Re: [PATCH] kernel: fix data race in put_pid

Paul E. McKenney
2015-09-18T16:32:00Z

On Fri, Sep 18, 2015 at 10:57:32AM +0200, Peter Zijlstra wrote:
> On Fri, Sep 18, 2015 at 10:51:56AM +0200, Peter Zijlstra wrote:
> > That would upgrade the atomic_read() path to a full READ_ONCE_CTRL(),
> > and thereby avoid any of the kmem_cache_free() stores from leaking out.
>
> That said, on my TODO list is an item to review all atomic_{read,set}()
> implementation to ensure they're (at least) {READ,WRITE}_ONCE().
>
> A quick scan left me with this. There were indeed a few archs lacking
> READ_ONCE (or ACCESS_ONCE) for atomic_read() and hardly anybody used
> WRITE_ONCE() (or ACCESS_ONCE casting) for atomic_set().

You beat me to it! ;-)

When you get a signed-off version, please feel free to add my Acked-by.

Thanx, Paul

> ---
> arch/alpha/include/asm/atomic.h | 8 ++++----
> arch/arc/include/asm/atomic.h | 8 ++++----
> arch/arm/include/asm/atomic.h | 4 ++--
> arch/arm64/include/asm/atomic.h | 2 +-
> arch/avr32/include/asm/atomic.h | 4 ++--
> arch/frv/include/asm/atomic.h | 4 ++--
> arch/h8300/include/asm/atomic.h | 4 ++--
> arch/hexagon/include/asm/atomic.h | 2 +-
> arch/ia64/include/asm/atomic.h | 8 ++++----
> arch/m32r/include/asm/atomic.h | 4 ++--
> arch/m68k/include/asm/atomic.h | 4 ++--
> arch/metag/include/asm/atomic_lnkget.h | 3 ++-
> arch/metag/include/asm/atomic_lock1.h | 2 +-
> arch/mips/include/asm/atomic.h | 8 ++++----
> arch/mn10300/include/asm/atomic.h | 4 ++--
> arch/parisc/include/asm/atomic.h | 2 +-
> arch/sh/include/asm/atomic.h | 4 ++--
> arch/sparc/include/asm/atomic_64.h | 8 ++++----
> arch/tile/include/asm/atomic.h | 2 +-
> arch/tile/include/asm/atomic_64.h | 6 +++---
> arch/x86/include/asm/atomic.h | 4 ++--
> arch/x86/include/asm/atomic64_64.h | 4 ++--
> arch/xtensa/include/asm/atomic.h | 4 ++--
> include/asm-generic/atomic.h | 4 ++--
> 24 files changed, 54 insertions(+), 53 deletions(-)
>
> diff --git a/arch/alpha/include/asm/atomic.h b/arch/alpha/include/asm/atomic.h
> index e8c956098424..572b228c44c7 100644
> --- a/arch/alpha/include/asm/atomic.h
> +++ b/arch/alpha/include/asm/atomic.h
> @@ -17,11 +17,11 @@
> #define ATOMIC_INIT(i) { (i) }
> #define ATOMIC64_INIT(i) { (i) }
>
> -#define atomic_read(v) ACCESS_ONCE((v)->counter)
> -#define atomic64_read(v) ACCESS_ONCE((v)->counter)
> +#define atomic_read(v) READ_ONCE((v)->counter)
> +#define atomic64_read(v) READ_ONCE((v)->counter)
>
> -#define atomic_set(v,i) ((v)->counter = (i))
> -#define atomic64_set(v,i) ((v)->counter = (i))
> +#define atomic_set(v,i) WRITE_ONCE((v)->counter, (i))
> +#define atomic64_set(v,i) WRITE_ONCE((v)->counter, (i))
>
> /*
> * To get proper branch prediction for the main line, we must branch
> diff --git a/arch/arc/include/asm/atomic.h b/arch/arc/include/asm/atomic.h
