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authorVasily Averin <vvs@virtuozzo.com>2019-05-14 15:42:28 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2019-05-14 19:52:49 -0700
commit831246570d34692e0550da952d0655bdcc985419 (patch)
tree74ad4a7f33497497762446634c993b94a6ceed29 /kernel
parent9012d011660ea5cf2a623e1de207a2bc0ca6936d (diff)
downloadlinux-831246570d34692e0550da952d0655bdcc985419.tar.bz2
kernel/notifier.c: double register detection
By design notifiers can be registerd once only, 2nd register attempt called by mistake silently corrupts notifiers list. A few years ago I investigated described problem, the host was power cycled because of notifier list corruption. I've prepared this patch and applied it to the OpenVZ kernel and sent this patch but nobody commented on it. Later it helped us to detect a similar problem in the OpenVz kernel. Mistakes with notifier registration can happen for example during subsystem initialization from different namespaces, or because of a lost unregister in the roll-back path on initialization failures. The proposed check cannot prevent the described problem, however it allows us to detect its reason quickly without coredump analysis. Link: http://lkml.kernel.org/r/04127e71-4782-9bbb-fe5a-7c01e93a99b0@virtuozzo.com Signed-off-by: Vasily Averin <vvs@virtuozzo.com> Reviewed-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'kernel')
-rw-r--r--kernel/notifier.c1
1 files changed, 1 insertions, 0 deletions
diff --git a/kernel/notifier.c b/kernel/notifier.c
index 6196af8a8223..bfc95b3e4235 100644
--- a/kernel/notifier.c
+++ b/kernel/notifier.c
@@ -22,6 +22,7 @@ static int notifier_chain_register(struct notifier_block **nl,
struct notifier_block *n)
{
while ((*nl) != NULL) {
+ WARN_ONCE(((*nl) == n), "double register detected");
if (n->priority > (*nl)->priority)
break;
nl = &((*nl)->next);