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apparmor: Remove use of the double lock

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The use of the double lock is not necessary and problematic. Instead
pull the bits that need locks into their own sections and grab the
needed references.

Fixes: c05e705812 ("apparmor: add fine grained af_unix mediation")
Signed-off-by: John Johansen <john.johansen@canonical.com>
This commit is contained in:
John Johansen
2025-04-01 15:28:13 -07:00
parent 6afb0a7bc9
commit bc6e5f6933
5 changed files with 104 additions and 102 deletions
Download Patch File Download Diff File Expand all files Collapse all files

197
security/apparmor/af_unix.c
View File

@@ -30,11 +30,10 @@ static inline struct sock *aa_unix_sk(struct unix_sock *u)
}
static int unix_fs_perm(const char *op, u32 mask, const struct cred *subj_cred,
struct aa_label *label, struct unix_sock *u)
struct aa_label *label, struct path *path)
{
AA_BUG(!label);
AA_BUG(!u);
AA_BUG(!is_unix_fs(aa_unix_sk(u)));
AA_BUG(!path);
if (unconfined(label) || !label_mediates(label, AA_CLASS_FILE))
return 0;
@@ -43,13 +42,13 @@ static int unix_fs_perm(const char *op, u32 mask, const struct cred *subj_cred,
/* if !u->path.dentry socket is being shutdown - implicit delegation
* until obj delegation is supported
*/
if (u->path.dentry) {
if (path->dentry) {
/* the sunpath may not be valid for this ns so use the path */
struct path_cond cond = { u->path.dentry->d_inode->i_uid,
u->path.dentry->d_inode->i_mode
struct path_cond cond = { path->dentry->d_inode->i_uid,
path->dentry->d_inode->i_mode
};
return aa_path_perm(op, subj_cred, label, &u->path,
return aa_path_perm(op, subj_cred, label, path,
PATH_SOCK_COND, mask, &cond);
} /* else implicitly delegated */
@@ -102,18 +101,27 @@ static aa_state_t match_to_local(struct aa_policydb *policy,
return state;
}
struct sockaddr_un *aa_sunaddr(const struct unix_sock *u, int *addrlen)
{
struct unix_address *addr;
/* memory barrier is sufficient see note in net/unix/af_unix.c */
addr = smp_load_acquire(&u->addr);
if (addr) {
*addrlen = addr->len;
return addr->name;
}
*addrlen = 0;
return NULL;
}
static aa_state_t match_to_sk(struct aa_policydb *policy,
aa_state_t state, u32 request,
struct unix_sock *u, struct aa_perms **p,
const char **info)
{
struct sockaddr_un *addr = NULL;
int addrlen = 0;
if (u->addr) {
addr = u->addr->name;
addrlen = u->addr->len;
}
int addrlen;
struct sockaddr_un *addr = aa_sunaddr(u, &addrlen);
return match_to_local(policy, state, request, u->sk.sk_type,
u->sk.sk_protocol, addr, addrlen, p, info);
@@ -363,7 +371,8 @@ static int profile_opt_perm(struct aa_profile *profile, u32 request,
/* null peer_label is allowed, in which case the peer_sk label is used */
static int profile_peer_perm(struct aa_profile *profile, u32 request,
struct sock *sk, struct sock *peer_sk,
struct sock *sk, struct sockaddr_un *peer_addr,
int peer_addrlen,
struct aa_label *peer_label,
struct apparmor_audit_data *ad)
{
@@ -375,26 +384,16 @@ static int profile_peer_perm(struct aa_profile *profile, u32 request,
AA_BUG(!profile);
AA_BUG(profile_unconfined(profile));
AA_BUG(!sk);
AA_BUG(!peer_sk);
AA_BUG(!peer_label);
AA_BUG(!ad);
AA_BUG(is_unix_fs(peer_sk)); /* currently always calls unix_fs_perm */
state = RULE_MEDIATES_v9NET(rules);
if (state) {
struct aa_sk_ctx *peer_ctx = aa_sock(peer_sk);
struct aa_profile *peerp;
struct sockaddr_un *addr = NULL;
int len = 0;
if (unix_sk(peer_sk)->addr) {
addr = unix_sk(peer_sk)->addr->name;
len = unix_sk(peer_sk)->addr->len;
}
state = match_to_peer(rules->policy, state, request,
unix_sk(sk),
addr, len, &p, &ad->info);
if (!peer_label)
peer_label = peer_ctx->label;
peer_addr, peer_addrlen, &p, &ad->info);
return fn_for_each_in_ns(peer_label, peerp,
match_label(profile, rules, state, request,
@@ -422,9 +421,8 @@ int aa_unix_create_perm(struct aa_label *label, int family, int type,
return 0;
}
int aa_unix_label_sk_perm(const struct cred *subj_cred,
struct aa_label *label, const char *op, u32 request,
struct sock *sk)
int aa_unix_label_sk_perm(const struct cred *subj_cred, struct aa_label *label,
const char *op, u32 request, struct sock *sk)
{
if (!unconfined(label)) {
struct aa_profile *profile;
@@ -436,19 +434,6 @@ int aa_unix_label_sk_perm(const struct cred *subj_cred,
return 0;
}
static int unix_label_sock_perm(const struct cred *subj_cred,
struct aa_label *label, const char *op,
u32 request, struct socket *sock)
{
if (unconfined(label))
return 0;
if (is_unix_fs(sock->sk))
return unix_fs_perm(op, request, subj_cred, label,
unix_sk(sock->sk));
return aa_unix_label_sk_perm(subj_cred, label, op, request, sock->sk);
}
/* revalidation, get/set attr, shutdown */
int aa_unix_sock_perm(const char *op, u32 request, struct socket *sock)
{
@@ -456,7 +441,12 @@ int aa_unix_sock_perm(const char *op, u32 request, struct socket *sock)
int error;
label = begin_current_label_crit_section();
error = unix_label_sock_perm(current_cred(), label, op, request, sock);
