[PATCH 5.11 012/210] selinux: fix cond_list corruption when changing booleans

Greg Kroah-Hartman
2021-04-12T09:31:03Z

From: Ondrej Mosnacek <omosnace@redhat.com>

commit d8f5f0ea5b86300390b026b6c6e7836b7150814a upstream.

Currently, duplicate_policydb_cond_list() first copies the whole
conditional avtab and then tries to link to the correct entries in
cond_dup_av_list() using avtab_search(). However, since the conditional
avtab may contain multiple entries with the same key, this approach
often fails to find the right entry, potentially leading to wrong rules
being activated/deactivated when booleans are changed.

To fix this, instead start with an empty conditional avtab and add the
individual entries one-by-one while building the new av_lists. This
approach leads to the correct result, since each entry is present in the
av_lists exactly once.

The issue can be reproduced with Fedora policy as follows:

# sesearch -s ftpd_t -t public_content_rw_t -c dir -p create -A
allow ftpd_t non_security_file_type:dir { add_name create getattr ioctl link lock open read remove_name rename reparent rmdir search setattr unlink watch watch_reads write }; [ ftpd_full_access ]:True
allow ftpd_t public_content_rw_t:dir { add_name create link remove_name rename reparent rmdir setattr unlink watch watch_reads write }; [ ftpd_anon_write ]:True
# setsebool ftpd_anon_write=off ftpd_connect_all_unreserved=off ftpd_connect_db=off ftpd_full_access=off

On fixed kernels, the sesearch output is the same after the setsebool
command:

# sesearch -s ftpd_t -t public_content_rw_t -c dir -p create -A
allow ftpd_t non_security_file_type:dir { add_name create getattr ioctl link lock open read remove_name rename reparent rmdir search setattr unlink watch watch_reads write }; [ ftpd_full_access ]:True
allow ftpd_t public_content_rw_t:dir { add_name create link remove_name rename reparent rmdir setattr unlink watch watch_reads write }; [ ftpd_anon_write ]:True

While on the broken kernels, it will be different:

# sesearch -s ftpd_t -t public_content_rw_t -c dir -p create -A
allow ftpd_t non_security_file_type:dir { add_name create getattr ioctl link lock open read remove_name rename reparent rmdir search setattr unlink watch watch_reads write }; [ ftpd_full_access ]:True
allow ftpd_t non_security_file_type:dir { add_name create getattr ioctl link lock open read remove_name rename reparent rmdir search setattr unlink watch watch_reads write }; [ ftpd_full_access ]:True
allow ftpd_t non_security_file_type:dir { add_name create getattr ioctl link lock open read remove_name rename reparent rmdir search setattr unlink watch watch_reads write }; [ ftpd_full_access ]:True

While there, also simplify the computation of nslots. This changes the
nslots values for nrules 2 or 3 to just two slots instead of 4, which
makes the sequence more consistent.

Cc: stable@vger.kernel.org
Fixes: c7c556f1e81b ("selinux: refactor changing booleans")
Signed-off-by: Ondrej Mosnacek <omosnace@redhat.com>
Signed-off-by: Paul Moore <paul@paul-moore.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
security/selinux/ss/avtab.c | 86 +++++++++++---------------------------
security/selinux/ss/avtab.h | 2
security/selinux/ss/conditional.c | 12 ++---
3 files changed, 32 insertions(+), 68 deletions(-)

--- a/security/selinux/ss/avtab.c
+++ b/security/selinux/ss/avtab.c
@@ -308,24 +308,10 @@ void avtab_init(struct avtab *h)
h->mask = 0;
}

-int avtab_alloc(struct avtab *h, u32 nrules)
+static int avtab_alloc_common(struct avtab *h, u32 nslot)
{
- u32 shift = 0;
- u32 work = nrules;
- u32 nslot;
-
- if (nrules == 0)
- goto avtab_alloc_out;
-
- while (work) {
- work = work >> 1;
- shift++;
- }
- if (shift > 2)
- shift = shift - 2;
- nslot = 1 << shift;
- if (nslot > MAX_AVTAB_HASH_BUCKETS)
- nslot = MAX_AVTAB_HASH_BUCKETS;
+ if (!nslot)
+ return 0;

h->htable = kvcalloc(nslot, sizeof(void *), GFP_KERNEL);
if (!h->htable)
@@ -333,59 +319,37 @@ int avtab_alloc(struct avtab *h, u32 nru

h->nslot = nslot;
h->mask = nslot - 1;
-
-avtab_alloc_out:
- pr_debug("SELinux: %d avtab hash slots, %d rules.\n",
- h->nslot, nrules);
return 0;
}

