diff options
| author | Oleg Nesterov <oleg@redhat.com> | 2018-01-04 16:17:49 -0800 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2018-01-10 09:27:08 +0100 |
| commit | 83875f5825968bcab2dfd9f4531f1eb7e7eef05f (patch) | |
| tree | 70088e3ad22e9cc3e57faa170c53961319a5452b | |
| parent | b17b901f0fea8e4b39711841d095f50d41bb081e (diff) | |
kernel/acct.c: fix the acct->needcheck check in check_free_space()
commit 4d9570158b6260f449e317a5f9ed030c2504a615 upstream.
As Tsukada explains, the time_is_before_jiffies(acct->needcheck) check
is very wrong, we need time_is_after_jiffies() to make sys_acct() work.
Ignoring the overflows, the code should "goto out" if needcheck >
jiffies, while currently it checks "needcheck < jiffies" and thus in the
likely case check_free_space() does nothing until jiffies overflow.
In particular this means that sys_acct() is simply broken, acct_on()
sets acct->needcheck = jiffies and expects that check_free_space()
should set acct->active = 1 after the free-space check, but this won't
happen if jiffies increments in between.
This was broken by commit 32dc73086015 ("get rid of timer in
kern/acct.c") in 2011, then another (correct) commit 795a2f22a8ea
("acct() should honour the limits from the very beginning") made the
problem more visible.
Link: http://lkml.kernel.org/r/20171213133940.GA6554@redhat.com
Fixes: 32dc73086015 ("get rid of timer in kern/acct.c")
Reported-by: TSUKADA Koutaro <tsukada@ascade.co.jp>
Suggested-by: TSUKADA Koutaro <tsukada@ascade.co.jp>
Signed-off-by: Oleg Nesterov <oleg@redhat.com>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
| -rw-r--r-- | kernel/acct.c | 2 |
1 files changed, 1 insertions, 1 deletions
diff --git a/kernel/acct.c b/kernel/acct.c index 74963d192c5d..37f1dc696fbd 100644 --- a/kernel/acct.c +++ b/kernel/acct.c @@ -99,7 +99,7 @@ static int check_free_space(struct bsd_acct_struct *acct) { struct kstatfs sbuf; - if (time_is_before_jiffies(acct->needcheck)) + if (time_is_after_jiffies(acct->needcheck)) goto out; /* May block */ |