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Date:   Wed, 20 Mar 2019 15:51:22 +0100
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Subject: [PATCH v13 08/20] fs, arm64: untag user pointers in fs/userfaultfd.c
From:   Andrey Konovalov <andreyknvl@google.com>
To:     Catalin Marinas <catalin.marinas@arm.com>,
        Will Deacon <will.deacon@arm.com>,
        Mark Rutland <mark.rutland@arm.com>,
        Robin Murphy <robin.murphy@arm.com>,
        Kees Cook <keescook@chromium.org>,
        Kate Stewart <kstewart@linuxfoundation.org>,
        Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        Andrew Morton <akpm@linux-foundation.org>,
        Ingo Molnar <mingo@kernel.org>,
        "Kirill A . Shutemov" <kirill.shutemov@linux.intel.com>,
        Shuah Khan <shuah@kernel.org>,
        Vincenzo Frascino <vincenzo.frascino@arm.com>,
        Eric Dumazet <edumazet@google.com>,
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        Alexei Starovoitov <ast@kernel.org>,
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Cc:     Dmitry Vyukov <dvyukov@google.com>,
        Kostya Serebryany <kcc@google.com>,
        Evgeniy Stepanov <eugenis@google.com>,
        Lee Smith <Lee.Smith@arm.com>,
        Ramana Radhakrishnan <Ramana.Radhakrishnan@arm.com>,
        Jacob Bramley <Jacob.Bramley@arm.com>,
        Ruben Ayrapetyan <Ruben.Ayrapetyan@arm.com>,
        Chintan Pandya <cpandya@codeaurora.org>,
        Luc Van Oostenryck <luc.vanoostenryck@gmail.com>,
        Dave Martin <Dave.Martin@arm.com>,
        Kevin Brodsky <kevin.brodsky@arm.com>,
        Szabolcs Nagy <Szabolcs.Nagy@arm.com>,
        Andrey Konovalov <andreyknvl@google.com>
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This patch is a part of a series that extends arm64 kernel ABI to allow to
pass tagged user pointers (with the top byte set to something else other
than 0x00) as syscall arguments.

userfaultfd_register() and userfaultfd_unregister() use provided user
pointers for vma lookups, which can only by done with untagged pointers.

Untag user pointers in these functions.

Signed-off-by: Andrey Konovalov <andreyknvl@google.com>
---
 fs/userfaultfd.c | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/fs/userfaultfd.c b/fs/userfaultfd.c
index 89800fc7dc9d..a3b70e0d9756 100644
--- a/fs/userfaultfd.c
+++ b/fs/userfaultfd.c
@@ -1320,6 +1320,9 @@ static int userfaultfd_register(struct userfaultfd_ctx *ctx,
 		goto out;
 	}
 
+	uffdio_register.range.start =
+		untagged_addr(uffdio_register.range.start);
+
 	ret = validate_range(mm, uffdio_register.range.start,
 			     uffdio_register.range.len);
 	if (ret)
@@ -1507,6 +1510,8 @@ static int userfaultfd_unregister(struct userfaultfd_ctx *ctx,
 	if (copy_from_user(&uffdio_unregister, buf, sizeof(uffdio_unregister)))
 		goto out;
 
+	uffdio_unregister.start = untagged_addr(uffdio_unregister.start);
+
 	ret = validate_range(mm, uffdio_unregister.start,
 			     uffdio_unregister.len);
 	if (ret)
-- 
2.21.0.225.g810b269d1ac-goog