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Commit 82919919 authored by Andrew Morton's avatar Andrew Morton Committed by Linus Torvalds
Browse files

kernel/audit.c: avoid negative sleep durations 



audit_log_start() performs the same jiffies comparison in two places.
If sufficient time has elapsed between the two comparisons, the second
one produces a negative sleep duration:

  schedule_timeout: wrong timeout value fffffffffffffff0
  Pid: 6606, comm: trinity-child1 Not tainted 3.8.0-rc1+ #43
  Call Trace:
    schedule_timeout+0x305/0x340
    audit_log_start+0x311/0x470
    audit_log_exit+0x4b/0xfb0
    __audit_syscall_exit+0x25f/0x2c0
    sysret_audit+0x17/0x21

Fix it by performing the comparison a single time.

Reported-by: default avatarDave Jones <davej@redhat.com>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: Eric Paris <eparis@redhat.com>
Reviewed-by: default avatarKees Cook <keescook@chromium.org>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 0644ec0c

kernel/audit.c

+23 −13
Original line number Diff line number Diff line
@@ -1101,6 +1101,23 @@ static inline void audit_get_stamp(struct audit_context *ctx, 
	}

}



/*

 * Wait for auditd to drain the queue a little

 */

static void wait_for_auditd(unsigned long sleep_time)

{

	DECLARE_WAITQUEUE(wait, current);

	set_current_state(TASK_INTERRUPTIBLE);

	add_wait_queue(&audit_backlog_wait, &wait);



	if (audit_backlog_limit &&

	    skb_queue_len(&audit_skb_queue) > audit_backlog_limit)

		schedule_timeout(sleep_time);



	__set_current_state(TASK_RUNNING);

	remove_wait_queue(&audit_backlog_wait, &wait);

}



/* Obtain an audit buffer.  This routine does locking to obtain the

 * audit buffer, but then no locking is required for calls to

 * audit_log_*format.  If the tsk is a task that is currently in a
@@ -1146,20 +1163,13 @@ struct audit_buffer *audit_log_start(struct audit_context *ctx, gfp_t gfp_mask, 


	while (audit_backlog_limit

	       && skb_queue_len(&audit_skb_queue) > audit_backlog_limit + reserve) {

		if (gfp_mask & __GFP_WAIT && audit_backlog_wait_time

		    && time_before(jiffies, timeout_start + audit_backlog_wait_time)) {



			/* Wait for auditd to drain the queue a little */

			DECLARE_WAITQUEUE(wait, current);

			set_current_state(TASK_INTERRUPTIBLE);

			add_wait_queue(&audit_backlog_wait, &wait);

		if (gfp_mask & __GFP_WAIT && audit_backlog_wait_time) {

			unsigned long sleep_time;



			if (audit_backlog_limit &&

			    skb_queue_len(&audit_skb_queue) > audit_backlog_limit)

				schedule_timeout(timeout_start + audit_backlog_wait_time - jiffies);



			__set_current_state(TASK_RUNNING);

			remove_wait_queue(&audit_backlog_wait, &wait);

			sleep_time = timeout_start + audit_backlog_wait_time -

					jiffies;

			if ((long)sleep_time > 0)

				wait_for_auditd(sleep_time);

			continue;

		}

		if (audit_rate_check() && printk_ratelimit())