> index c3ecda023e3a..7730d302cadb 100644
> --- a/arch/arc/include/asm/atomic.h
> +++ b/arch/arc/include/asm/atomic.h
> @@ -17,11 +17,11 @@
> #include <asm/barrier.h>
> #include <asm/smp.h>
>
> -#define atomic_read(v) ((v)->counter)
> +#define atomic_read(v) READ_ONCE((v)->counter)
>
> #ifdef CONFIG_ARC_HAS_LLSC
>
> -#define atomic_set(v, i) (((v)->counter) = (i))
> +#define atomic_set(v, i) WRITE_ONCE(((v)->counter), (i))
>
> #ifdef CONFIG_ARC_STAR_9000923308
>
> @@ -107,7 +107,7 @@ static inline int atomic_##op##_return(int i, atomic_t *v) \
> #ifndef CONFIG_SMP
>
> /* violating atomic_xxx API locking protocol in UP for optimization sake */
> -#define atomic_set(v, i) (((v)->counter) = (i))
> +#define atomic_set(v, i) WRITE_ONCE(((v)->counter), (i))
>
> #else
>
> @@ -125,7 +125,7 @@ static inline void atomic_set(atomic_t *v, int i)
> unsigned long flags;
>
> atomic_ops_lock(flags);
> - v->counter = i;
> + WRITE_ONCE(v->counter, i);
> atomic_ops_unlock(flags);
> }
>
> diff --git a/arch/arm/include/asm/atomic.h b/arch/arm/include/asm/atomic.h
> index fe3ef397f5a4..2bf80afb7841 100644
> --- a/arch/arm/include/asm/atomic.h
> +++ b/arch/arm/include/asm/atomic.h
> @@ -27,8 +27,8 @@
> * strex/ldrex monitor on some implementations. The reason we can use it for
> * atomic_set() is the clrex or dummy strex done on every exception return.
> */
> -#define atomic_read(v) ACCESS_ONCE((v)->counter)
> -#define atomic_set(v,i) (((v)->counter) = (i))
> +#define atomic_read(v) READ_ONCE((v)->counter)
> +#define atomic_set(v,i) WRITE_ONCE(((v)->counter), (i))
>
> #if __LINUX_ARM_ARCH__ >= 6
>
> diff --git a/arch/arm64/include/asm/atomic.h b/arch/arm64/include/asm/atomic.h
> index 35a67783cfa0..1e247ac2601a 100644
> --- a/arch/arm64/include/asm/atomic.h
> +++ b/arch/arm64/include/asm/atomic.h
> @@ -54,7 +54,7 @@
> #define ATOMIC_INIT(i) { (i) }
>
> #define atomic_read(v) READ_ONCE((v)->counter)
> -#define atomic_set(v, i) (((v)->counter) = (i))
> +#define atomic_set(v, i) WRITE_ONCE(((v)->counter), (i))
> #define atomic_xchg(v, new) xchg(&((v)->counter), (new))
> #define atomic_cmpxchg(v, old, new) cmpxchg(&((v)->counter), (old), (new))
>
> diff --git a/arch/avr32/include/asm/atomic.h b/arch/avr32/include/asm/atomic.h
> index 97c9bdf83409..d74fd8ce980a 100644
> --- a/arch/avr32/include/asm/atomic.h
> +++ b/arch/avr32/include/asm/atomic.h
> @@ -19,8 +19,8 @@
>
> #define ATOMIC_INIT(i) { (i) }
>
> -#define atomic_read(v) ACCESS_ONCE((v)->counter)
> -#define atomic_set(v, i) (((v)->counter) = i)
> +#define atomic_read(v) READ_ONCE((v)->counter)
> +#define atomic_set(v, i) WRITE_ONCE(((v)->counter), (i))
>
> #define ATOMIC_OP_RETURN(op, asm_op, asm_con) \
> static inline int __atomic_##op##_return(int i, atomic_t *v) \
