kbuild: rust: keep Rust objects out of Clang LTO with inline helpersgrafted

Under `CONFIG_LTO_CLANG` + `CONFIG_RUST_INLINE_HELPERS`, one may hit
`objtool` errors such as:

    vmlinux.o: error: objtool: _R..._3Gsp4boot+0xd6a:
    can't find jump dest instruction at .text._R..._3Gsp4boot+0x1dfd

The reason is that in such builds, the Clang invocation that compiles
the combined Rust plus helpers bitcode emits LLVM bitcode (again) --
the final code generation happens in the linker's LTO step, which the
`-mllvm` trap options passed to Clang do not reach.

This, in turn, means that unreachable traps are missing, and the
impossible paths do not merely fallthrough to the next symbol, but past
the end of their own section, since LTO builds place each function in
its own section.

Thus filter `CC_FLAGS_LTO` out of the Clang invocation, so that it always
emits machine code directly, with the traps in place.

Assisted-by: LLM
Cc: Gary Guo <gary@garyguo.net>
Cc: Boqun Feng <boqun@kernel.org>
Cc: Alice Ryhl <aliceryhl@google.com>
Cc: Matthew Maurer <mmaurer@google.com>
Cc: Josh Poimboeuf <jpoimboe@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: stable@vger.kernel.org
Fixes: 3a2486cc1da5 ("kbuild: rust: provide an option to inline C helpers into Rust")
Acked-by: Gary Guo <gary@garyguo.net>
Link: https://patch.msgid.link/20260816133233.197500-2-ojeda@kernel.org
Signed-off-by: Miguel Ojeda <ojeda@kernel.org>