if (is_unix_fs(sock->sk))
error = unix_fs_perm(op, request, current_cred(), label,
&unix_sk(sock->sk)->path);
else
error = aa_unix_label_sk_perm(current_cred(), label, op,
request, sock->sk);
end_current_label_crit_section(label);
return error;
@@ -464,7 +454,7 @@ int aa_unix_sock_perm(const char *op, u32 request, struct socket *sock)
static int valid_addr(struct sockaddr *addr, int addr_len)
{
struct sockaddr_un *sunaddr = (struct sockaddr_un *)addr;
struct sockaddr_un *sunaddr = unix_addr(addr);
/* addr_len == offsetof(struct sockaddr_un, sun_path) is autobind */
if (addr_len < offsetof(struct sockaddr_un, sun_path) ||
@@ -586,6 +576,22 @@ int aa_unix_opt_perm(const char *op, u32 request, struct socket *sock,
return error;
}
static int unix_peer_perm(const struct cred *subj_cred,
struct aa_label *label, const char *op, u32 request,
struct sock *sk, struct sockaddr_un *peer_addr,
int peer_addrlen, struct aa_label *peer_label)
{
struct aa_profile *profile;
DEFINE_AUDIT_SK(ad, op, subj_cred, sk);
ad.net.addr = peer_addr;
ad.net.addrlen = peer_addrlen;
return fn_for_each_confined(label, profile,
profile_peer_perm(profile, request, sk,
peer_addr, peer_addrlen, peer_label, &ad));
}
/**
*
* Requires: lock held on both @sk and @peer_sk
@@ -602,58 +608,37 @@ int aa_unix_peer_perm(const struct cred *subj_cred,
AA_BUG(!label);
AA_BUG(!sk);
AA_BUG(!peer_sk);
AA_BUG(!peer_label);
if (is_unix_fs(aa_unix_sk(peeru))) {
return unix_fs_perm(op, request, subj_cred, label, peeru);
return unix_fs_perm(op, request, subj_cred, label,
&peeru->path);
} else if (is_unix_fs(aa_unix_sk(u))) {
return unix_fs_perm(op, request, subj_cred, label, u);
return unix_fs_perm(op, request, subj_cred, label, &u->path);
} else if (!unconfined(label)) {
struct aa_profile *profile;
DEFINE_AUDIT_SK(ad, op, subj_cred, sk);
int plen;
struct sockaddr_un *paddr = aa_sunaddr(unix_sk(peer_sk),
&plen);
ad.net.peer_sk = peer_sk;
return fn_for_each_confined(label, profile,
profile_peer_perm(profile, request, sk,
peer_sk, peer_label, &ad));
return unix_peer_perm(subj_cred, label, op, request,
sk, paddr, plen, peer_label);
}
return 0;
}
static void unix_state_double_lock(struct sock *sk1, struct sock *sk2)
{
if (unlikely(sk1 == sk2) || !sk2) {
unix_state_lock(sk1);
return;
}
if (sk1 < sk2) {
unix_state_lock(sk1);
unix_state_lock(sk2);
} else {
unix_state_lock(sk2);
unix_state_lock(sk1);
}
}
static void unix_state_double_unlock(struct sock *sk1, struct sock *sk2)
{
if (unlikely(sk1 == sk2) || !sk2) {
unix_state_unlock(sk1);
return;
}
unix_state_unlock(sk1);
unix_state_unlock(sk2);
}
/* TODO: examine replacing double lock with cached addr */
/* This fn is only checked if something has changed in the security
* boundaries. Otherwise cached info off file is sufficient
*/
int aa_unix_file_perm(const struct cred *subj_cred, struct aa_label *label,
const char *op, u32 request, struct file *file)
{
struct socket *sock = (struct socket *) file->private_data;
struct sockaddr_un *addr, *peer_addr;
int addrlen, peer_addrlen;
struct sock *peer_sk = NULL;
u32 sk_req = request & ~NET_PEER_MASK;
struct path path;
bool is_sk_fs;
int error = 0;
@@ -663,40 +648,60 @@ int aa_unix_file_perm(const struct cred *subj_cred, struct aa_label *label,
AA_BUG(sock->sk->sk_family != PF_UNIX);
/* TODO: update sock label with new task label */
/* investigate only using lock via unix_peer_get()
* addr only needs the memory barrier, but need to investigate
* path
*/
unix_state_lock(sock->sk);
peer_sk = unix_peer(sock->sk);
if (peer_sk)
sock_hold(peer_sk);
is_sk_fs = is_unix_fs(sock->sk);
addr = aa_sunaddr(unix_sk(sock->sk), &addrlen);
path = unix_sk(sock->sk)->path;
unix_state_unlock(sock->sk);
if (is_sk_fs && peer_sk)
sk_req = request;
if (sk_req)
error = unix_label_sock_perm(subj_cred, label, op, sk_req,
sock);
unix_state_unlock(sock->sk);
if (sk_req) {
if (is_sk_fs)
error = unix_fs_perm(op, sk_req, subj_cred, label,
&path);
else
error = aa_unix_label_sk_perm(subj_cred, label, op,
sk_req, sock->sk);
}
if (!peer_sk)
return error;
goto out;
unix_state_double_lock(sock->sk, peer_sk);
peer_addr = aa_sunaddr(unix_sk(peer_sk), &peer_addrlen);
struct path peer_path;
peer_path = unix_sk(peer_sk)->path;
if (!is_sk_fs && is_unix_fs(peer_sk)) {
last_error(error,
unix_fs_perm(op, request, subj_cred, label,
unix_sk(peer_sk)));
&peer_path));
} else if (!is_sk_fs) {
struct aa_sk_ctx *pctx = aa_sock(peer_sk);
/* no fs check of aa_unix_peer_perm because conditions above
* ensure they will never be done
*/
last_error(error,
xcheck(aa_unix_peer_perm(subj_cred, label, op,
MAY_READ | MAY_WRITE,
sock->sk, peer_sk, NULL),
aa_unix_peer_perm(file->f_cred, pctx->label, op,
MAY_READ | MAY_WRITE,
peer_sk, sock->sk, label)));
xcheck(unix_peer_perm(subj_cred, label, op,
MAY_READ | MAY_WRITE, sock->sk,
peer_addr, peer_addrlen,
pctx->label),
unix_peer_perm(file->f_cred, pctx->label, op,
MAY_READ | MAY_WRITE, peer_sk,
addr, addrlen, label)));
}
unix_state_double_unlock(sock->sk, peer_sk);
sock_put(peer_sk);
out:
return error;
}