> diff --git a/arch/frv/include/asm/atomic.h b/arch/frv/include/asm/atomic.h
> index 0da689def4cc..64f02d451aa8 100644
> --- a/arch/frv/include/asm/atomic.h
> +++ b/arch/frv/include/asm/atomic.h
> @@ -32,8 +32,8 @@
> */
>
> #define ATOMIC_INIT(i) { (i) }
> -#define atomic_read(v) ACCESS_ONCE((v)->counter)
> -#define atomic_set(v, i) (((v)->counter) = (i))
> +#define atomic_read(v) READ_ONCE((v)->counter)
> +#define atomic_set(v, i) WRITE_ONCE(((v)->counter), (i))
>
> static inline int atomic_inc_return(atomic_t *v)
> {
> diff --git a/arch/h8300/include/asm/atomic.h b/arch/h8300/include/asm/atomic.h
> index 702ee539f87d..4435a445ae7e 100644
> --- a/arch/h8300/include/asm/atomic.h
> +++ b/arch/h8300/include/asm/atomic.h
> @@ -11,8 +11,8 @@
>
> #define ATOMIC_INIT(i) { (i) }
>
> -#define atomic_read(v) ACCESS_ONCE((v)->counter)
> -#define atomic_set(v, i) (((v)->counter) = i)
> +#define atomic_read(v) READ_ONCE((v)->counter)
> +#define atomic_set(v, i) WRITE_ONCE(((v)->counter), (i))
>
> #include <linux/kernel.h>
>
> diff --git a/arch/hexagon/include/asm/atomic.h b/arch/hexagon/include/asm/atomic.h
> index 811d61f6422d..55696c4100d4 100644
> --- a/arch/hexagon/include/asm/atomic.h
> +++ b/arch/hexagon/include/asm/atomic.h
> @@ -48,7 +48,7 @@ static inline void atomic_set(atomic_t *v, int new)
> *
> * Assumes all word reads on our architecture are atomic.
> */
> -#define atomic_read(v) ((v)->counter)
> +#define atomic_read(v) READ_ONCE((v)->counter)
>
> /**
> * atomic_xchg - atomic
> diff --git a/arch/ia64/include/asm/atomic.h b/arch/ia64/include/asm/atomic.h
> index be4beeb77d57..8dfb5f6f6c35 100644
> --- a/arch/ia64/include/asm/atomic.h
> +++ b/arch/ia64/include/asm/atomic.h
> @@ -21,11 +21,11 @@
> #define ATOMIC_INIT(i) { (i) }
> #define ATOMIC64_INIT(i) { (i) }
>
> -#define atomic_read(v) ACCESS_ONCE((v)->counter)
> -#define atomic64_read(v) ACCESS_ONCE((v)->counter)
> +#define atomic_read(v) READ_ONCE((v)->counter)
> +#define atomic64_read(v) READ_ONCE((v)->counter)
>
> -#define atomic_set(v,i) (((v)->counter) = (i))
> -#define atomic64_set(v,i) (((v)->counter) = (i))
> +#define atomic_set(v,i) WRITE_ONCE(((v)->counter), (i))
> +#define atomic64_set(v,i) WRITE_ONCE(((v)->counter), (i))
>
> #define ATOMIC_OP(op, c_op) \
> static __inline__ int \
> diff --git a/arch/m32r/include/asm/atomic.h b/arch/m32r/include/asm/atomic.h
> index 025e2a170493..ea35160d632b 100644
> --- a/arch/m32r/include/asm/atomic.h
> +++ b/arch/m32r/include/asm/atomic.h
> @@ -28,7 +28,7 @@
> *
> * Atomically reads the value of @v.
> */
> -#define atomic_read(v) ACCESS_ONCE((v)->counter)
> +#define atomic_read(v) READ_ONCE((v)->counter)
>
> /**
> * atomic_set - set atomic variable
> @@ -37,7 +37,7 @@
> *
> * Atomically sets the value of @v to @i.
