Messages in this thread | | | Subject | Re: [PATCH v2 04/11] drivers/base/devcoredump: convert devcd_count to counter_atomic32 | From | Shuah Khan <> | Date | Wed, 7 Oct 2020 13:33:43 -0600 |
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On 10/7/20 12:15 PM, Kees Cook wrote: > On Tue, Oct 06, 2020 at 02:44:35PM -0600, Shuah Khan wrote: >> counter_atomic* is introduced to be used when a variable is used as >> a simple counter and doesn't guard object lifetimes. This clearly >> differentiates atomic_t usages that guard object lifetimes. >> >> counter_atomic* variables will wrap around to 0 when it overflows and >> should not be used to guard resource lifetimes, device usage and >> open counts that control state changes, and pm states. >> >> devcd_count is used to track dev_coredumpm device count and used in >> device name string. It doesn't guard object lifetimes, device usage >> counts, device open counts, and pm states. There is very little chance >> of this counter overflowing. Convert it to use counter_atomic32. >> >> This conversion doesn't change the overflow wrap around behavior. >> >> Reviewed-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> >> Signed-off-by: Shuah Khan <skhan@linuxfoundation.org> > > I actually wonder if this should use refcount_t just because it is > designed to be an alway-unique value. It is hard to imagine ever causing > this to overflow, but why not let it be protected? >
This is one of the cases where devcd_count doesn't guard lifetimes, however if it ever overflows, refcount_t is a better choice.
If we decide refcount_t is a better choice, I can drop this patch and send refcount_t conversion patch instead.
Greg! Any thoughts on refcount_t for this being a better choice?
thanks, -- Shuah
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