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Merge tag 'selinux-pr-20190305' of git://git.kernel.org/pub/scm/linux…
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…/kernel/git/pcmoore/selinux

Pull SELinux updates from Paul Moore:
 "Nine SELinux patches for v5.1, all bug fixes.

  As far as I'm concerned, nothing really jumps out as risky or special
  to me, but each commit has a decent description so you can judge for
  yourself. As usual, everything passes the selinux-testsuite; please
  merge for v5.1"

* tag 'selinux-pr-20190305' of git://git.kernel.org/pub/scm/linux/kernel/git/pcmoore/selinux:
  selinux: fix avc audit messages
  selinux: replace BUG_ONs with WARN_ONs in avc.c
  selinux: log invalid contexts in AVCs
  selinux: replace some BUG_ON()s with a WARN_ON()
  selinux: inline some AVC functions used only once
  selinux: do not override context on context mounts
  selinux: never allow relabeling on context mounts
  selinux: stop passing MAY_NOT_BLOCK to the AVC upon follow_link
  selinux: avoid silent denials in permissive mode under RCU walk
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@torvalds
torvalds committed Mar 7, 2019
2 parents ae5906c + 45189a1 commit 3ac96c3
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Showing 5 changed files with 176 additions and 127 deletions.
199 changes: 96 additions & 103 deletions security/selinux/avc.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -129,75 +129,6 @@ static inline int avc_hash(u32 ssid, u32 tsid, u16 tclass)
return (ssid ^ (tsid<<2) ^ (tclass<<4)) & (AVC_CACHE_SLOTS - 1);
}

/**
* avc_dump_av - Display an access vector in human-readable form.
* @tclass: target security class
* @av: access vector
*/
static void avc_dump_av(struct audit_buffer *ab, u16 tclass, u32 av)
{
const char **perms;
int i, perm;

if (av == 0) {
audit_log_format(ab, " null");
return;
}

BUG_ON(!tclass || tclass >= ARRAY_SIZE(secclass_map));
perms = secclass_map[tclass-1].perms;

audit_log_format(ab, " {");
i = 0;
perm = 1;
while (i < (sizeof(av) * 8)) {
if ((perm & av) && perms[i]) {
audit_log_format(ab, " %s", perms[i]);
av &= ~perm;
}
i++;
perm <<= 1;
}

if (av)
audit_log_format(ab, " 0x%x", av);

audit_log_format(ab, " }");
}

/**
* avc_dump_query - Display a SID pair and a class in human-readable form.
* @ssid: source security identifier
* @tsid: target security identifier
* @tclass: target security class
*/
static void avc_dump_query(struct audit_buffer *ab, struct selinux_state *state,
u32 ssid, u32 tsid, u16 tclass)
{
int rc;
char *scontext;
u32 scontext_len;

rc = security_sid_to_context(state, ssid, &scontext, &scontext_len);
if (rc)
audit_log_format(ab, "ssid=%d", ssid);
else {
audit_log_format(ab, "scontext=%s", scontext);
kfree(scontext);
}

rc = security_sid_to_context(state, tsid, &scontext, &scontext_len);
if (rc)
audit_log_format(ab, " tsid=%d", tsid);
else {
audit_log_format(ab, " tcontext=%s", scontext);
kfree(scontext);
}

BUG_ON(!tclass || tclass >= ARRAY_SIZE(secclass_map));
audit_log_format(ab, " tclass=%s", secclass_map[tclass-1].name);
}

/**
* avc_init - Initialize the AVC.
*
Expand Down Expand Up @@ -735,11 +666,36 @@ static struct avc_node *avc_insert(struct selinux_avc *avc,
static void avc_audit_pre_callback(struct audit_buffer *ab, void *a)
{
struct common_audit_data *ad = a;
audit_log_format(ab, "avc: %s ",
ad->selinux_audit_data->denied ? "denied" : "granted");
avc_dump_av(ab, ad->selinux_audit_data->tclass,
ad->selinux_audit_data->audited);
audit_log_format(ab, " for ");
struct selinux_audit_data *sad = ad->selinux_audit_data;
u32 av = sad->audited;
const char **perms;
int i, perm;

