On Tue, Mar 16, 2021 at 12:26:05PM -0700, Linus Torvalds wrote:
> Note that the above very intentionally does allow the "we can go over
> the limit" case for another reason: we still have that regular
> *unconditional* get_page(), that has a "I absolutely need a temporary
> ref to this page, but I
On Tue, Mar 16, 2021 at 11:49 AM Kees Cook wrote:
>
> Right -- I saw that when digging through the thread. I'm honestly
> curious, though, why did the 0-day bot find a boot crash? (I can't
> imagine ucounts wrapped in 0.4 seconds.) So it looked like an
> increment-from-zero case, which seems like
On Mon, Mar 15, 2021 at 03:19:17PM -0700, Linus Torvalds wrote:
> It just saturates, and doesn't have the "don't do this" case, which
> the ucounts case *DOES* have.
Right -- I saw that when digging through the thread. I'm honestly
curious, though, why did the 0-day bot find a boot crash? (I can't
On Mon, Mar 15, 2021 at 3:03 PM Kees Cook wrote:
>
> On Wed, Mar 10, 2021 at 01:01:28PM +0100, Alexey Gladkov wrote:
> > The current implementation of the ucounts reference counter requires the
> > use of spin_lock. We're going to use get_ucounts() in more performance
> > critical areas like a han
On Wed, Mar 10, 2021 at 01:01:28PM +0100, Alexey Gladkov wrote:
> The current implementation of the ucounts reference counter requires the
> use of spin_lock. We're going to use get_ucounts() in more performance
> critical areas like a handling of RLIMIT_SIGPENDING.
This really looks like it shoul
On Wed, Mar 10, 2021 at 4:01 AM Alexey Gladkov wrote:
>
>
> +/* 127: arbitrary random number, small enough to assemble well */
> +#define refcount_zero_or_close_to_overflow(ucounts) \
> + ((unsigned int) atomic_read(&ucounts->count) + 127u <= 127u)
> +
> +struct ucounts *get_ucounts(struct u
The current implementation of the ucounts reference counter requires the
use of spin_lock. We're going to use get_ucounts() in more performance
critical areas like a handling of RLIMIT_SIGPENDING.
Now we need to use spin_lock only if we want to change the hashtable.
Signed-off-by: Alexey Gladkov
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