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authorOleg Nesterov <oleg@redhat.com>2018-01-04 16:17:49 -0800
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>2018-01-10 09:27:08 +0100
commit83875f5825968bcab2dfd9f4531f1eb7e7eef05f (patch)
tree70088e3ad22e9cc3e57faa170c53961319a5452b
parentb17b901f0fea8e4b39711841d095f50d41bb081e (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.c2
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 */