Merge tag 'lsm-pr-20220829' of git://git.kernel.org/pub/scm/linux/kernel/git/pcmoore/lsm

Pull LSM support for IORING_OP_URING_CMD from Paul Moore:
 "Add SELinux and Smack controls to the io_uring IORING_OP_URING_CMD.

  These are necessary as without them the IORING_OP_URING_CMD remains
  outside the purview of the LSMs (Luis' LSM patch, Casey's Smack patch,
  and my SELinux patch). They have been discussed at length with the
  io_uring folks, and Jens has given his thumbs-up on the relevant
  patches (see the commit descriptions).

  There is one patch that is not strictly necessary, but it makes
  testing much easier and is very trivial: the /dev/null
  IORING_OP_URING_CMD patch."

* tag 'lsm-pr-20220829' of git://git.kernel.org/pub/scm/linux/kernel/git/pcmoore/lsm:
  Smack: Provide read control for io_uring_cmd
  /dev/null: add IORING_OP_URING_CMD support
  selinux: implement the security_uring_cmd() LSM hook
  lsm,io_uring: add LSM hooks for the new uring_cmd file op

Author: torvalds

drivers/char/mem.c

@@ -480,6 +480,11 @@ static ssize_t splice_write_null(struct pipe_inode_info *pipe, struct file *out,
 	return splice_from_pipe(pipe, out, ppos, len, flags, pipe_to_null);
 }
 
+static int uring_cmd_null(struct io_uring_cmd *ioucmd, unsigned int issue_flags)
+{
+	return 0;
+}
+
 static ssize_t read_iter_zero(struct kiocb *iocb, struct iov_iter *iter)
 {
 	size_t written = 0;
@@ -663,6 +668,7 @@ static const struct file_operations null_fops = {
 	.read_iter	= read_iter_null,
 	.write_iter	= write_iter_null,
 	.splice_write	= splice_write_null,
+	.uring_cmd	= uring_cmd_null,
 };
 
 static const struct file_operations __maybe_unused port_fops = {

include/linux/lsm_hook_defs.h

@@ -407,4 +407,5 @@ LSM_HOOK(int, 0, perf_event_write, struct perf_event *event)
 #ifdef CONFIG_IO_URING
 LSM_HOOK(int, 0, uring_override_creds, const struct cred *new)
 LSM_HOOK(int, 0, uring_sqpoll, void)
+LSM_HOOK(int, 0, uring_cmd, struct io_uring_cmd *ioucmd)
 #endif /* CONFIG_IO_URING */

include/linux/lsm_hooks.h

@@ -1582,6 +1582,9 @@
  *      Check whether the current task is allowed to spawn a io_uring polling
  *      thread (IORING_SETUP_SQPOLL).
  *
+ * @uring_cmd:
+ *      Check whether the file_operations uring_cmd is allowed to run.
+ *
  */
 union security_list_options {
 	#define LSM_HOOK(RET, DEFAULT, NAME, ...) RET (*NAME)(__VA_ARGS__);

include/linux/security.h

@@ -2060,6 +2060,7 @@ static inline int security_perf_event_write(struct perf_event *event)
 #ifdef CONFIG_SECURITY
 extern int security_uring_override_creds(const struct cred *new);
 extern int security_uring_sqpoll(void);
+extern int security_uring_cmd(struct io_uring_cmd *ioucmd);
 #else
 static inline int security_uring_override_creds(const struct cred *new)
 {
@@ -2069,6 +2070,10 @@ static inline int security_uring_sqpoll(void)
 {
 	return 0;
 }
+static inline int security_uring_cmd(struct io_uring_cmd *ioucmd)
+{
+	return 0;
+}
 #endif /* CONFIG_SECURITY */
 #endif /* CONFIG_IO_URING */
 

io_uring/uring_cmd.c

@@ -3,6 +3,7 @@
 #include <linux/errno.h>
 #include <linux/file.h>
 #include <linux/io_uring.h>
+#include <linux/security.h>
 
 #include <uapi/linux/io_uring.h>
 
@@ -88,6 +89,10 @@ int io_uring_cmd(struct io_kiocb *req, unsigned int issue_flags)
 	if (!req->file->f_op->uring_cmd)
 		return -EOPNOTSUPP;
 
