Commit Graph

5 Commits

Author SHA1 Message Date
Kent Overstreet
d4e3b928ab closures: CLOSURE_CALLBACK() to fix type punning
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>
2023-11-24 00:29:58 -05:00
Kent Overstreet
ee526b88ca closures: Fix race in closure_sync()
As pointed out by Linus, closure_sync() was racy; we could skip blocking
immediately after a get() and a put(), but then that would skip any
barrier corresponding to the other thread's put() barrier.

To fix this, always do the full __closure_sync() sequence whenever any
get() has happened and the closure might have been used by other
threads.

Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>
2023-10-30 21:48:22 -04:00
Kent Overstreet
2bce6368c4 closures: Better memory barriers
atomic_(dec|sub)_return_release() are a thing now - use them.

Also, delete the useless barrier in set_closure_fn(): it's redundant
with the memory barrier in closure_put(0.

Since closure_put() would now otherwise just have a release barrier, we
also need a new barrier when the ref hits 0 -
smp_acquire__after_ctrl_dep().

Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>
2023-10-30 21:48:22 -04:00
Kent Overstreet
b414e8ecd4 closures: Add a missing include
Fixes building in userspace.

Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>
2023-10-19 14:47:33 -04:00
Kent Overstreet
8c8d2d9670 bcache: move closures to lib/
Prep work for bcachefs - being a fork of bcache it also uses closures

Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>
Acked-by: Coly Li <colyli@suse.de>
Reviewed-by: Randy Dunlap <rdunlap@infradead.org>
2023-10-19 14:47:33 -04:00