1 files changed, 457 insertions, 0 deletions

diff --git a/security/lsm_audit.c b/security/lsm_audit.c
new file mode 100644
index 000000000..737f5a263
--- /dev/null
+++ b/security/lsm_audit.c
@@ -0,0 +1,457 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * common LSM auditing functions
+ *
+ * Based on code written for SELinux by :
+ *			Stephen Smalley
+ * 			James Morris <jmorris@redhat.com>
+ * Author : Etienne Basset, <etienne.basset@ensta.org>
+ */
+
+#include <linux/types.h>
+#include <linux/stddef.h>
+#include <linux/kernel.h>
+#include <linux/gfp.h>
+#include <linux/fs.h>
+#include <linux/init.h>
+#include <net/sock.h>
+#include <linux/un.h>
+#include <net/af_unix.h>
+#include <linux/audit.h>
+#include <linux/ipv6.h>
+#include <linux/ip.h>
+#include <net/ip.h>
+#include <net/ipv6.h>
+#include <linux/tcp.h>
+#include <linux/udp.h>
+#include <linux/sctp.h>
+#include <linux/lsm_audit.h>
+#include <linux/security.h>
+
+/**
+ * ipv4_skb_to_auditdata : fill auditdata from skb
+ * @skb : the skb
+ * @ad : the audit data to fill
+ * @proto : the layer 4 protocol
+ *
+ * return  0 on success
+ */
+int ipv4_skb_to_auditdata(struct sk_buff *skb,
+		struct common_audit_data *ad, u8 *proto)
+{
+	int ret = 0;
+	struct iphdr *ih;
+
+	ih = ip_hdr(skb);
+	ad->u.net->v4info.saddr = ih->saddr;
+	ad->u.net->v4info.daddr = ih->daddr;
+
+	if (proto)
+		*proto = ih->protocol;
+	/* non initial fragment */
+	if (ntohs(ih->frag_off) & IP_OFFSET)
+		return 0;
+
+	switch (ih->protocol) {
+	case IPPROTO_TCP: {
+		struct tcphdr *th = tcp_hdr(skb);
+
+		ad->u.net->sport = th->source;
+		ad->u.net->dport = th->dest;
+		break;
+	}
+	case IPPROTO_UDP: {
+		struct udphdr *uh = udp_hdr(skb);
+
+		ad->u.net->sport = uh->source;
+		ad->u.net->dport = uh->dest;
+		break;
+	}
+	case IPPROTO_SCTP: {
+		struct sctphdr *sh = sctp_hdr(skb);
+
+		ad->u.net->sport = sh->source;
+		ad->u.net->dport = sh->dest;
+		break;
+	}
+	default:
+		ret = -EINVAL;
+	}
+	return ret;
+}
+#if IS_ENABLED(CONFIG_IPV6)
+/**
+ * ipv6_skb_to_auditdata : fill auditdata from skb
+ * @skb : the skb
+ * @ad : the audit data to fill
+ * @proto : the layer 4 protocol
+ *
+ * return  0 on success
+ */
+int ipv6_skb_to_auditdata(struct sk_buff *skb,
+		struct common_audit_data *ad, u8 *proto)
+{
+	int offset, ret = 0;
+	struct ipv6hdr *ip6;
+	u8 nexthdr;
+	__be16 frag_off;
+
+	ip6 = ipv6_hdr(skb);
+	ad->u.net->v6info.saddr = ip6->saddr;
+	ad->u.net->v6info.daddr = ip6->daddr;
+	/* IPv6 can have several extension header before the Transport header
+	 * skip them */
+	offset = skb_network_offset(skb);
+	offset += sizeof(*ip6);
+	nexthdr = ip6->nexthdr;
+	offset = ipv6_skip_exthdr(skb, offset, &nexthdr, &frag_off);
+	if (offset < 0)
+		return 0;
+	if (proto)
+		*proto = nexthdr;
+	switch (nexthdr) {
+	case IPPROTO_TCP: {
+		struct tcphdr _tcph, *th;
+
+		th = skb_header_pointer(skb, offset, sizeof(_tcph), &_tcph);
+		if (th == NULL)
+			break;
+
+		ad->u.net->sport = th->source;
+		ad->u.net->dport = th->dest;
+		break;
+	}
+	case IPPROTO_UDP: {
+		struct udphdr _udph, *uh;
+
+		uh = skb_header_pointer(skb, offset, sizeof(_udph), &_udph);
+		if (uh == NULL)
+			break;
+
+		ad->u.net->sport = uh->source;
+		ad->u.net->dport = uh->dest;
+		break;
+	}
+	case IPPROTO_SCTP: {
+		struct sctphdr _sctph, *sh;
+
+		sh = skb_header_pointer(skb, offset, sizeof(_sctph), &_sctph);
+		if (sh == NULL)
+			break;
+		ad->u.net->sport = sh->source;
+		ad->u.net->dport = sh->dest;
+		break;
+	}
+	default:
+		ret = -EINVAL;
+	}
+	return ret;
+}
+#endif
+
+
+static inline void print_ipv6_addr(struct audit_buffer *ab,
+				   const struct in6_addr *addr, __be16 port,
+				   const char *name1, const char *name2)
+{
+	if (!ipv6_addr_any(addr))
+		audit_log_format(ab, " %s=%pI6c", name1, addr);
+	if (port)
+		audit_log_format(ab, " %s=%d", name2, ntohs(port));
+}
+
+static inline void print_ipv4_addr(struct audit_buffer *ab, __be32 addr,
