diff options
| author | Oleg Nesterov <oleg@redhat.com> | 2018-01-04 16:17:49 -0800 |
|---|---|---|
| committer | Ben Hutchings <ben@decadent.org.uk> | 2018-03-03 15:52:13 +0000 |
| commit | 275927ccd93bbc1b25d98221dedfc692d587442b (patch) | |
| tree | 0a69dd93f6f816977075369d4a04b8ea65d78224 | |
| parent | 631fcf6297b544ff8dbe8ff5f6b64993b7e0c6f9 (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>
[bwh: Backported to 3.16: adjust context]
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
| -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 808a86ff229d..591bdcd20e8f 100644 --- a/kernel/acct.c +++ b/kernel/acct.c @@ -107,7 +107,7 @@ static int check_free_space(struct bsd_acct_struct *acct, struct file *file) spin_lock(&acct_lock); res = acct->active; - if (!file || time_is_before_jiffies(acct->needcheck)) + if (!file || time_is_after_jiffies(acct->needcheck)) goto out; spin_unlock(&acct_lock); |