cf08.dirty


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