[PATCH 5.19 161/192] Smack: Provide read control for io_uring_cmd

Greg Kroah-Hartman
2022-09-13T14:30:57Z

From: Casey Schaufler <casey@schaufler-ca.com>

commit dd9373402280cf4715fdc8fd5070f7d039e43511 upstream.

Limit io_uring "cmd" options to files for which the caller has
Smack read access. There may be cases where the cmd option may
be closer to a write access than a read, but there is no way
to make that determination.

Cc: stable@vger.kernel.org
Fixes: ee692a21e9bf ("fs,io_uring: add infrastructure for uring-cmd")
Signed-off-by: Casey Schaufler <casey@schaufler-ca.com>
Signed-off-by: Paul Moore <paul@paul-moore.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
security/smack/smack_lsm.c | 32 ++++++++++++++++++++++++++++++++
1 file changed, 32 insertions(+)

--- a/security/smack/smack_lsm.c
+++ b/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"
@@ -4739,6 +4740,36 @@ 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 = {
@@ -4896,6 +4927,7 @@ static struct security_hook_list smack_h
#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
};