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selinux: parse contexts for mount options early
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Commit b8b87fd ("selinux: Fix selinux_sb_mnt_opts_compat()")
started to parse mount options into SIDs in selinux_add_opt() if policy
has already been loaded. Since it's extremely unlikely that anyone would
depend on the ability to set SELinux contexts on fs_context before
loading the policy and then mounting that context after simplify the
logic by always parsing the options early.

Note that the multi-step mounting is only possible with the new
fscontext mount API and wasn't possible before its introduction.

Signed-off-by: Ondrej Mosnacek <omosnace@redhat.com>
Signed-off-by: Paul Moore <paul@paul-moore.com>
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@WOnder93 @pcmoore
WOnder93 authored and pcmoore committed Feb 4, 2022
1 parent 0e326df commit 70f4169
Showing 1 changed file with 53 additions and 149 deletions.
202 changes: 53 additions & 149 deletions security/selinux/hooks.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -340,7 +340,6 @@ static void inode_free_security(struct inode *inode)
}

struct selinux_mnt_opts {
const char *fscontext, *context, *rootcontext, *defcontext;
u32 fscontext_sid;
u32 context_sid;
u32 rootcontext_sid;
Expand All @@ -349,12 +348,7 @@ struct selinux_mnt_opts {

static void selinux_free_mnt_opts(void *mnt_opts)
{
struct selinux_mnt_opts *opts = mnt_opts;
kfree(opts->fscontext);
kfree(opts->context);
kfree(opts->rootcontext);
kfree(opts->defcontext);
kfree(opts);
kfree(mnt_opts);
}

enum {
Expand Down Expand Up @@ -601,17 +595,6 @@ static int bad_option(struct superblock_security_struct *sbsec, char flag,
return 0;
}

static int parse_sid(struct super_block *sb, const char *s, u32 *sid)
{
int rc = security_context_str_to_sid(&selinux_state, s,
sid, GFP_KERNEL);
if (rc)
pr_warn("SELinux: security_context_str_to_sid"
"(%s) failed for (dev %s, type %s) errno=%d\n",
s, sb ? sb->s_id : "?", sb ? sb->s_type->name : "?", rc);
return rc;
}

/*
* Allow filesystems with binary mount data to explicitly set mount point
* labeling information.
Expand Down Expand Up @@ -674,49 +657,29 @@ static int selinux_set_mnt_opts(struct super_block *sb,
* than once with different security options.
*/
if (opts) {
if (opts->fscontext) {
if (opts->fscontext_sid == SECSID_NULL) {
rc = parse_sid(sb, opts->fscontext, &fscontext_sid);
if (rc)
goto out;
} else
fscontext_sid = opts->fscontext_sid;
if (opts->fscontext_sid) {
fscontext_sid = opts->fscontext_sid;
if (bad_option(sbsec, FSCONTEXT_MNT, sbsec->sid,
fscontext_sid))
goto out_double_mount;
sbsec->flags |= FSCONTEXT_MNT;
}
if (opts->context) {
if (opts->context_sid == SECSID_NULL) {
rc = parse_sid(sb, opts->context, &context_sid);
if (rc)
goto out;
} else
context_sid = opts->context_sid;
if (opts->context_sid) {
context_sid = opts->context_sid;
if (bad_option(sbsec, CONTEXT_MNT, sbsec->mntpoint_sid,
context_sid))
goto out_double_mount;
sbsec->flags |= CONTEXT_MNT;
}
if (opts->rootcontext) {
if (opts->rootcontext_sid == SECSID_NULL) {
rc = parse_sid(sb, opts->rootcontext, &rootcontext_sid);
if (rc)
goto out;
} else
rootcontext_sid = opts->rootcontext_sid;
if (opts->rootcontext_sid) {
rootcontext_sid = opts->rootcontext_sid;
if (bad_option(sbsec, ROOTCONTEXT_MNT, root_isec->sid,
rootcontext_sid))
goto out_double_mount;
sbsec->flags |= ROOTCONTEXT_MNT;
}
if (opts->defcontext) {
if (opts->defcontext_sid == SECSID_NULL) {
rc = parse_sid(sb, opts->defcontext, &defcontext_sid);
if (rc)
goto out;
} else
defcontext_sid = opts->defcontext_sid;
if (opts->defcontext_sid) {
defcontext_sid = opts->defcontext_sid;
if (bad_option(sbsec, DEFCONTEXT_MNT, sbsec->def_sid,
defcontext_sid))
goto out_double_mount;
Expand Down Expand Up @@ -986,13 +949,20 @@ static int selinux_add_opt(int token, const char *s, void **mnt_opts)
{
struct selinux_mnt_opts *opts = *mnt_opts;
bool is_alloc_opts = false;
u32 *dst_sid;
int rc;

