Re: [PATCH v10 7/11] LSM: Helpers for attribute names and filling lsm_ctx
From: Paul Moore <paul@paul-moore.com>
Date: 2023-06-07 22:33:10
Also in:
linux-security-module, lkml, llvm, oe-kbuild-all
On Apr 28, 2023 kernel test robot [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. The .len value is padded to a multiple of 64 bits for alignment. All are used in module specific components of LSM system calls. Signed-off-by: Casey Schaufler <casey@schaufler-ca.com> --- include/linux/security.h | 13 ++++++++++++ security/lsm_syscalls.c | 24 ++++++++++++++++++++++ security/security.c | 44 ++++++++++++++++++++++++++++++++++++++++ 3 files changed, 81 insertions(+)
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quoted hunk ↗ jump to hunk
diff --git a/security/security.c b/security/security.c index 94b78bfd06b9..8c877d639cae 100644 --- a/security/security.c +++ b/security/security.c@@ -761,6 +761,50 @@ 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. + * + * 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 = ALIGN(struct_size(lctx, ctx, context_size), 8);
See my comment in 7/11 regarding the alignment calculation here.
+ 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: -- 2.39.2
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