+				   __be16 port, const char *name1, const char *name2)
+{
+	if (addr)
+		audit_log_format(ab, " %s=%pI4", name1, &addr);
+	if (port)
+		audit_log_format(ab, " %s=%d", name2, ntohs(port));
+}
+
+/**
+ * audit_log_lsm_data - helper to log common LSM audit data
+ * @ab : the audit buffer
+ * @a : common audit data
+ */
+void audit_log_lsm_data(struct audit_buffer *ab,
+			const struct common_audit_data *a)
+{
+	/*
+	 * To keep stack sizes in check force programmers to notice if they
+	 * start making this union too large!  See struct lsm_network_audit
+	 * as an example of how to deal with large data.
+	 */
+	BUILD_BUG_ON(sizeof(a->u) > sizeof(void *)*2);
+
+	switch (a->type) {
+	case LSM_AUDIT_DATA_NONE:
+		return;
+	case LSM_AUDIT_DATA_IPC:
+		audit_log_format(ab, " ipc_key=%d ", a->u.ipc_id);
+		break;
+	case LSM_AUDIT_DATA_CAP:
+		audit_log_format(ab, " capability=%d ", a->u.cap);
+		break;
+	case LSM_AUDIT_DATA_PATH: {
+		struct inode *inode;
+
+		audit_log_d_path(ab, " path=", &a->u.path);
+
+		inode = d_backing_inode(a->u.path.dentry);
+		if (inode) {
+			audit_log_format(ab, " dev=");
+			audit_log_untrustedstring(ab, inode->i_sb->s_id);
+			audit_log_format(ab, " ino=%llu", inode->i_ino);
+		}
+		break;
+	}
+	case LSM_AUDIT_DATA_FILE: {
+		struct inode *inode;
+
+		audit_log_d_path(ab, " path=", &a->u.file->f_path);
+
+		inode = file_inode(a->u.file);
+		if (inode) {
+			audit_log_format(ab, " dev=");
+			audit_log_untrustedstring(ab, inode->i_sb->s_id);
+			audit_log_format(ab, " ino=%llu", inode->i_ino);
+		}
+		break;
+	}
+	case LSM_AUDIT_DATA_IOCTL_OP: {
+		struct inode *inode;
+
+		audit_log_d_path(ab, " path=", &a->u.op->path);
+
+		inode = a->u.op->path.dentry->d_inode;
+		if (inode) {
+			audit_log_format(ab, " dev=");
+			audit_log_untrustedstring(ab, inode->i_sb->s_id);
+			audit_log_format(ab, " ino=%llu", inode->i_ino);
+		}
+
+		audit_log_format(ab, " ioctlcmd=0x%hx", a->u.op->cmd);
+		break;
+	}
+	case LSM_AUDIT_DATA_DENTRY: {
+		struct inode *inode;
+
+		audit_log_format(ab, " name=");
+		spin_lock(&a->u.dentry->d_lock);
+		audit_log_untrustedstring(ab, a->u.dentry->d_name.name);
+		spin_unlock(&a->u.dentry->d_lock);
+
+		inode = d_backing_inode(a->u.dentry);
+		if (inode) {
+			audit_log_format(ab, " dev=");
+			audit_log_untrustedstring(ab, inode->i_sb->s_id);
+			audit_log_format(ab, " ino=%llu", inode->i_ino);
+		}
+		break;
+	}
+	case LSM_AUDIT_DATA_INODE: {
+		struct dentry *dentry;
+		struct inode *inode;
+
+		rcu_read_lock();
+		inode = a->u.inode;
+		dentry = d_find_alias_rcu(inode);
+		if (dentry) {
+			audit_log_format(ab, " name=");
+			spin_lock(&dentry->d_lock);
+			audit_log_untrustedstring(ab, dentry->d_name.name);
+			spin_unlock(&dentry->d_lock);
+		}
+		audit_log_format(ab, " dev=");
+		audit_log_untrustedstring(ab, inode->i_sb->s_id);
+		audit_log_format(ab, " ino=%llu", inode->i_ino);
+		rcu_read_unlock();
+		break;
+	}
+	case LSM_AUDIT_DATA_TASK: {
+		struct task_struct *tsk = a->u.tsk;
+		if (tsk) {
+			pid_t pid = task_tgid_nr(tsk);
+			if (pid) {
+				char tskcomm[sizeof(tsk->comm)];
+				audit_log_format(ab, " opid=%d ocomm=", pid);
+				audit_log_untrustedstring(ab,
+				    get_task_comm(tskcomm, tsk));
+			}
+		}
+		break;
+	}
+	case LSM_AUDIT_DATA_NET:
+		if (a->u.net->sk) {
+			const struct sock *sk = a->u.net->sk;
+			const struct unix_sock *u;
+			struct unix_address *addr;
+			int len = 0;
+			char *p = NULL;
+
+			switch (sk->sk_family) {
+			case AF_INET: {
+				const struct inet_sock *inet = inet_sk(sk);
+
+				print_ipv4_addr(ab, inet->inet_rcv_saddr,
+						inet->inet_sport,
+						"laddr", "lport");
+				print_ipv4_addr(ab, inet->inet_daddr,
+						inet->inet_dport,
+						"faddr", "fport");
+				break;
+			}
+#if IS_ENABLED(CONFIG_IPV6)
+			case AF_INET6: {
+				const struct inet_sock *inet = inet_sk(sk);
+
