From e96d71359e9bbea846a2111e4469a03a055dfa6f Mon Sep 17 00:00:00 2001
From: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Date: Mon, 9 Jul 2018 15:51:50 -0400
Subject: rseq: Use __u64 for rseq_cs fields, validate user inputs

Change the rseq ABI so rseq_cs start_ip, post_commit_offset and abort_ip
fields are seen as 64-bit fields by both 32-bit and 64-bit kernels rather
that ignoring the 32 upper bits on 32-bit kernels. This ensures we have a
consistent behavior for a 32-bit binary executed on 32-bit kernels and in
compat mode on 64-bit kernels.

Validating the value of abort_ip field to be below TASK_SIZE ensures the
kernel don't return to an invalid address when returning to userspace
after an abort. I don't fully trust each architecture code to consistently
deal with invalid return addresses.

Validating the value of the start_ip and post_commit_offset fields
prevents overflow on arithmetic performed on those values, used to
check whether abort_ip is within the rseq critical section.

If validation fails, the process is killed with a segmentation fault.

When the signature encountered before abort_ip does not match the expected
signature, return -EINVAL rather than -EPERM to be consistent with other
input validation return codes from rseq_get_rseq_cs().

Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Signed-off-by: Thomas 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/20180709195155.7654-2-mathieu.desnoyers@efficios.com
---
 include/uapi/linux/rseq.h | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

(limited to 'include')

diff --git a/include/uapi/linux/rseq.h b/include/uapi/linux/rseq.h
index d620fa43756c..519ad6e176d1 100644
--- a/include/uapi/linux/rseq.h
+++ b/include/uapi/linux/rseq.h
@@ -52,10 +52,10 @@ struct rseq_cs {
 	__u32 version;
 	/* enum rseq_cs_flags */
 	__u32 flags;
-	LINUX_FIELD_u32_u64(start_ip);
+	__u64 start_ip;
 	/* Offset from start_ip. */
-	LINUX_FIELD_u32_u64(post_commit_offset);
-	LINUX_FIELD_u32_u64(abort_ip);
+	__u64 post_commit_offset;
+	__u64 abort_ip;
 } __attribute__((aligned(4 * sizeof(__u64))));
 
 /*
-- 
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