> */
> -#define atomic_set(v,i) (((v)->counter) = (i))
> +#define atomic_set(v,i) WRITE_ONCE(((v)->counter), (i))
>
> #ifdef CONFIG_CHIP_M32700_TS1
> #define __ATOMIC_CLOBBER , "r4"
> diff --git a/arch/m68k/include/asm/atomic.h b/arch/m68k/include/asm/atomic.h
> index 039fac120cc0..4858178260f9 100644
> --- a/arch/m68k/include/asm/atomic.h
> +++ b/arch/m68k/include/asm/atomic.h
> @@ -17,8 +17,8 @@
>
> #define ATOMIC_INIT(i) { (i) }
>
> -#define atomic_read(v) ACCESS_ONCE((v)->counter)
> -#define atomic_set(v, i) (((v)->counter) = i)
> +#define atomic_read(v) READ_ONCE((v)->counter)
> +#define atomic_set(v, i) WRITE_ONCE(((v)->counter), (i))
>
> /*
> * The ColdFire parts cannot do some immediate to memory operations,
> diff --git a/arch/metag/include/asm/atomic_lnkget.h b/arch/metag/include/asm/atomic_lnkget.h
> index 21c4c268b86c..1bd21c933435 100644
> --- a/arch/metag/include/asm/atomic_lnkget.h
> +++ b/arch/metag/include/asm/atomic_lnkget.h
> @@ -3,7 +3,8 @@
>
> #define ATOMIC_INIT(i) { (i) }
>
> -#define atomic_set(v, i) ((v)->counter = (i))
> +/* XXX: should be LNKSETD ? */
> +#define atomic_set(v, i) WRITE_ONCE((v)->counter, (i))
>
> #include <linux/compiler.h>
>
> diff --git a/arch/metag/include/asm/atomic_lock1.h b/arch/metag/include/asm/atomic_lock1.h
> index f8efe380fe8b..0295d9b8d5bf 100644
> --- a/arch/metag/include/asm/atomic_lock1.h
> +++ b/arch/metag/include/asm/atomic_lock1.h
> @@ -10,7 +10,7 @@
>
> static inline int atomic_read(const atomic_t *v)
> {
> - return (v)->counter;
> + return READ_ONCE((v)->counter);
> }
>
> /*
> diff --git a/arch/mips/include/asm/atomic.h b/arch/mips/include/asm/atomic.h
> index 4c42fd9af777..f82d3af07931 100644
> --- a/arch/mips/include/asm/atomic.h
> +++ b/arch/mips/include/asm/atomic.h
> @@ -30,7 +30,7 @@
> *
> * Atomically reads the value of @v.
> */
> -#define atomic_read(v) ACCESS_ONCE((v)->counter)
> +#define atomic_read(v) READ_ONCE((v)->counter)
>
> /*
> * atomic_set - set atomic variable
> @@ -39,7 +39,7 @@
> *
> * Atomically sets the value of @v to @i.
> */
> -#define atomic_set(v, i) ((v)->counter = (i))
> +#define atomic_set(v, i) WRITE_ONCE((v)->counter, (i))
>
> #define ATOMIC_OP(op, c_op, asm_op) \
> static __inline__ void atomic_##op(int i, atomic_t * v) \
> @@ -315,14 +315,14 @@ static __inline__ int __atomic_add_unless(atomic_t *v, int a, int u)
> * @v: pointer of type atomic64_t
> *
> */
> -#define atomic64_read(v) ACCESS_ONCE((v)->counter)
> +#define atomic64_read(v) READ_ONCE((v)->counter)
>
> /*
> * atomic64_set - set atomic variable
> * @v: pointer of type atomic64_t
> * @i: required value
> */
> -#define atomic64_set(v, i) ((v)->counter = (i))
> +#define atomic64_set(v, i) WRITE_ONCE((v)->counter, (i))
>
> #define ATOMIC64_OP(op, c_op, asm_op) \
> static __inline__ void atomic64_##op(long i, atomic64_t * v) \
> diff --git a/arch/mn10300/include/asm/atomic.h b/arch/mn10300/include/asm/atomic.h
> index 375e59140c9c..ce318d5ab23b 100644
> --- a/arch/mn10300/include/asm/atomic.h
