From: Christophe Leroy <christophe.leroy@c-s.fr>
To: Benjamin Herrenschmidt <benh@kernel.crashing.org>,
Paul Mackerras <paulus@samba.org>,
Michael Ellerman <mpe@ellerman.id.au>
Cc: linux-kernel@vger.kernel.org, linuxppc-dev@lists.ozlabs.org
Subject: [PATCH 1/4] uaccess: Add user_read_access_begin/end and user_write_access_begin/end
Date: Tue, 4 Feb 2020 07:37:52 +0000 (UTC) [thread overview]
Message-ID: <f96ed94dc57ea810b738c4e02263e08c2c8781b6.1580801787.git.christophe.leroy@c-s.fr> (raw)
Some architectures like powerpc64 have the capability to separate
read access and write access protection.
For get_user() and copy_from_user(), powerpc64 only open read access.
For put_user() and copy_to_user(), powerpc64 only open write access.
But when using unsafe_get_user() or unsafe_put_user(),
user_access_begin open both read and write.
In order to avoid any risk based of hacking some variable parameters
passed to user_access_begin/end that would allow hacking and
leaving user access open or opening too much, it is preferable to
use dedicated static functions that can't be overridden.
Add a user_read_access_begin and user_read_access_end to only open
read access.
Add a user_write_access_begin and user_write_access_end to only open
write access.
By default, when undefined, those new access helpers default on the
existing user_access_begin and user_access_end.
Signed-off-by: Christophe Leroy <christophe.leroy@c-s.fr>
---
include/linux/uaccess.h | 8 ++++++++
1 file changed, 8 insertions(+)
diff --git a/include/linux/uaccess.h b/include/linux/uaccess.h
index 67f016010aad..9861c89f93be 100644
--- a/include/linux/uaccess.h
+++ b/include/linux/uaccess.h
@@ -378,6 +378,14 @@ extern long strnlen_unsafe_user(const void __user *unsafe_addr, long count);
static inline unsigned long user_access_save(void) { return 0UL; }
static inline void user_access_restore(unsigned long flags) { }
#endif
+#ifndef user_write_access_begin
+#define user_write_access_begin user_access_begin
+#define user_write_access_end user_access_end
+#endif
+#ifndef user_read_access_begin
+#define user_read_access_begin user_access_begin
+#define user_read_access_end user_access_end
+#endif
#ifdef CONFIG_HARDENED_USERCOPY
void usercopy_warn(const char *name, const char *detail, bool to_user,
--
2.25.0
next reply other threads:[~2020-02-04 7:37 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-02-04 7:37 Christophe Leroy [this message]
2020-02-04 7:37 ` [PATCH 2/4] uaccess: Selectively open read or write user access Christophe Leroy
2020-02-04 7:37 ` [PATCH 3/4] drm/i915/gem: Replace user_access_begin by user_write_access_begin Christophe Leroy
2020-02-04 7:37 ` [PATCH 4/4] powerpc/uaccess: Implement user_read_access_begin and user_write_access_begin Christophe Leroy
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