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[1] 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.
[1] 2.6.21-rc3-something + patches for all proc races I've already
posted + patch for proxying proc directories similar to proxying
proc regular files.
Signed-off-by: Alexey Dobriyan <[EMAIL PROTECTED]>
---
fs/proc/base.c | 2 ++
1 file changed, 2 insertions(+)
--- a/fs/proc/base.c
+++ b/fs/proc/base.c
@@ -310,7 +310,9 @@ static int proc_oom_score(struct task_st
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);
}
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