if (token == Opt_seclabel)
/* eaten and completely ignored */
return 0;
if (!s)
return -ENOMEM;

if (!selinux_initialized(&selinux_state)) {
pr_warn("SELinux: Unable to set superblock options before the security server is initialized\n");
return -EINVAL;
}

if (!opts) {
opts = kzalloc(sizeof(*opts), GFP_KERNEL);
if (!opts)
Expand All @@ -1003,36 +973,34 @@ static int selinux_add_opt(int token, const char *s, void **mnt_opts)

switch (token) {
case Opt_context:
if (opts->context || opts->defcontext)
if (opts->context_sid || opts->defcontext_sid)
goto err;
opts->context = s;
if (selinux_initialized(&selinux_state))
parse_sid(NULL, s, &opts->context_sid);
dst_sid = &opts->context_sid;
break;
case Opt_fscontext:
if (opts->fscontext)
if (opts->fscontext_sid)
goto err;
opts->fscontext = s;
if (selinux_initialized(&selinux_state))
parse_sid(NULL, s, &opts->fscontext_sid);
dst_sid = &opts->fscontext_sid;
break;
case Opt_rootcontext:
if (opts->rootcontext)
if (opts->rootcontext_sid)
goto err;
opts->rootcontext = s;
if (selinux_initialized(&selinux_state))
parse_sid(NULL, s, &opts->rootcontext_sid);
dst_sid = &opts->rootcontext_sid;
break;
case Opt_defcontext:
if (opts->context || opts->defcontext)
if (opts->context_sid || opts->defcontext_sid)
goto err;
opts->defcontext = s;
if (selinux_initialized(&selinux_state))
parse_sid(NULL, s, &opts->defcontext_sid);
dst_sid = &opts->defcontext_sid;
break;
default:
WARN_ON(1);
return -EINVAL;
}

return 0;
rc = security_context_str_to_sid(&selinux_state, s, dst_sid, GFP_KERNEL);
if (rc)
pr_warn("SELinux: security_context_str_to_sid (%s) failed with errno=%d\n",
s, rc);
return rc;

err:
if (is_alloc_opts) {
Expand Down Expand Up @@ -2681,37 +2649,27 @@ static int selinux_sb_mnt_opts_compat(struct super_block *sb, void *mnt_opts)
if (!opts)
return (sbsec->flags & SE_MNTMASK) ? 1 : 0;

if (opts->fscontext) {
if (opts->fscontext_sid == SECSID_NULL)
return 1;
else if (bad_option(sbsec, FSCONTEXT_MNT, sbsec->sid,
opts->fscontext_sid))
if (opts->fscontext_sid) {
if (bad_option(sbsec, FSCONTEXT_MNT, sbsec->sid,
opts->fscontext_sid))
return 1;
}
if (opts->context) {
if (opts->context_sid == SECSID_NULL)
return 1;
else if (bad_option(sbsec, CONTEXT_MNT, sbsec->mntpoint_sid,
opts->context_sid))
if (opts->context_sid) {
if (bad_option(sbsec, CONTEXT_MNT, sbsec->mntpoint_sid,
opts->context_sid))
return 1;
}
if (opts->rootcontext) {
if (opts->rootcontext_sid == SECSID_NULL)
return 1;
else {
struct inode_security_struct *root_isec;
if (opts->rootcontext_sid) {
struct inode_security_struct *root_isec;