audit_log_format(ab, "avc: %s ", sad->denied ? "denied" : "granted");

if (av == 0) {
audit_log_format(ab, " null");
return;
}

perms = secclass_map[sad->tclass-1].perms;

audit_log_format(ab, " {");
i = 0;
perm = 1;
while (i < (sizeof(av) * 8)) {
if ((perm & av) && perms[i]) {
audit_log_format(ab, " %s", perms[i]);
av &= ~perm;
}
i++;
perm <<= 1;
}

if (av)
audit_log_format(ab, " 0x%x", av);

audit_log_format(ab, " } for ");
}

/**
Expand All @@ -751,14 +707,47 @@ static void avc_audit_pre_callback(struct audit_buffer *ab, void *a)
static void avc_audit_post_callback(struct audit_buffer *ab, void *a)
{
struct common_audit_data *ad = a;
audit_log_format(ab, " ");
avc_dump_query(ab, ad->selinux_audit_data->state,
ad->selinux_audit_data->ssid,
ad->selinux_audit_data->tsid,
ad->selinux_audit_data->tclass);
if (ad->selinux_audit_data->denied) {
audit_log_format(ab, " permissive=%u",
ad->selinux_audit_data->result ? 0 : 1);
struct selinux_audit_data *sad = ad->selinux_audit_data;
char *scontext;
u32 scontext_len;
int rc;

rc = security_sid_to_context(sad->state, sad->ssid, &scontext,
&scontext_len);
if (rc)
audit_log_format(ab, " ssid=%d", sad->ssid);
else {
audit_log_format(ab, " scontext=%s", scontext);
kfree(scontext);
}

rc = security_sid_to_context(sad->state, sad->tsid, &scontext,
&scontext_len);
if (rc)
audit_log_format(ab, " tsid=%d", sad->tsid);
else {
audit_log_format(ab, " tcontext=%s", scontext);
kfree(scontext);
}

audit_log_format(ab, " tclass=%s", secclass_map[sad->tclass-1].name);

if (sad->denied)
audit_log_format(ab, " permissive=%u", sad->result ? 0 : 1);

/* in case of invalid context report also the actual context string */
rc = security_sid_to_context_inval(sad->state, sad->ssid, &scontext,
&scontext_len);
if (!rc && scontext) {
audit_log_format(ab, " srawcon=%s", scontext);
kfree(scontext);
}

rc = security_sid_to_context_inval(sad->state, sad->tsid, &scontext,
&scontext_len);
if (!rc && scontext) {
audit_log_format(ab, " trawcon=%s", scontext);
kfree(scontext);
}
}

Expand All @@ -772,6 +761,9 @@ noinline int slow_avc_audit(struct selinux_state *state,
struct common_audit_data stack_data;
struct selinux_audit_data sad;

if (WARN_ON(!tclass || tclass >= ARRAY_SIZE(secclass_map)))
return -EINVAL;

if (!a) {
a = &stack_data;
a->type = LSM_AUDIT_DATA_NONE;
Expand Down Expand Up @@ -838,6 +830,7 @@ int __init avc_add_callback(int (*callback)(u32 event), u32 events)
* @ssid,@tsid,@tclass : identifier of an AVC entry
* @seqno : sequence number when decision was made
* @xpd: extended_perms_decision to be added to the node
* @flags: the AVC_* flags, e.g. AVC_NONBLOCKING, AVC_EXTENDED_PERMS, or 0.
*
* if a valid AVC entry doesn't exist,this function returns -ENOENT.
* if kmalloc() called internal returns NULL, this function returns -ENOMEM.
Expand All @@ -856,6 +849,22 @@ static int avc_update_node(struct selinux_avc *avc,
struct hlist_head *head;
spinlock_t *lock;

