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/proc/*/oom_score oops re badness

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Eternal quest to make

	while true; do cat /proc/fs/xfs/stat >/dev/null 2>/dev/null; done
	while true; do find /proc -type f 2>/dev/null | xargs cat >/dev/null 2>/dev/null; done
	while true; do modprobe xfs; rmmod xfs; done

work reliably continues and now kernel oopses in the following way:

BUG: unable to handle ... at virtual address 6b6b6b6b
EIP is at badness
process: cat
	proc_oom_score
	proc_info_read
	sys_fstat64
	vfs_read
	proc_info_read
	sys_read

Failing code is prefetch hidden in list_for_each_entry() in badness().
badness() is reachable from two points. One is proc_oom_score, another
is out_of_memory() => select_bad_process() => badness().

Second path grabs tasklist_lock, while first doesn't.

Signed-off-by: Alexey Dobriyan <adobriyan@sw.ru>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Alexey Dobriyan 2007-05-08 00:26:46 -07:00 committed by Linus Torvalds
parent 72c1bbf308
commit 19c5d45a09
1 changed files with 2 additions and 0 deletions
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2
fs/proc/base.c
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@ -314,7 +314,9 @@ static int proc_oom_score(struct task_struct *task, char *buffer)
struct timespec uptime;
do_posix_clock_monotonic_gettime(&uptime);
read_lock(&tasklist_lock);
points = badness(task, uptime.tv_sec);
read_unlock(&tasklist_lock);
return sprintf(buffer, "%lu\n", points);
}