> +++ b/arch/mn10300/include/asm/atomic.h
> @@ -34,7 +34,7 @@
> *
> * Atomically reads the value of @v. Note that the guaranteed
> */
> -#define atomic_read(v) (ACCESS_ONCE((v)->counter))
> +#define atomic_read(v) READ_ONCE((v)->counter)
>
> /**
> * atomic_set - set atomic variable
> @@ -43,7 +43,7 @@
> *
> * Atomically sets the value of @v to @i. Note that the guaranteed
> */
> -#define atomic_set(v, i) (((v)->counter) = (i))
> +#define atomic_set(v, i) WRITE_ONCE(((v)->counter), (i))
>
> #define ATOMIC_OP(op) \
> static inline void atomic_##op(int i, atomic_t *v) \
> diff --git a/arch/parisc/include/asm/atomic.h b/arch/parisc/include/asm/atomic.h
> index 2536965d00ea..1d109990a022 100644
> --- a/arch/parisc/include/asm/atomic.h
> +++ b/arch/parisc/include/asm/atomic.h
> @@ -67,7 +67,7 @@ static __inline__ void atomic_set(atomic_t *v, int i)
>
> static __inline__ int atomic_read(const atomic_t *v)
> {
> - return ACCESS_ONCE((v)->counter);
> + return READ_ONCE((v)->counter);
> }
>
> /* exported interface */
> diff --git a/arch/sh/include/asm/atomic.h b/arch/sh/include/asm/atomic.h
> index 05b9f74ce2d5..c399e1c55685 100644
> --- a/arch/sh/include/asm/atomic.h
> +++ b/arch/sh/include/asm/atomic.h
> @@ -14,8 +14,8 @@
>
> #define ATOMIC_INIT(i) { (i) }
>
> -#define atomic_read(v) ACCESS_ONCE((v)->counter)
> -#define atomic_set(v,i) ((v)->counter = (i))
> +#define atomic_read(v) READ_ONCE((v)->counter)
> +#define atomic_set(v,i) WRITE_ONCE((v)->counter, (i))
>
> #if defined(CONFIG_GUSA_RB)
> #include <asm/atomic-grb.h>
> diff --git a/arch/sparc/include/asm/atomic_64.h b/arch/sparc/include/asm/atomic_64.h
> index 917084ace49d..f2fbf9e16faf 100644
> --- a/arch/sparc/include/asm/atomic_64.h
> +++ b/arch/sparc/include/asm/atomic_64.h
> @@ -14,11 +14,11 @@
> #define ATOMIC_INIT(i) { (i) }
> #define ATOMIC64_INIT(i) { (i) }
>
> -#define atomic_read(v) ACCESS_ONCE((v)->counter)
> -#define atomic64_read(v) ACCESS_ONCE((v)->counter)
> +#define atomic_read(v) READ_ONCE((v)->counter)
> +#define atomic64_read(v) READ_ONCE((v)->counter)
>
> -#define atomic_set(v, i) (((v)->counter) = i)
> -#define atomic64_set(v, i) (((v)->counter) = i)
> +#define atomic_set(v, i) WRITE_ONCE(((v)->counter), (i))
> +#define atomic64_set(v, i) WRITE_ONCE(((v)->counter), (i))
>
> #define ATOMIC_OP(op) \
> void atomic_##op(int, atomic_t *); \
> diff --git a/arch/tile/include/asm/atomic.h b/arch/tile/include/asm/atomic.h
> index 709798460763..9fc0107a9c5e 100644
> --- a/arch/tile/include/asm/atomic.h
> +++ b/arch/tile/include/asm/atomic.h
> @@ -34,7 +34,7 @@
> */
> static inline int atomic_read(const atomic_t *v)
> {
> - return ACCESS_ONCE(v->counter);
> + return READ_ONCE(v->counter);
> }
>
> /**
> diff --git a/arch/tile/include/asm/atomic_64.h b/arch/tile/include/asm/atomic_64.h
> index 096a56d6ead4..51cabc26e387 100644
> --- a/arch/tile/include/asm/atomic_64.h
> +++ b/arch/tile/include/asm/atomic_64.h
> @@ -24,7 +24,7 @@
>
> /* First, the 32-bit atomic ops that are "real" on our 64-bit platform. */
>