-int avtab_duplicate(struct avtab *new, struct avtab *orig)
+int avtab_alloc(struct avtab *h, u32 nrules)
{
- int i;
- struct avtab_node *node, *tmp, *tail;
-
- memset(new, 0, sizeof(*new));
+ int rc;
+ u32 nslot = 0;

- new->htable = kvcalloc(orig->nslot, sizeof(void *), GFP_KERNEL);
- if (!new->htable)
- return -ENOMEM;
- new->nslot = orig->nslot;
- new->mask = orig->mask;
-
- for (i = 0; i < orig->nslot; i++) {
- tail = NULL;
- for (node = orig->htable[i]; node; node = node->next) {
- tmp = kmem_cache_zalloc(avtab_node_cachep, GFP_KERNEL);
- if (!tmp)
- goto error;
- tmp->key = node->key;
- if (tmp->key.specified & AVTAB_XPERMS) {
- tmp->datum.u.xperms =
- kmem_cache_zalloc(avtab_xperms_cachep,
- GFP_KERNEL);
- if (!tmp->datum.u.xperms) {
- kmem_cache_free(avtab_node_cachep, tmp);
- goto error;
- }
- tmp->datum.u.xperms = node->datum.u.xperms;
- } else
- tmp->datum.u.data = node->datum.u.data;
-
- if (tail)
- tail->next = tmp;
- else
- new->htable[i] = tmp;
-
- tail = tmp;
- new->nel++;
+ if (nrules != 0) {
+ u32 shift = 1;
+ u32 work = nrules >> 3;
+ while (work) {
+ work >>= 1;
+ shift++;
}
+ nslot = 1 << shift;
+ if (nslot > MAX_AVTAB_HASH_BUCKETS)
+ nslot = MAX_AVTAB_HASH_BUCKETS;
+
+ rc = avtab_alloc_common(h, nslot);
+ if (rc)
+ return rc;
}

+ pr_debug("SELinux: %d avtab hash slots, %d rules.\n", nslot, nrules);
return 0;
-error:
- avtab_destroy(new);
- return -ENOMEM;
+}
+
+int avtab_alloc_dup(struct avtab *new, const struct avtab *orig)
+{
+ return avtab_alloc_common(new, orig->nslot);
}

void avtab_hash_eval(struct avtab *h, char *tag)
--- a/security/selinux/ss/avtab.h
+++ b/security/selinux/ss/avtab.h
@@ -89,7 +89,7 @@ struct avtab {

void avtab_init(struct avtab *h);
int avtab_alloc(struct avtab *, u32);
-int avtab_duplicate(struct avtab *new, struct avtab *orig);
+int avtab_alloc_dup(struct avtab *new, const struct avtab *orig);
struct avtab_datum *avtab_search(struct avtab *h, struct avtab_key *k);
void avtab_destroy(struct avtab *h);
void avtab_hash_eval(struct avtab *h, char *tag);
--- a/security/selinux/ss/conditional.c
+++ b/security/selinux/ss/conditional.c
@@ -605,7 +605,6 @@ static int cond_dup_av_list(struct cond_
struct cond_av_list *orig,
struct avtab *avtab)
{
- struct avtab_node *avnode;
u32 i;

memset(new, 0, sizeof(*new));
@@ -615,10 +614,11 @@ static int cond_dup_av_list(struct cond_
return -ENOMEM;

for (i = 0; i < orig->len; i++) {
- avnode = avtab_search_node(avtab, &orig->nodes[i]->key);
- if (WARN_ON(!avnode))
- return -EINVAL;
- new->nodes[i] = avnode;
+ new->nodes[i] = avtab_insert_nonunique(avtab,
+ &orig->nodes[i]->key,
+ &orig->nodes[i]->datum);
+ if (!new->nodes[i])
+ return -ENOMEM;
new->len++;
}

@@ -630,7 +630,7 @@ static int duplicate_policydb_cond_list(
{
int rc, i, j;

- rc = avtab_duplicate(&newp->te_cond_avtab, &origp->te_cond_avtab);
+ rc = avtab_alloc_dup(&newp->te_cond_avtab, &origp->te_cond_avtab);
if (rc)
return rc;