From: Paul Moore paul@paul-moore.com
commit a3727a8bac0a9e77c70820655fd8715523ba3db7 upstream.
Jann Horn reported a problem with commit eb1231f73c4d ("selinux: clarify task subjective and objective credentials") where some LSM hooks were attempting to access the subjective credentials of a task other than the current task. Generally speaking, it is not safe to access another task's subjective credentials and doing so can cause a number of problems.
Further, while looking into the problem, I realized that Smack was suffering from a similar problem brought about by a similar commit 1fb057dcde11 ("smack: differentiate between subjective and objective task credentials").
This patch addresses this problem by restoring the use of the task's objective credentials in those cases where the task is other than the current executing task. Not only does this resolve the problem reported by Jann, it is arguably the correct thing to do in these cases.
Cc: stable@vger.kernel.org Fixes: eb1231f73c4d ("selinux: clarify task subjective and objective credentials") Fixes: 1fb057dcde11 ("smack: differentiate between subjective and objective task credentials") Reported-by: Jann Horn jannh@google.com Acked-by: Eric W. Biederman ebiederm@xmission.com Acked-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/selinux/hooks.c | 4 ++-- security/smack/smack_lsm.c | 4 ++-- 2 files changed, 4 insertions(+), 4 deletions(-)
--- a/security/selinux/hooks.c +++ b/security/selinux/hooks.c @@ -2155,7 +2155,7 @@ static int selinux_ptrace_access_check(s static int selinux_ptrace_traceme(struct task_struct *parent) { return avc_has_perm(&selinux_state, - task_sid_subj(parent), task_sid_obj(current), + task_sid_obj(parent), task_sid_obj(current), SECCLASS_PROCESS, PROCESS__PTRACE, NULL); }
@@ -6218,7 +6218,7 @@ static int selinux_msg_queue_msgrcv(stru struct ipc_security_struct *isec; struct msg_security_struct *msec; struct common_audit_data ad; - u32 sid = task_sid_subj(target); + u32 sid = task_sid_obj(target); int rc;
isec = selinux_ipc(msq); --- a/security/smack/smack_lsm.c +++ b/security/smack/smack_lsm.c @@ -2016,7 +2016,7 @@ static int smk_curacc_on_task(struct tas const char *caller) { struct smk_audit_info ad; - struct smack_known *skp = smk_of_task_struct_subj(p); + struct smack_known *skp = smk_of_task_struct_obj(p); int rc;
smk_ad_init(&ad, caller, LSM_AUDIT_DATA_TASK); @@ -3480,7 +3480,7 @@ static void smack_d_instantiate(struct d */ static int smack_getprocattr(struct task_struct *p, char *name, char **value) { - struct smack_known *skp = smk_of_task_struct_subj(p); + struct smack_known *skp = smk_of_task_struct_obj(p); char *cp; int slen;