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authorVasiliy Kulikov <segoon@openwall.com>2011-06-27 16:18:11 -0700
committerGreg Kroah-Hartman <gregkh@suse.de>2011-07-13 05:29:25 +0200
commit68e62de3e747b9ae5e811a77ccece7c425dae830 (patch)
tree59b341aae5d639d42174b354bbfd8fde24cdfdb5 /drivers
parent06ce414d4a0811a979a82cddc3e429e6bd704c98 (diff)
downloadlinux-linaro-stable-68e62de3e747b9ae5e811a77ccece7c425dae830.tar.gz
taskstats: don't allow duplicate entries in listener mode
commit 26c4caea9d697043cc5a458b96411b86d7f6babd upstream. Currently a single process may register exit handlers unlimited times. It may lead to a bloated listeners chain and very slow process terminations. Eg after 10KK sent TASKSTATS_CMD_ATTR_REGISTER_CPUMASKs ~300 Mb of kernel memory is stolen for the handlers chain and "time id" shows 2-7 seconds instead of normal 0.003. It makes it possible to exhaust all kernel memory and to eat much of CPU time by triggerring numerous exits on a single CPU. The patch limits the number of times a single process may register itself on a single CPU to one. One little issue is kept unfixed - as taskstats_exit() is called before exit_files() in do_exit(), the orphaned listener entry (if it was not explicitly deregistered) is kept until the next someone's exit() and implicit deregistration in send_cpu_listeners(). So, if a process registered itself as a listener exits and the next spawned process gets the same pid, it would inherit taskstats attributes. Signed-off-by: Vasiliy Kulikov <segooon@gmail.com> Cc: Balbir Singh <bsingharora@gmail.com> 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@suse.de>
Diffstat (limited to 'drivers')
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