Re: NULL dereference OOPS on SysRq-w
From: Dan Noe
Date: Mon Apr 28 2008 - 03:02:28 EST
Dave Young wrote:
[snip]
I have a fix for the NULL pointer reference BUG, tested on my pc.
---
"m" will be NULL if seq_printf & seq_puts is called from sched_debug_show
Use SEQ_* macros to fix it
Signed-off-by: Dave Young <hidave.darkstar@xxxxxxxxx>
There is actually already a patch out for this which simply hasn't made
it upstream yet - Mike Galbraith emailed me with it and it indeed fixes
the problem. I hadn't realized his email didn't go to lkml.. otherwise
I would have echoed that here to avoid wasting people's time. My apologies.
Cheers,
Dan
===
Here is his message:
From: efault@xxxxxx
Peter's fix didn't make it up-stream.
Subject: sched: fix oops
sched_debug uses SEQ_printf to use printk when the seqfile 'm' is NULL.
Instead of doing that here too; choose to not output the weight tree
to cut back on output.
Signed-off-by: Peter Zijlstra <a.p.zijlstra@xxxxxxxxx>
---
diff --git a/kernel/sched_fair.c b/kernel/sched_fair.c
index 89fa32b..353a481 100644
--- a/kernel/sched_fair.c
+++ b/kernel/sched_fair.c
@@ -1643,8 +1643,10 @@ static void print_cfs_stats(struct seq_file *m,
int cpu)
for_each_leaf_cfs_rq(cpu_rq(cpu), cfs_rq)
print_cfs_rq(m, cpu, cfs_rq);
- seq_printf(m, "\nWeight tree:\n");
- print_cfs_rq_tasks(m, &cpu_rq(cpu)->cfs, 1);
+ if (m) {
+ seq_printf(m, "\nWeight tree:\n");
+ print_cfs_rq_tasks(m, &cpu_rq(cpu)->cfs, 1);
+ }
rcu_read_unlock();
}
#endif
--
/--------------- - - - - - -
| Dan Noe
| http://isomerica.net/~dpn/
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