+	ret = security_uring_cmd(ioucmd);
+	if (ret)
+		return ret;
+
 	if (ctx->flags & IORING_SETUP_SQE128)
 		issue_flags |= IO_URING_F_SQE128;
 	if (ctx->flags & IORING_SETUP_CQE32)

security/security.c

@@ -2660,4 +2660,8 @@ int security_uring_sqpoll(void)
 {
 	return call_int_hook(uring_sqpoll, 0);
 }
+int security_uring_cmd(struct io_uring_cmd *ioucmd)
+{
+	return call_int_hook(uring_cmd, 0, ioucmd);
+}
 #endif /* CONFIG_IO_URING */

security/selinux/hooks.c

@@ -91,6 +91,7 @@
 #include <uapi/linux/mount.h>
 #include <linux/fsnotify.h>
 #include <linux/fanotify.h>
+#include <linux/io_uring.h>
 
 #include "avc.h"
 #include "objsec.h"
@@ -6987,6 +6988,28 @@ static int selinux_uring_sqpoll(void)
 	return avc_has_perm(&selinux_state, sid, sid,
 			    SECCLASS_IO_URING, IO_URING__SQPOLL, NULL);
 }
+
+/**
+ * selinux_uring_cmd - check if IORING_OP_URING_CMD is allowed
+ * @ioucmd: the io_uring command structure
+ *
+ * Check to see if the current domain is allowed to execute an
+ * IORING_OP_URING_CMD against the device/file specified in @ioucmd.
+ *
+ */
+static int selinux_uring_cmd(struct io_uring_cmd *ioucmd)
+{
+	struct file *file = ioucmd->file;
+	struct inode *inode = file_inode(file);
+	struct inode_security_struct *isec = selinux_inode(inode);
+	struct common_audit_data ad;
+
+	ad.type = LSM_AUDIT_DATA_FILE;
+	ad.u.file = file;
+
+	return avc_has_perm(&selinux_state, current_sid(), isec->sid,
+			    SECCLASS_IO_URING, IO_URING__CMD, &ad);
+}
 #endif /* CONFIG_IO_URING */
 
 /*
@@ -7231,6 +7254,7 @@ static struct security_hook_list selinux_hooks[] __lsm_ro_after_init = {
 #ifdef CONFIG_IO_URING
 	LSM_HOOK_INIT(uring_override_creds, selinux_uring_override_creds),
 	LSM_HOOK_INIT(uring_sqpoll, selinux_uring_sqpoll),
+	LSM_HOOK_INIT(uring_cmd, selinux_uring_cmd),
 #endif
 
 	/*

security/selinux/include/classmap.h

@@ -253,7 +253,7 @@ const struct security_class_mapping secclass_map[] = {
 	{ "anon_inode",
 	  { COMMON_FILE_PERMS, NULL } },
 	{ "io_uring",
-	  { "override_creds", "sqpoll", NULL } },
+	  { "override_creds", "sqpoll", "cmd", NULL } },
 	{ NULL }
   };
 

security/smack/smack_lsm.c

@@ -42,6 +42,7 @@
 #include <linux/fs_context.h>
 #include <linux/fs_parser.h>
 #include <linux/watch_queue.h>
+#include <linux/io_uring.h>
 #include "smack.h"
 
 #define TRANS_TRUE	"TRUE"
@@ -4732,6 +4733,36 @@ static int smack_uring_sqpoll(void)
 	return -EPERM;
 }
 
+/**
+ * smack_uring_cmd - check on file operations for io_uring
+ * @ioucmd: the command in question
+ *
+ * Make a best guess about whether a io_uring "command" should
+ * be allowed. Use the same logic used for determining if the
+ * file could be opened for read in the absence of better criteria.
+ */
+static int smack_uring_cmd(struct io_uring_cmd *ioucmd)
+{
+	struct file *file = ioucmd->file;
+	struct smk_audit_info ad;
+	struct task_smack *tsp;
+	struct inode *inode;
+	int rc;
+
+	if (!file)
+		return -EINVAL;
+
+	tsp = smack_cred(file->f_cred);
+	inode = file_inode(file);
+
+	smk_ad_init(&ad, __func__, LSM_AUDIT_DATA_PATH);
+	smk_ad_setfield_u_fs_path(&ad, file->f_path);
+	rc = smk_tskacc(tsp, smk_of_inode(inode), MAY_READ, &ad);
+	rc = smk_bu_credfile(file->f_cred, file, MAY_READ, rc);
+
+	return rc;
+}
+
 #endif /* CONFIG_IO_URING */
 
 struct lsm_blob_sizes smack_blob_sizes __lsm_ro_after_init = {
@@ -4889,6 +4920,7 @@ static struct security_hook_list smack_hooks[] __lsm_ro_after_init = {
 #ifdef CONFIG_IO_URING
 	LSM_HOOK_INIT(uring_override_creds, smack_uring_override_creds),
 	LSM_HOOK_INIT(uring_sqpoll, smack_uring_sqpoll),
+	LSM_HOOK_INIT(uring_cmd, smack_uring_cmd),
 #endif
 };