root_isec = backing_inode_security(sb->s_root);
if (bad_option(sbsec, ROOTCONTEXT_MNT, root_isec->sid,
opts->rootcontext_sid))
return 1;
}
}
if (opts->defcontext) {
if (opts->defcontext_sid == SECSID_NULL)
root_isec = backing_inode_security(sb->s_root);
if (bad_option(sbsec, ROOTCONTEXT_MNT, root_isec->sid,
opts->rootcontext_sid))
return 1;
else if (bad_option(sbsec, DEFCONTEXT_MNT, sbsec->def_sid,
opts->defcontext_sid))
}
if (opts->defcontext_sid) {
if (bad_option(sbsec, DEFCONTEXT_MNT, sbsec->def_sid,
opts->defcontext_sid))
return 1;
}
return 0;
Expand All @@ -2721,55 +2679,31 @@ static int selinux_sb_remount(struct super_block *sb, void *mnt_opts)
{
struct selinux_mnt_opts *opts = mnt_opts;
struct superblock_security_struct *sbsec = selinux_superblock(sb);
int rc;

if (!(sbsec->flags & SE_SBINITIALIZED))
return 0;

if (!opts)
return 0;

if (opts->fscontext) {
if (opts->fscontext_sid == SECSID_NULL) {
rc = parse_sid(sb, opts->fscontext,
&opts->fscontext_sid);
if (rc)
return rc;
}
if (opts->fscontext_sid) {
if (bad_option(sbsec, FSCONTEXT_MNT, sbsec->sid,
opts->fscontext_sid))
goto out_bad_option;
}
if (opts->context) {
if (opts->context_sid == SECSID_NULL) {
rc = parse_sid(sb, opts->context, &opts->context_sid);
if (rc)
return rc;
}
if (opts->context_sid) {
if (bad_option(sbsec, CONTEXT_MNT, sbsec->mntpoint_sid,
opts->context_sid))
goto out_bad_option;
}
if (opts->rootcontext) {
if (opts->rootcontext_sid) {
struct inode_security_struct *root_isec;
root_isec = backing_inode_security(sb->s_root);
if (opts->rootcontext_sid == SECSID_NULL) {
rc = parse_sid(sb, opts->rootcontext,
&opts->rootcontext_sid);
if (rc)
return rc;
}
if (bad_option(sbsec, ROOTCONTEXT_MNT, root_isec->sid,
opts->rootcontext_sid))
goto out_bad_option;
}
if (opts->defcontext) {
if (opts->defcontext_sid == SECSID_NULL) {
rc = parse_sid(sb, opts->defcontext,
&opts->defcontext_sid);
if (rc)
return rc;
}
if (opts->defcontext_sid) {
if (bad_option(sbsec, DEFCONTEXT_MNT, sbsec->def_sid,
opts->defcontext_sid))
goto out_bad_option;
Expand Down Expand Up @@ -2838,42 +2772,12 @@ static int selinux_fs_context_dup(struct fs_context *fc,
struct fs_context *src_fc)
{
const struct selinux_mnt_opts *src = src_fc->security;
struct selinux_mnt_opts *opts;

if (!src)
return 0;

fc->security = kzalloc(sizeof(struct selinux_mnt_opts), GFP_KERNEL);
if (!fc->security)
return -ENOMEM;

opts = fc->security;

if (src->fscontext) {
opts->fscontext = kstrdup(src->fscontext, GFP_KERNEL);
if (!opts->fscontext)
return -ENOMEM;
}
if (src->context) {
opts->context = kstrdup(src->context, GFP_KERNEL);
if (!opts->context)
return -ENOMEM;
}
if (src->rootcontext) {
opts->rootcontext = kstrdup(src->rootcontext, GFP_KERNEL);
if (!opts->rootcontext)
return -ENOMEM;
}
if (src->defcontext) {
opts->defcontext = kstrdup(src->defcontext, GFP_KERNEL);
if (!opts->defcontext)
return -ENOMEM;
}
opts->fscontext_sid = src->fscontext_sid;
opts->context_sid = src->context_sid;
opts->rootcontext_sid = src->rootcontext_sid;
opts->defcontext_sid = src->defcontext_sid;
return 0;
fc->security = kmemdup(src, sizeof(*src), GFP_KERNEL);
return fc->security ? 0 : -ENOMEM;
}

static const struct fs_parameter_spec selinux_fs_parameters[] = {
Expand Down

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