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nvme: code command_id with a genctr for use-after-free validation
[ Upstream commit e7006de ] We cannot detect a (perhaps buggy) controller that is sending us a completion for a request that was already completed (for example sending a completion twice), this phenomenon was seen in the wild a few times. So to protect against this, we use the upper 4 msbits of the nvme sqe command_id to use as a 4-bit generation counter and verify it matches the existing request generation that is incrementing on every execution. The 16-bit command_id structure now is constructed by: | xxxx | xxxxxxxxxxxx | gen request tag This means that we are giving up some possible queue depth as 12 bits allow for a maximum queue depth of 4095 instead of 65536, however we never create such long queues anyways so no real harm done. Suggested-by: Keith Busch <kbusch@kernel.org> Signed-off-by: Sagi Grimberg <sagi@grimberg.me> Acked-by: Keith Busch <kbusch@kernel.org> Reviewed-by: Hannes Reinecke <hare@suse.de> Reviewed-by: Daniel Wagner <dwagner@suse.de> Tested-by: Daniel Wagner <dwagner@suse.de> Signed-off-by: Christoph Hellwig <hch@lst.de> Signed-off-by: Sasha Levin <sashal@kernel.org>
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