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Commit ec9c82e0 authored by Mathieu Desnoyers's avatar Mathieu Desnoyers Committed by Thomas Gleixner
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rseq: uapi: Declare rseq_cs field as union, update includes 



Declaring the rseq_cs field as a union between __u64 and two __u32
allows both 32-bit and 64-bit kernels to read the full __u64, and
therefore validate that a 32-bit user-space cleared the upper 32
bits, thus ensuring a consistent behavior between native 32-bit
kernels and 32-bit compat tasks on 64-bit kernels.

Check that the rseq_cs value read is < TASK_SIZE.

The asm/byteorder.h header needs to be included by rseq.h, now
that it is not using linux/types_32_64.h anymore.

Considering that only __32 and __u64 types are declared in linux/rseq.h,
the linux/types.h header should always be included for both kernel and
user-space code: including stdint.h is just for u64 and u32, which are
not used in this header at all.

Use copy_from_user()/clear_user() to interact with a 64-bit field,
because arm32 does not implement 64-bit __get_user, and ppc32 does not
64-bit get_user. Considering that the rseq_cs pointer does not need to
be loaded/stored with single-copy atomicity from the kernel anymore, we
can simply use copy_from_user()/clear_user().

Signed-off-by: default avatarMathieu Desnoyers <mathieu.desnoyers@efficios.com>
Signed-off-by: default avatarThomas Gleixner <tglx@linutronix.de>
Cc: linux-api@vger.kernel.org
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: "Paul E . McKenney" <paulmck@linux.vnet.ibm.com>
Cc: Boqun Feng <boqun.feng@gmail.com>
Cc: Andy Lutomirski <luto@amacapital.net>
Cc: Dave Watson <davejwatson@fb.com>
Cc: Paul Turner <pjt@google.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Russell King <linux@arm.linux.org.uk>
Cc: "H . Peter Anvin" <hpa@zytor.com>
Cc: Andi Kleen <andi@firstfloor.org>
Cc: Chris Lameter <cl@linux.com>
Cc: Ben Maurer <bmaurer@fb.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Josh Triplett <josh@joshtriplett.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Will Deacon <will.deacon@arm.com>
Cc: Michael Kerrisk <mtk.manpages@gmail.com>
Cc: Joel Fernandes <joelaf@google.com>
Cc: "Paul E. McKenney" <paulmck@linux.vnet.ibm.com>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Link: https://lkml.kernel.org/r/20180709195155.7654-5-mathieu.desnoyers@efficios.com
parent 0fb9a1ab

include/uapi/linux/rseq.h

+19 −8
Original line number Diff line number Diff line
@@ -10,13 +10,8 @@ 
 * Copyright (c) 2015-2018 Mathieu Desnoyers <mathieu.desnoyers@efficios.com>

 */



#ifdef __KERNEL__

#include <linux/types.h>

#else

# include <stdint.h>

#endif



#include <linux/types_32_64.h>

#include <asm/byteorder.h>



enum rseq_cpu_id_state {

	RSEQ_CPU_ID_UNINITIALIZED		= -1,
@@ -111,7 +106,23 @@ struct rseq { 
	 * atomicity semantics. This field should only be updated by the

	 * thread which registered this data structure. Aligned on 64-bit.

	 */

	LINUX_FIELD_u32_u64(rseq_cs);

	union {

		__u64 ptr64;

#ifdef __LP64__

		__u64 ptr;

#else

		struct {

#if (defined(__BYTE_ORDER) && (__BYTE_ORDER == __BIG_ENDIAN)) || defined(__BIG_ENDIAN)

			__u32 padding;		/* Initialized to zero. */

			__u32 ptr32;

#else /* LITTLE */

			__u32 ptr32;

			__u32 padding;		/* Initialized to zero. */

#endif /* ENDIAN */

		} ptr;

#endif

	} rseq_cs;



	/*

	 * Restartable sequences flags field.

	 *

kernel/rseq.c

+9 −6
Original line number Diff line number Diff line
@@ -115,19 +115,20 @@ static int rseq_reset_rseq_cpu_id(struct task_struct *t) 
static int rseq_get_rseq_cs(struct task_struct *t, struct rseq_cs *rseq_cs)

{

	struct rseq_cs __user *urseq_cs;

	unsigned long ptr;

	u64 ptr;

	u32 __user *usig;

	u32 sig;

	int ret;



	ret = get_user(ptr, &t->rseq->rseq_cs);

	if (ret)

		return ret;

	if (copy_from_user(&ptr, &t->rseq->rseq_cs.ptr64, sizeof(ptr)))

		return -EFAULT;

	if (!ptr) {

		memset(rseq_cs, 0, sizeof(*rseq_cs));

		return 0;

	}

	urseq_cs = (struct rseq_cs __user *)ptr;

	if (ptr >= TASK_SIZE)

		return -EINVAL;

	urseq_cs = (struct rseq_cs __user *)(unsigned long)ptr;

	if (copy_from_user(rseq_cs, urseq_cs, sizeof(*rseq_cs)))

		return -EFAULT;
@@ -203,7 +204,9 @@ static int clear_rseq_cs(struct task_struct *t) 
	 *

	 * Set rseq_cs to NULL.

	 */

	return put_user(0UL, &t->rseq->rseq_cs);

	if (clear_user(&t->rseq->rseq_cs.ptr64, sizeof(t->rseq->rseq_cs.ptr64)))

		return -EFAULT;

	return 0;

}



/*

tools/testing/selftests/rseq/rseq.h

+10 −1
Original line number Diff line number Diff line
@@ -133,6 +133,15 @@ static inline uint32_t rseq_current_cpu(void) 
	return cpu;

}



static inline void rseq_clear_rseq_cs(void)

{

#ifdef __LP64__

	__rseq_abi.rseq_cs.ptr = 0;

#else

	__rseq_abi.rseq_cs.ptr.ptr32 = 0;

#endif

}



/*

 * rseq_prepare_unload() should be invoked by each thread using rseq_finish*()

 * at least once between their last rseq_finish*() and library unload of the
@@ -143,7 +152,7 @@ static inline uint32_t rseq_current_cpu(void) 
 */

static inline void rseq_prepare_unload(void)

{

	__rseq_abi.rseq_cs = 0;

	rseq_clear_rseq_cs();

}



#endif  /* RSEQ_H_ */