From: Paul Moore paul@paul-moore.com
maillist inclusion category: bugfix bugzilla: 185906 https://gitee.com/openeuler/kernel/issues/I4N958?from=project-issue CVE: NA
Reference: https://patchwork.kernel.org/project/linux-audit/patch/163949858723.23091.53...
-------------------------------------------------------------------
Due to the audit control mutex necessary for serializing audit userspace messages we haven't been able to block/penalize userspace processes that attempt to send audit records while the system is under audit pressure. The result is that privileged userspace applications have a priority boost with respect to audit as they are not bound by the same audit queue throttling as the other tasks on the system.
This patch attempts to restore some balance to the system when under audit pressure by blocking these privileged userspace tasks after they have finished their audit processing, and dropped the audit control mutex, but before they return to userspace.
Reported-by: Gaosheng Cui cuigaosheng1@huawei.com Tested-by: Gaosheng Cui cuigaosheng1@huawei.com Reviewed-by: Richard Guy Briggs rgb@redhat.com Signed-off-by: Paul Moore paul@paul-moore.com Signed-off-by: Cui GaoSheng cuigaosheng1@huawei.com Reviewed-by: Xiu Jianfeng xiujianfeng@huawei.com Signed-off-by: Zheng Zengkai zhengzengkai@huawei.com --- kernel/audit.c | 18 +++++++++++++++++- 1 file changed, 17 insertions(+), 1 deletion(-)
diff --git a/kernel/audit.c b/kernel/audit.c index d784000921da..2a38cbaf3ddb 100644 --- a/kernel/audit.c +++ b/kernel/audit.c @@ -1540,6 +1540,20 @@ static void audit_receive(struct sk_buff *skb) nlh = nlmsg_next(nlh, &len); } audit_ctl_unlock(); + + /* can't block with the ctrl lock, so penalize the sender now */ + if (audit_backlog_limit && + (skb_queue_len(&audit_queue) > audit_backlog_limit)) { + DECLARE_WAITQUEUE(wait, current); + + /* wake kauditd to try and flush the queue */ + wake_up_interruptible(&kauditd_wait); + + add_wait_queue_exclusive(&audit_backlog_wait, &wait); + set_current_state(TASK_UNINTERRUPTIBLE); + schedule_timeout(audit_backlog_wait_time); + remove_wait_queue(&audit_backlog_wait, &wait); + } }
/* Log information about who is connecting to the audit multicast socket */ @@ -1824,7 +1838,9 @@ struct audit_buffer *audit_log_start(struct audit_context *ctx, gfp_t gfp_mask, * task_tgid_vnr() since auditd_pid is set in audit_receive_msg() * using a PID anchored in the caller's namespace * 2. generator holding the audit_cmd_mutex - we don't want to block - * while holding the mutex */ + * while holding the mutex, although we do penalize the sender + * later in audit_receive() when it is safe to block + */ if (!(auditd_test_task(current) || audit_ctl_owner_current())) { long stime = audit_backlog_wait_time;