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closures: CLOSURE_CALLBACK() to fix type punning

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Control flow integrity is now checking that type signatures match on
indirect function calls. That breaks closures, which embed a work_struct
in a closure in such a way that a closure_fn may also be used as a
workqueue fn by the underlying closure code.

So we have to change closure fns to take a work_struct as their
argument - but that results in a loss of clarity, as closure fns have
different semantics from normal workqueue functions (they run owning a
ref on the closure, which must be released with continue_at() or
closure_return()).

Thus, this patc introduces CLOSURE_CALLBACK() and closure_type() macros
as suggested by Kees, to smooth things over a bit.

Suggested-by: Kees Cook <keescook@chromium.org>
Cc: Coly Li <colyli@suse.de>
Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>
This commit is contained in:
Kent Overstreet
2023-11-17 19:13:27 -05:00
parent 98b1cc82c4
commit d4e3b928ab
16 changed files with 127 additions and 124 deletions
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5
lib/closure.c
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@@ -36,7 +36,7 @@ static inline void closure_put_after_sub(struct closure *cl, int flags)
closure_debug_destroy(cl);
if (destructor)
destructor(cl);
destructor(&cl->work);
if (parent)
closure_put(parent);
@@ -108,8 +108,9 @@ struct closure_syncer {
int done;
};
static void closure_sync_fn(struct closure *cl)
static CLOSURE_CALLBACK(closure_sync_fn)
{
struct closure *cl = container_of(ws, struct closure, work);
struct closure_syncer *s = cl->s;
struct task_struct *p;