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Oleg Nesterov authored
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 32dc7308 ("get rid of timer in kern/acct.c") in 2011, then another (correct) commit 795a2f22 ("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: 32dc7308 ("get rid of timer in kern/acct.c") Reported-by: ...
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