Messages in this thread Patch in this message | | | Date | Sun, 01 Jul 2012 18:20:17 +0100 | From | Ben Hutchings <> | Subject | [ 11/48] mm: correctly synchronize rss-counters at exit/exec |
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3.2-stable review patch. If anyone has any objections, please let me know.
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From: Konstantin Khlebnikov <khlebnikov@openvz.org>
commit 4fe7efdbdfb1c7e7a7f31decfd831c0f31d37091 upstream.
do_exit() and exec_mmap() call sync_mm_rss() before mm_release() does put_user(clear_child_tid) which can update task->rss_stat and thus make mm->rss_stat inconsistent. This triggers the "BUG:" printk in check_mm().
Let's fix this bug in the safest way, and optimize/cleanup this later.
Reported-by: Markus Trippelsdorf <markus@trippelsdorf.de> Signed-off-by: Konstantin Khlebnikov <khlebnikov@openvz.org> Cc: Oleg Nesterov <oleg@redhat.com> Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com> Cc: Hugh Dickins <hughd@google.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org> [bwh: Backported to 3.2: sync_mm_rss() still takes a struct task_struct *] Signed-off-by: Ben Hutchings <ben@decadent.org.uk> --- --- a/fs/exec.c +++ b/fs/exec.c @@ -820,10 +820,10 @@ /* Notify parent that we're no longer interested in the old VM */ tsk = current; old_mm = current->mm; - sync_mm_rss(tsk, old_mm); mm_release(tsk, old_mm); if (old_mm) { + sync_mm_rss(tsk, old_mm); /* * Make sure that if there is a core dump in progress * for the old mm, we get out and die instead of going --- a/kernel/exit.c +++ b/kernel/exit.c @@ -641,6 +641,7 @@ mm_release(tsk, mm); if (!mm) return; + sync_mm_rss(tsk, mm); /* * Serialize with any possible pending coredump. * We must hold mmap_sem around checking core_state
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