1
security/apparmor/include/af_unix.h
View File

@@ -31,6 +31,7 @@
#define is_unix_connected(S) ((S)->state == SS_CONNECTED)
struct sockaddr_un *aa_sunaddr(const struct unix_sock *u, int *addrlen);
int aa_unix_peer_perm(const struct cred *subj_cred,
struct aa_label *label, const char *op, u32 request,
struct sock *sk, struct sock *peer_sk,

1
security/apparmor/include/audit.h
View File

@@ -138,7 +138,6 @@ struct apparmor_audit_data {
};
struct {
int type, protocol;
struct sock *peer_sk;
void *addr;
int addrlen;
} net;

4
security/apparmor/lsm.c
View File

@@ -1112,7 +1112,7 @@ static int unix_connect_perm(const struct cred *cred, struct aa_label *label,
error = aa_unix_peer_perm(cred, label, OP_CONNECT,
(AA_MAY_CONNECT | AA_MAY_SEND | AA_MAY_RECEIVE),
sk, peer_sk, NULL);
sk, peer_sk, peer_ctx->label);
if (!is_unix_fs(peer_sk)) {
last_error(error,
aa_unix_peer_perm(cred,
@@ -1184,7 +1184,7 @@ static int apparmor_unix_may_send(struct socket *sock, struct socket *peer)
label = __begin_current_label_crit_section(&needput);
error = xcheck(aa_unix_peer_perm(current_cred(),
label, OP_SENDMSG, AA_MAY_SEND,
sock->sk, peer->sk, NULL),
sock->sk, peer->sk, peer_ctx->label),
aa_unix_peer_perm(peer->file ? peer->file->f_cred : NULL,
peer_ctx->label, OP_SENDMSG,
AA_MAY_RECEIVE,

3
security/apparmor/net.c
View File

@@ -148,9 +148,6 @@ void audit_net_cb(struct audit_buffer *ab, void *va)
audit_unix_addr(ab, "peer_addr",
unix_addr(ad->net.addr),
ad->net.addrlen);
else
audit_unix_sk_addr(ab, "peer_addr",
ad->net.peer_sk);
}
}
if (ad->peer) {