+				print_ipv6_addr(ab, &sk->sk_v6_rcv_saddr,
+						inet->inet_sport,
+						"laddr", "lport");
+				print_ipv6_addr(ab, &sk->sk_v6_daddr,
+						inet->inet_dport,
+						"faddr", "fport");
+				break;
+			}
+#endif
+			case AF_UNIX:
+				u = unix_sk(sk);
+				addr = smp_load_acquire(&u->addr);
+				if (!addr)
+					break;
+				if (u->path.dentry) {
+					audit_log_d_path(ab, " path=", &u->path);
+					break;
+				}
+				len = addr->len-sizeof(short);
+				p = &addr->name->sun_path[0];
+				audit_log_format(ab, " path=");
+				if (*p)
+					audit_log_untrustedstring(ab, p);
+				else
+					audit_log_n_hex(ab, p, len);
+				break;
+			}
+		}
+
+		switch (a->u.net->family) {
+		case AF_INET:
+			print_ipv4_addr(ab, a->u.net->v4info.saddr,
+					a->u.net->sport,
+					"saddr", "src");
+			print_ipv4_addr(ab, a->u.net->v4info.daddr,
+					a->u.net->dport,
+					"daddr", "dest");
+			break;
+		case AF_INET6:
+			print_ipv6_addr(ab, &a->u.net->v6info.saddr,
+					a->u.net->sport,
+					"saddr", "src");
+			print_ipv6_addr(ab, &a->u.net->v6info.daddr,
+					a->u.net->dport,
+					"daddr", "dest");
+			break;
+		}
+		if (a->u.net->netif > 0) {
+			struct net_device *dev;
+
+			/* NOTE: we always use init's namespace */
+			dev = dev_get_by_index(&init_net, a->u.net->netif);
+			if (dev) {
+				audit_log_format(ab, " netif=%s", dev->name);
+				dev_put(dev);
+			}
+		}
+		break;
+#ifdef CONFIG_KEYS
+	case LSM_AUDIT_DATA_KEY:
+		audit_log_format(ab, " key_serial=%u", a->u.key_struct.key);
+		if (a->u.key_struct.key_desc) {
+			audit_log_format(ab, " key_desc=");
+			audit_log_untrustedstring(ab, a->u.key_struct.key_desc);
+		}
+		break;
+#endif
+	case LSM_AUDIT_DATA_KMOD:
+		audit_log_format(ab, " kmod=");
+		audit_log_untrustedstring(ab, a->u.kmod_name);
+		break;
+	case LSM_AUDIT_DATA_IBPKEY: {
+		struct in6_addr sbn_pfx;
+
+		memset(&sbn_pfx.s6_addr, 0,
+		       sizeof(sbn_pfx.s6_addr));
+		memcpy(&sbn_pfx.s6_addr, &a->u.ibpkey->subnet_prefix,
+		       sizeof(a->u.ibpkey->subnet_prefix));
+		audit_log_format(ab, " pkey=0x%x subnet_prefix=%pI6c",
+				 a->u.ibpkey->pkey, &sbn_pfx);
+		break;
+	}
+	case LSM_AUDIT_DATA_IBENDPORT:
+		audit_log_format(ab, " device=%s port_num=%u",
+				 a->u.ibendport->dev_name,
+				 a->u.ibendport->port);
+		break;
+	case LSM_AUDIT_DATA_LOCKDOWN:
+		audit_log_format(ab, " lockdown_reason=\"%s\"",
+				 lockdown_reasons[a->u.reason]);
+		break;
+	case LSM_AUDIT_DATA_ANONINODE:
+		audit_log_format(ab, " anonclass=%s", a->u.anonclass);
+		break;
+	case LSM_AUDIT_DATA_NLMSGTYPE:
+		audit_log_format(ab, " nl-msgtype=%hu", a->u.nlmsg_type);
+		break;
+	} /* switch (a->type) */
+}
+
+/**
+ * dump_common_audit_data - helper to dump common audit data
+ * @ab : the audit buffer
+ * @a : common audit data
+ */
+static void dump_common_audit_data(struct audit_buffer *ab,
+				   const struct common_audit_data *a)
+{
+	char comm[sizeof(current->comm)];
+
+	audit_log_format(ab, " pid=%d comm=", task_tgid_nr(current));
+	audit_log_untrustedstring(ab, get_task_comm(comm, current));
+	audit_log_lsm_data(ab, a);
+}
+
+/**
+ * common_lsm_audit - generic LSM auditing function
+ * @a:  auxiliary audit data
+ * @pre_audit: lsm-specific pre-audit callback
+ * @post_audit: lsm-specific post-audit callback
+ *
+ * setup the audit buffer for common security information
+ * uses callback to print LSM specific information
+ */
+void common_lsm_audit(struct common_audit_data *a,
+	void (*pre_audit)(struct audit_buffer *, void *),
+	void (*post_audit)(struct audit_buffer *, void *))
+{
+	struct audit_buffer *ab;
+
+	if (a == NULL)
+		return;
+	/* we use GFP_ATOMIC so we won't sleep */
+	ab = audit_log_start(audit_context(), GFP_ATOMIC | __GFP_NOWARN,
+			     AUDIT_AVC);
+
+	if (ab == NULL)
+		return;
+
+	if (pre_audit)
+		pre_audit(ab, a);
+
+	dump_common_audit_data(ab, a);
+
+	if (post_audit)
+		post_audit(ab, a);
+
+	audit_log_end(ab);
+}