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locking/refcount: Create unchecked atomic_t implementation

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Many subsystems will not use refcount_t unless there is a way to build the
kernel so that there is no regression in speed compared to atomic_t. This
adds CONFIG_REFCOUNT_FULL to enable the full refcount_t implementation
which has the validation but is slightly slower. When not enabled,
refcount_t uses the basic unchecked atomic_t routines, which results in
no code changes compared to just using atomic_t directly.

Signed-off-by: Kees Cook <[email protected]>
Acked-by: Greg Kroah-Hartman <[email protected]>
Cc: Alexey Dobriyan <[email protected]>
Cc: Andrew Morton <[email protected]>
Cc: Arnd Bergmann <[email protected]>
Cc: Christoph Hellwig <[email protected]>
Cc: David S. Miller <[email protected]>
Cc: David Windsor <[email protected]>
Cc: Davidlohr Bueso <[email protected]>
Cc: Elena Reshetova <[email protected]>
Cc: Eric Biggers <[email protected]>
Cc: Eric W. Biederman <[email protected]>
Cc: Hans Liljestrand <[email protected]>
Cc: James Bottomley <[email protected]>
Cc: Jann Horn <[email protected]>
Cc: Josh Poimboeuf <[email protected]>
Cc: Linus Torvalds <[email protected]>
Cc: Manfred Spraul <[email protected]>
Cc: Peter Zijlstra <[email protected]>
Cc: Rik van Riel <[email protected]>
Cc: Serge E. Hallyn <[email protected]>
Cc: Thomas Gleixner <[email protected]>
Cc: [email protected]
Cc: [email protected]
Cc: linux-arch <[email protected]>
Link: http://lkml.kernel.org/r/20170621200026.GA115679@beast
Signed-off-by: Ingo Molnar <[email protected]>
This commit is contained in:
Kees Cook 2017-06-21 13:00:26 -07:00 • committed by Ingo Molnar
commit fd25d19f6b
3 changed files with 54 additions and 0 deletions
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9
arch/Kconfig
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@ -867,4 +867,13 @@ config STRICT_MODULE_RWX
config ARCH_WANT_RELAX_ORDER
bool
config REFCOUNT_FULL
bool "Perform full reference count validation at the expense of speed"
help
Enabling this switches the refcounting infrastructure from a fast
unchecked atomic_t implementation to a fully state checked
implementation, which can be (slightly) slower but provides protections
against various use-after-free conditions that can be used in
security flaw exploits.
source "kernel/gcov/Kconfig"