Re: [PATCH v12 7/11] LSM: Helpers for attribute names and filling lsm_ctx
From: Paul Moore <paul@paul-moore.com>
Date: 2023-06-30 02:15:15
Also in:
linux-security-module, lkml
On Jun 29, 2023 Casey Schaufler [off-list ref] wrote:
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 hunk ↗ jump to hunk
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.
+ * 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:
--
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