From: Elad Lahav <e2lahav@gmail.com>
To: perfbook@vger.kernel.org
Subject: Hazard pointers: suspicious dereference
Date: Sun, 13 Nov 2022 10:20:18 -0500 [thread overview]
Message-ID: <CAJbg=FWTVdoZr2uzDeSMcUE-0EGQbFgtVR6NvoRQ9Y+P1LSoRQ@mail.gmail.com> (raw)
hp_try_record() takes a pointer to a pointer, casts it to void **, and
then passes it to _h_t_r_impl(). So far so good.
hp_record() takes a pointer to a pointer, but dereferences it when
calling hp_try_record(). That seems odd to me. Let's say we have a
structure foo_t, and a pointer to it, foo_p. Then
hp_record((void **)&foo_p, hp) =>
hp_try_record(*p, hp) // p is pointer to pointer to foo_s =>
_h_t_r_impl((void **)p, hp) // p is a pointer to foo_s, cast as (void **) =>
tmp = READ_ONCE(*p) // reading from the first bytes of foo_s as an address
I also tried building the example route_hazard.c such that it uses
hp_record() instead of hp_try_record(), and it crashes as I expected.
Am I missing something?
--Elad
next reply other threads:[~2022-11-13 15:20 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-11-13 15:20 Elad Lahav [this message]
2022-11-20 18:23 ` Hazard pointers: suspicious dereference Elad Lahav
2022-11-20 23:40 ` Paul McKenney
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