On 6/29/2023 7:14 PM, Paul Moore wrote:

On Jun 29, 2023 Casey Schaufler [off-list ref] wrote:

quoted

Add lsm_name_to_attr(), which translates a text string to a
LSM_ATTR value if one is available.

Add lsm_fill_user_ctx(), which fills a struct lsm_ctx, including
the trailing attribute value.

All are used in module specific components of LSM system calls.

Signed-off-by: Casey Schaufler <casey@schaufler-ca.com>
Reviewed-by: Serge Hallyn <serge@hallyn.com>
---
 include/linux/security.h | 14 +++++++++++++
 security/lsm_syscalls.c  | 24 ++++++++++++++++++++++
 security/security.c      | 44 ++++++++++++++++++++++++++++++++++++++++
 3 files changed, 82 insertions(+)

..

quoted

diff --git a/security/security.c b/security/security.c
index 199db23581f1..72ad7197b2c9 100644
--- a/security/security.c
+++ b/security/security.c

@@ -770,6 +770,50 @@ static int lsm_superblock_alloc(struct super_block *sb)
 	return 0;
 }
 
+/**
+ * lsm_fill_user_ctx - Fill a user space lsm_ctx structure
+ * @ctx: an LSM context to be filled
+ * @context: the new context value
+ * @context_size: the size of the new context value
+ * @id: LSM id
+ * @flags: LSM defined flags
+ *
+ * Fill all of the fields in a user space lsm_ctx structure.
+ * Caller is assumed to have verified that @ctx has enough space
+ * for @context.
+ *
+ * The total length is padded to a multiple of 64 bits to
+ * accomodate possible alignment issues.

We should drop the sentence above now that alignment is the caller's
responsibility, but since that was largely my fault I can fix this up
during the merge assuming you're okay with that Casey.

I have to fix the error in patch 8/11 anyway. I can fix this, too.

quoted

+ * Returns 0 on success, -EFAULT on a copyout error, -ENOMEM
+ * if memory can't be allocated.
+ */
+int lsm_fill_user_ctx(struct lsm_ctx __user *ctx, void *context,
+		      size_t context_size, u64 id, u64 flags)
+{
+	struct lsm_ctx *lctx;
+	size_t locallen = struct_size(lctx, ctx, context_size);
+	int rc = 0;
+
+	lctx = kzalloc(locallen, GFP_KERNEL);
+	if (lctx == NULL)
+		return -ENOMEM;
+
+	lctx->id = id;
+	lctx->flags = flags;
+	lctx->ctx_len = context_size;
+	lctx->len = locallen;
+
+	memcpy(lctx->ctx, context, context_size);
+
+	if (copy_to_user(ctx, lctx, locallen))
+		rc = -EFAULT;
+
+	kfree(lctx);
+
+	return rc;
+}
+
 /*
  * The default value of the LSM hook is defined in linux/lsm_hook_defs.h and
  * can be accessed with:
-- 
2.40.1

--
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