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SELinux: implement the new sb_remount LSM hook 

For SELinux we do not allow security information to change during a remount
operation.  Thus this hook simply strips the security module options from
the data and verifies that those are the same options as exist on the
current superblock.

Signed-off-by: Eric Paris <eparis@redhat.com>
Reviewed-by: James Morris <jmorris@namei.org>
hifive-unleashed-5.1
Eric Paris 2011-03-03 16:09:14 -05:00
parent ff36fe2c84
commit 026eb167ae
1 changed files with 86 additions and 0 deletions
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86
security/selinux/hooks.c
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@ -2363,6 +2363,91 @@ out:
return rc;
}
static int selinux_sb_remount(struct super_block *sb, void *data)
{
int rc, i, *flags;
struct security_mnt_opts opts;
char *secdata, **mount_options;
struct superblock_security_struct *sbsec = sb->s_security;
if (!(sbsec->flags & SE_SBINITIALIZED))
return 0;
if (!data)
return 0;
if (sb->s_type->fs_flags & FS_BINARY_MOUNTDATA)
return 0;
security_init_mnt_opts(&opts);
secdata = alloc_secdata();
if (!secdata)
return -ENOMEM;
rc = selinux_sb_copy_data(data, secdata);
if (rc)
goto out_free_secdata;
rc = selinux_parse_opts_str(secdata, &opts);
if (rc)
goto out_free_secdata;
mount_options = opts.mnt_opts;
flags = opts.mnt_opts_flags;
for (i = 0; i < opts.num_mnt_opts; i++) {
u32 sid;
size_t len;
if (flags[i] == SE_SBLABELSUPP)
continue;
len = strlen(mount_options[i]);
rc = security_context_to_sid(mount_options[i], len, &sid);
if (rc) {
printk(KERN_WARNING "SELinux: security_context_to_sid"
"(%s) failed for (dev %s, type %s) errno=%d\n",
mount_options[i], sb->s_id, sb->s_type->name, rc);
goto out_free_opts;
}
rc = -EINVAL;
switch (flags[i]) {
case FSCONTEXT_MNT:
if (bad_option(sbsec, FSCONTEXT_MNT, sbsec->sid, sid))
goto out_bad_option;
break;
case CONTEXT_MNT:
if (bad_option(sbsec, CONTEXT_MNT, sbsec->mntpoint_sid, sid))
goto out_bad_option;
break;
case ROOTCONTEXT_MNT: {
struct inode_security_struct *root_isec;
root_isec = sb->s_root->d_inode->i_security;
if (bad_option(sbsec, ROOTCONTEXT_MNT, root_isec->sid, sid))
goto out_bad_option;
break;
}
case DEFCONTEXT_MNT:
if (bad_option(sbsec, DEFCONTEXT_MNT, sbsec->def_sid, sid))
goto out_bad_option;
break;
default:
goto out_free_opts;
}
}
rc = 0;
out_free_opts:
security_free_mnt_opts(&opts);
out_free_secdata:
free_secdata(secdata);
return rc;
out_bad_option:
printk(KERN_WARNING "SELinux: unable to change security options "
"during remount (dev %s, type=%s)\n", sb->s_id,
sb->s_type->name);
goto out_free_opts;
}
static int selinux_sb_kern_mount(struct super_block *sb, int flags, void *data)
{
const struct cred *cred = current_cred();
@ -5356,6 +5441,7 @@ static struct security_operations selinux_ops = {
.sb_alloc_security = selinux_sb_alloc_security,
.sb_free_security = selinux_sb_free_security,
.sb_copy_data = selinux_sb_copy_data,
.sb_remount = selinux_sb_remount,
.sb_kern_mount = selinux_sb_kern_mount,
.sb_show_options = selinux_sb_show_options,
.sb_statfs = selinux_sb_statfs,