> -#define atomic_set(v, i) ((v)->counter = (i))
> +#define atomic_set(v, i) WRITE_ONCE((v)->counter, (i))
>
> /*
> * The smp_mb() operations throughout are to support the fact that
> @@ -82,8 +82,8 @@ static inline void atomic_xor(int i, atomic_t *v)
>
> #define ATOMIC64_INIT(i) { (i) }
>
> -#define atomic64_read(v) ((v)->counter)
> -#define atomic64_set(v, i) ((v)->counter = (i))
> +#define atomic64_read(v) READ_ONCE((v)->counter)
> +#define atomic64_set(v, i) WRITE_ONCE((v)->counter, (i))
>
> static inline void atomic64_add(long i, atomic64_t *v)
> {
> diff --git a/arch/x86/include/asm/atomic.h b/arch/x86/include/asm/atomic.h
> index fb52aa644aab..ae5fb83e6d91 100644
> --- a/arch/x86/include/asm/atomic.h
> +++ b/arch/x86/include/asm/atomic.h
> @@ -24,7 +24,7 @@
> */
> static __always_inline int atomic_read(const atomic_t *v)
> {
> - return ACCESS_ONCE((v)->counter);
> + return READ_ONCE((v)->counter);
> }
>
> /**
> @@ -36,7 +36,7 @@ static __always_inline int atomic_read(const atomic_t *v)
> */
> static __always_inline void atomic_set(atomic_t *v, int i)
> {
> - v->counter = i;
> + WRITE_ONCE(v->counter, i);
> }
>
> /**
> diff --git a/arch/x86/include/asm/atomic64_64.h b/arch/x86/include/asm/atomic64_64.h
> index 50e33eff58de..037351022f54 100644
> --- a/arch/x86/include/asm/atomic64_64.h
> +++ b/arch/x86/include/asm/atomic64_64.h
> @@ -18,7 +18,7 @@
> */
> static inline long atomic64_read(const atomic64_t *v)
> {
> - return ACCESS_ONCE((v)->counter);
> + return READ_ONCE((v)->counter);
> }
>
> /**
> @@ -30,7 +30,7 @@ static inline long atomic64_read(const atomic64_t *v)
> */
> static inline void atomic64_set(atomic64_t *v, long i)
> {
> - v->counter = i;
> + WRITE_ONCE(v->counter, i);
> }
>
> /**
> diff --git a/arch/xtensa/include/asm/atomic.h b/arch/xtensa/include/asm/atomic.h
> index 93795d047303..fd8017ce298a 100644
> --- a/arch/xtensa/include/asm/atomic.h
> +++ b/arch/xtensa/include/asm/atomic.h
> @@ -47,7 +47,7 @@
> *
> * Atomically reads the value of @v.
> */
> -#define atomic_read(v) ACCESS_ONCE((v)->counter)
> +#define atomic_read(v) READ_ONCE((v)->counter)
>
> /**
> * atomic_set - set atomic variable
> @@ -56,7 +56,7 @@
> *
> * Atomically sets the value of @v to @i.
> */
> -#define atomic_set(v,i) ((v)->counter = (i))
> +#define atomic_set(v,i) WRITE_ONCE((v)->counter, (i))
>
> #if XCHAL_HAVE_S32C1I
> #define ATOMIC_OP(op) \
> diff --git a/include/asm-generic/atomic.h b/include/asm-generic/atomic.h
> index d4d7e337fdcb..74f1a3704d7a 100644
> --- a/include/asm-generic/atomic.h
> +++ b/include/asm-generic/atomic.h
> @@ -127,7 +127,7 @@ ATOMIC_OP(xor, ^)
> * Atomically reads the value of @v.
> */
> #ifndef atomic_read
> -#define atomic_read(v) ACCESS_ONCE((v)->counter)
> +#define atomic_read(v) READ_ONCE((v)->counter)
> #endif
>
> /**
> @@ -137,7 +137,7 @@ ATOMIC_OP(xor, ^)
> *
> * Atomically sets the value of @v to @i.
> */
> -#define atomic_set(v, i) (((v)->counter) = (i))
> +#define atomic_set(v, i) WRITE_ONCE(((v)->counter), (i))
>
> #include <linux/irqflags.h>
>
>