/*
* If we are in a non-blocking code path, e.g. VFS RCU walk,
* then we must not add permissions to a cache entry
* because we cannot safely audit the denial. Otherwise,
* during the subsequent blocking retry (e.g. VFS ref walk), we
* will find the permissions already granted in the cache entry
* and won't audit anything at all, leading to silent denials in
* permissive mode that only appear when in enforcing mode.
*
* See the corresponding handling in slow_avc_audit(), and the
* logic in selinux_inode_permission for the MAY_NOT_BLOCK flag,
* which is transliterated into AVC_NONBLOCKING.
*/
if (flags & AVC_NONBLOCKING)
return 0;

node = avc_alloc_node(avc);
if (!node) {
rc = -ENOMEM;
Expand Down Expand Up @@ -1050,7 +1059,8 @@ int avc_has_extended_perms(struct selinux_state *state,
int rc = 0, rc2;

xp_node = &local_xp_node;
BUG_ON(!requested);
if (WARN_ON(!requested))
return -EACCES;

rcu_read_lock();

Expand Down Expand Up @@ -1115,7 +1125,7 @@ int avc_has_extended_perms(struct selinux_state *state,
* @tsid: target security identifier
* @tclass: target security class
* @requested: requested permissions, interpreted based on @tclass
* @flags: AVC_STRICT or 0
* @flags: AVC_STRICT, AVC_NONBLOCKING, or 0
* @avd: access vector decisions
*
* Check the AVC to determine whether the @requested permissions are granted
Expand All @@ -1140,7 +1150,8 @@ inline int avc_has_perm_noaudit(struct selinux_state *state,
int rc = 0;
u32 denied;

BUG_ON(!requested);
if (WARN_ON(!requested))
return -EACCES;

rcu_read_lock();

Expand Down Expand Up @@ -1191,24 +1202,6 @@ int avc_has_perm(struct selinux_state *state, u32 ssid, u32 tsid, u16 tclass,
return rc;
}

int avc_has_perm_flags(struct selinux_state *state,
u32 ssid, u32 tsid, u16 tclass, u32 requested,
struct common_audit_data *auditdata,
int flags)
{
struct av_decision avd;
int rc, rc2;

rc = avc_has_perm_noaudit(state, ssid, tsid, tclass, requested, 0,
&avd);

rc2 = avc_audit(state, ssid, tsid, tclass, requested, &avd, rc,
auditdata, flags);
if (rc2)
return rc2;
return rc;
}

u32 avc_policy_seqno(struct selinux_state *state)
{
return state->avc->avc_cache.latest_notif;
Expand Down
58 changes: 44 additions & 14 deletions security/selinux/hooks.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -490,16 +490,10 @@ static int may_context_mount_inode_relabel(u32 sid,
return rc;
}

static int selinux_is_sblabel_mnt(struct super_block *sb)
static int selinux_is_genfs_special_handling(struct super_block *sb)
{
struct superblock_security_struct *sbsec = sb->s_security;

return sbsec->behavior == SECURITY_FS_USE_XATTR ||
sbsec->behavior == SECURITY_FS_USE_TRANS ||
sbsec->behavior == SECURITY_FS_USE_TASK ||
sbsec->behavior == SECURITY_FS_USE_NATIVE ||
/* Special handling. Genfs but also in-core setxattr handler */
!strcmp(sb->s_type->name, "sysfs") ||
/* Special handling. Genfs but also in-core setxattr handler */
return !strcmp(sb->s_type->name, "sysfs") ||
!strcmp(sb->s_type->name, "pstore") ||
!strcmp(sb->s_type->name, "debugfs") ||
!strcmp(sb->s_type->name, "tracefs") ||
Expand All @@ -509,6 +503,34 @@ static int selinux_is_sblabel_mnt(struct super_block *sb)
!strcmp(sb->s_type->name, "cgroup2")));
}

static int selinux_is_sblabel_mnt(struct super_block *sb)
{
struct superblock_security_struct *sbsec = sb->s_security;

/*
* IMPORTANT: Double-check logic in this function when adding a new
* SECURITY_FS_USE_* definition!
*/
BUILD_BUG_ON(SECURITY_FS_USE_MAX != 7);

switch (sbsec->behavior) {
case SECURITY_FS_USE_XATTR:
case SECURITY_FS_USE_TRANS:
case SECURITY_FS_USE_TASK:
case SECURITY_FS_USE_NATIVE:
return 1;

case SECURITY_FS_USE_GENFS:
return selinux_is_genfs_special_handling(sb);

