The patch titled
/proc/*/oom_score oops re badness
has been added to the -mm tree. Its filename is
proc-oom_score-oops-re-badness.patch
*** Remember to use Documentation/SubmitChecklist when testing your code ***
See http://www.zip.com.au/~akpm/linux/patches/stuff/added-to-mm.txt to find
out what to do about this
------------------------------------------------------
Subject: /proc/*/oom_score oops re badness
From: Alexey Dobriyan <adobriyan@xxxxx>
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@xxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
fs/proc/base.c | 2 ++
1 file changed, 2 insertions(+)
diff -puN fs/proc/base.c~proc-oom_score-oops-re-badness fs/proc/base.c
--- a/fs/proc/base.c~proc-oom_score-oops-re-badness
+++ a/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);
}
_
Patches currently in -mm which might be from adobriyan@xxxxx are
fix-race-between-proc_readdir-and-remove_proc_entry.patch
proc-remove-pathetic-deleted-warn_on.patch
race-between-cat-proc-kallsyms-and-rmmod.patch
fix-rmmod-read-write-races-in-proc-entries.patch
proc-oom_score-oops-re-badness.patch
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