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: Mathieu Desnoyers <[email protected]>
Signed-off-by: Thomas Gleixner <[email protected]>
Cc: [email protected]
Cc: Peter Zijlstra <[email protected]>
Cc: "Paul E . McKenney" <[email protected]>
Cc: Boqun Feng <[email protected]>
Cc: Andy Lutomirski <[email protected]>
Cc: Dave Watson <[email protected]>
Cc: Paul Turner <[email protected]>
Cc: Andrew Morton <[email protected]>
Cc: Russell King <[email protected]>
Cc: "H . Peter Anvin" <[email protected]>
Cc: Andi Kleen <[email protected]>
Cc: Chris Lameter <[email protected]>
Cc: Ben Maurer <[email protected]>
Cc: Steven Rostedt <[email protected]>
Cc: Josh Triplett <[email protected]>
Cc: Linus Torvalds <[email protected]>
Cc: Catalin Marinas <[email protected]>
Cc: Will Deacon <[email protected]>
Cc: Michael Kerrisk <[email protected]>
Cc: Joel Fernandes <[email protected]>
Cc: "Paul E. McKenney" <[email protected]>
Cc: "H. Peter Anvin" <[email protected]>
Link: https://lkml.kernel.org/r/[email protected]

1 files changed, 19 insertions, 8 deletions

diff --git a/include/uapi/linux/rseq.h b/include/uapi/linux/rseq.h
index bf4188c13bec..9a402fdb60e9 100644
--- a/include/uapi/linux/rseq.h
+++ b/include/uapi/linux/rseq.h
@@ -10,13 +10,8 @@
  * Copyright (c) 2015-2018 Mathieu Desnoyers <[email protected]>
  */
 
-#ifdef __KERNEL__
-# include <linux/types.h>
-#else
-# include <stdint.h>
-#endif
-
-#include <linux/types_32_64.h>
+#include <linux/types.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.
 	 *