From: Kees Cook <keescook@chromium.org>
To: Casey Schaufler <casey@schaufler-ca.com>
Cc: casey.schaufler@intel.com, jmorris@namei.org,
linux-security-module@vger.kernel.org, selinux@vger.kernel.org,
john.johansen@canonical.com, penguin-kernel@i-love.sakura.ne.jp,
paul@paul-moore.com, sds@tycho.nsa.gov
Subject: Re: [PATCH 14/27] LSM: Specify which LSM to display
Date: Mon, 29 Jul 2019 10:05:00 -0700 [thread overview]
Message-ID: <201907290959.747536016E@keescook> (raw)
In-Reply-To: <20190726233923.2570-15-casey@schaufler-ca.com>
On Fri, Jul 26, 2019 at 04:39:10PM -0700, Casey Schaufler wrote:
> When a program is executed in a way that changes its privilege
> the display is reset to the initial state to prevent unprivileged
> programs from tricking it into setting an unexpected display.
> [...]
> diff --git a/security/security.c b/security/security.c
> index 8927508b2142..4dd4ebeda18d 100644
> --- a/security/security.c
> +++ b/security/security.c
> @@ -835,7 +857,18 @@ int security_vm_enough_memory_mm(struct mm_struct *mm, long pages)
>
> int security_bprm_set_creds(struct linux_binprm *bprm)
> {
> - return call_int_hook(bprm_set_creds, 0, bprm);
> + int *disp = current->security;
> + int rc;
> +
> + rc = call_int_hook(bprm_set_creds, 0, bprm);
> +
> + /*
> + * Reset the "display" LSM if privilege has been elevated.
> + */
> + if (bprm->cap_elevated && disp)
> + *disp = LSMBLOB_INVALID;
> +
> + return rc;
> }
I think this is the wrong place to check this. This is called in
prepare_binprm(), which is very early in the execve() process. By my
reading this will change the forked process's display first before the
exec happens (which may potentially fail) -- this needs to be changing
the final state once exec is under way (past the "point of no return" in
flush_old_exec()).
Also, the consolidation of privilege information happens into
bprm->secureexec in setup_new_exec(), so I think you want to test
secureexec not just cap_elevated.
So the test/clear should likely happen in finalize_exec() since it's a
runtime state, not a memory layout-changing state (which would need to
happen earlier).
--
Kees Cook
next prev parent reply other threads:[~2019-07-29 17:05 UTC|newest]
Thread overview: 35+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-07-26 23:38 [PATCH v5 00/27] LSM: Module stacking for AppArmor Casey Schaufler
2019-07-26 23:38 ` [PATCH 01/27] LSM: Infrastructure management of the sock security Casey Schaufler
2019-07-26 23:38 ` [PATCH 02/27] LSM: Infrastructure management of the key blob Casey Schaufler
2019-07-26 23:38 ` [PATCH 03/27] LSM: Create and manage the lsmblob data structure Casey Schaufler
2019-07-26 23:39 ` [PATCH 04/27] LSM: Use lsmblob in security_audit_rule_match Casey Schaufler
2019-07-26 23:39 ` [PATCH 05/27] LSM: Use lsmblob in security_kernel_act_as Casey Schaufler
2019-07-26 23:39 ` [PATCH 06/27] net: Prepare UDS for security module stacking Casey Schaufler
2019-07-26 23:39 ` [PATCH 07/27] LSM: Use lsmblob in security_secctx_to_secid Casey Schaufler
2019-07-26 23:39 ` [PATCH 08/27] LSM: Use lsmblob in security_secid_to_secctx Casey Schaufler
2019-07-26 23:39 ` [PATCH 09/27] LSM: Use lsmblob in security_ipc_getsecid Casey Schaufler
2019-07-26 23:39 ` [PATCH 10/27] LSM: Use lsmblob in security_task_getsecid Casey Schaufler
2019-07-26 23:39 ` [PATCH 11/27] LSM: Use lsmblob in security_inode_getsecid Casey Schaufler
2019-07-26 23:39 ` [PATCH 12/27] LSM: Use lsmblob in security_cred_getsecid Casey Schaufler
2019-07-26 23:39 ` [PATCH 13/27] IMA: Change internal interfaces to use lsmblobs Casey Schaufler
2019-07-26 23:39 ` [PATCH 14/27] LSM: Specify which LSM to display Casey Schaufler
2019-07-29 17:05 ` Kees Cook [this message]
2019-07-26 23:39 ` [PATCH 15/27] LSM: Ensure the correct LSM context releaser Casey Schaufler
2019-07-26 23:39 ` [PATCH 16/27] LSM: Use lsmcontext in security_secid_to_secctx Casey Schaufler
2019-07-26 23:39 ` [PATCH 17/27] LSM: Use lsmcontext in security_dentry_init_security Casey Schaufler
2019-07-26 23:39 ` [PATCH 18/27] LSM: Use lsmcontext in security_inode_getsecctx Casey Schaufler
2019-07-26 23:39 ` [PATCH 19/27] LSM: security_secid_to_secctx in netlink netfilter Casey Schaufler
2019-07-26 23:39 ` [PATCH 20/27] NET: Store LSM netlabel data in a lsmblob Casey Schaufler
2019-07-26 23:39 ` [PATCH 21/27] SELinux: Verify LSM display sanity in binder Casey Schaufler
2019-07-26 23:39 ` [PATCH 22/27] Audit: Add subj_LSM fields when necessary Casey Schaufler
2019-07-26 23:39 ` [PATCH 23/27] Audit: Include object data for all security modules Casey Schaufler
2019-07-26 23:39 ` [PATCH 24/27] LSM: Provide an user space interface for the default display Casey Schaufler
2019-07-29 17:15 ` Kees Cook
2019-07-26 23:39 ` [PATCH 25/27] NET: Add SO_PEERCONTEXT for multiple LSMs Casey Schaufler
2019-07-29 13:00 ` Simon McVittie
2019-07-29 15:04 ` Casey Schaufler
2019-07-26 23:39 ` [PATCH 26/27] LSM: Add /proc attr entry for full LSM context Casey Schaufler
2019-07-29 17:19 ` Kees Cook
2019-07-29 19:22 ` Casey Schaufler
2019-07-29 21:40 ` Kees Cook
2019-07-26 23:39 ` [PATCH 27/27] AppArmor: Remove the exclusive flag Casey Schaufler
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