/* Never allow relabeling on context mounts */
case SECURITY_FS_USE_MNTPOINT:
case SECURITY_FS_USE_NONE:
default:
return 0;
}
}

static int sb_finish_set_opts(struct super_block *sb)
{
struct superblock_security_struct *sbsec = sb->s_security;
Expand Down Expand Up @@ -2881,9 +2903,8 @@ static int selinux_inode_follow_link(struct dentry *dentry, struct inode *inode,
if (IS_ERR(isec))
return PTR_ERR(isec);

return avc_has_perm_flags(&selinux_state,
sid, isec->sid, isec->sclass, FILE__READ, &ad,
rcu ? MAY_NOT_BLOCK : 0);
return avc_has_perm(&selinux_state,
sid, isec->sid, isec->sclass, FILE__READ, &ad);
}

static noinline int audit_inode_permission(struct inode *inode,
Expand Down Expand Up @@ -2938,7 +2959,9 @@ static int selinux_inode_permission(struct inode *inode, int mask)
return PTR_ERR(isec);

rc = avc_has_perm_noaudit(&selinux_state,
sid, isec->sid, isec->sclass, perms, 0, &avd);
sid, isec->sid, isec->sclass, perms,
(flags & MAY_NOT_BLOCK) ? AVC_NONBLOCKING : 0,
&avd);
audited = avc_audit_required(perms, &avd, rc,
from_access ? FILE__AUDIT_ACCESS : 0,
&denied);
Expand Down Expand Up @@ -3197,12 +3220,16 @@ static int selinux_inode_setsecurity(struct inode *inode, const char *name,
const void *value, size_t size, int flags)
{
struct inode_security_struct *isec = inode_security_novalidate(inode);
struct superblock_security_struct *sbsec = inode->i_sb->s_security;
u32 newsid;
int rc;

if (strcmp(name, XATTR_SELINUX_SUFFIX))
return -EOPNOTSUPP;

if (!(sbsec->flags & SBLABEL_MNT))
return -EOPNOTSUPP;

if (!value || !size)
return -EACCES;

Expand Down Expand Up @@ -6236,7 +6263,10 @@ static void selinux_inode_invalidate_secctx(struct inode *inode)
*/
static int selinux_inode_notifysecctx(struct inode *inode, void *ctx, u32 ctxlen)
{
return selinux_inode_setsecurity(inode, XATTR_SELINUX_SUFFIX, ctx, ctxlen, 0);
int rc = selinux_inode_setsecurity(inode, XATTR_SELINUX_SUFFIX,
ctx, ctxlen, 0);
/* Do not return error when suppressing label (SBLABEL_MNT not set). */
return rc == -EOPNOTSUPP ? 0 : rc;
}

/*
Expand Down
6 changes: 1 addition & 5 deletions security/selinux/include/avc.h
View file
Original file line number Diff line number Diff line change
Expand Up @@ -142,6 +142,7 @@ static inline int avc_audit(struct selinux_state *state,

#define AVC_STRICT 1 /* Ignore permissive mode. */
#define AVC_EXTENDED_PERMS 2 /* update extended permissions */
#define AVC_NONBLOCKING 4 /* non blocking */
int avc_has_perm_noaudit(struct selinux_state *state,
u32 ssid, u32 tsid,
u16 tclass, u32 requested,
Expand All @@ -152,11 +153,6 @@ int avc_has_perm(struct selinux_state *state,
u32 ssid, u32 tsid,
u16 tclass, u32 requested,
struct common_audit_data *auditdata);
int avc_has_perm_flags(struct selinux_state *state,
u32 ssid, u32 tsid,
u16 tclass, u32 requested,
struct common_audit_data *auditdata,
int flags);

int avc_has_extended_perms(struct selinux_state *state,
u32 ssid, u32 tsid, u16 tclass, u32 requested,
Expand Down
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