From: Juri Lelli Date: Tue, 13 May 2014 12:11:31 +0000 (+0200) Subject: sched/deadline: Restrict user params max value to 2^63 ns X-Git-Tag: omap-for-v3.16/fixes-against-rc1~116^2~3 X-Git-Url: http://git.openpandora.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=b0827819b0da4acfbc1df1e05edcf50efd07cbd1;p=pandora-kernel.git sched/deadline: Restrict user params max value to 2^63 ns Michael Kerrisk noticed that creating SCHED_DEADLINE reservations with certain parameters (e.g, a runtime of something near 2^64 ns) can cause a system freeze for some amount of time. The problem is that in the interface we have u64 sched_runtime; while internally we need to have a signed runtime (to cope with budget overruns) s64 runtime; At the time we setup a new dl_entity we copy the first value in the second. The cast turns out with negative values when sched_runtime is too big, and this causes the scheduler to go crazy right from the start. Moreover, considering how we deal with deadlines wraparound (s64)(a - b) < 0 we also have to restrict acceptable values for sched_{deadline,period}. This patch fixes the thing checking that user parameters are always below 2^63 ns (still large enough for everyone). It also rewrites other conditions that we check, since in __checkparam_dl we don't have to deal with deadline wraparounds and what we have now erroneously fails when the difference between values is too big. Reported-by: Michael Kerrisk Suggested-by: Peter Zijlstra Signed-off-by: Juri Lelli Signed-off-by: Peter Zijlstra Cc: Cc: Dario Faggioli Cc: Dave Jones Cc: Linus Torvalds Link: http://lkml.kernel.org/r/20140513141131.20d944f81633ee937f256385@gmail.com Signed-off-by: Ingo Molnar --- Reading git-diff-tree failed