linux-kernel - [PATCH v2 3/5] drm/i915/gem: Replace user_access_begin by user_write_access

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Message-Id: <ebf1250b6d4f351469fb339e5399d8b92aa8a1c1.1585898438.git.christophe.leroy@c-s.fr>
Date:   Fri,  3 Apr 2020 07:20:52 +0000 (UTC)
From:   Christophe Leroy <christophe.leroy@....fr>
To:     Benjamin Herrenschmidt <benh@...nel.crashing.org>,
        Paul Mackerras <paulus@...ba.org>,
        Michael Ellerman <mpe@...erman.id.au>, airlied@...ux.ie,
        daniel@...ll.ch, torvalds@...ux-foundation.org,
        viro@...iv.linux.org.uk, akpm@...ux-foundation.org,
        keescook@...omium.org, hpa@...or.com
Cc:     linux-kernel@...r.kernel.org, linuxppc-dev@...ts.ozlabs.org,
        linux-mm@...ck.org, linux-arch@...r.kernel.org,
        intel-gfx@...ts.freedesktop.org
Subject: [PATCH v2 3/5] drm/i915/gem: Replace user_access_begin by
 user_write_access_begin

When i915_gem_execbuffer2_ioctl() is using user_access_begin(),
that's only to perform unsafe_put_user() so use
user_write_access_begin() in order to only open write access.

Signed-off-by: Christophe Leroy <christophe.leroy@....fr>
Reviewed-by: Kees Cook <keescook@...omium.org>
---
v2: Rebased (one part of the patch flies away)
---
 drivers/gpu/drm/i915/gem/i915_gem_execbuffer.c | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/drivers/gpu/drm/i915/gem/i915_gem_execbuffer.c b/drivers/gpu/drm/i915/gem/i915_gem_execbuffer.c
index 36d069504836..b4c903308590 100644
--- a/drivers/gpu/drm/i915/gem/i915_gem_execbuffer.c
+++ b/drivers/gpu/drm/i915/gem/i915_gem_execbuffer.c
@@ -2794,7 +2794,8 @@ i915_gem_execbuffer2_ioctl(struct drm_device *dev, void *data,
 		 * And this range already got effectively checked earlier
 		 * when we did the "copy_from_user()" above.
 		 */
-		if (!user_access_begin(user_exec_list, count * sizeof(*user_exec_list)))
+		if (!user_write_access_begin(user_exec_list,
+					     count * sizeof(*user_exec_list)))
 			goto end;
 
 		for (i = 0; i < args->buffer_count; i++) {
@@ -2808,7 +2809,7 @@ i915_gem_execbuffer2_ioctl(struct drm_device *dev, void *data,
 					end_user);
 		}
 end_user:
-		user_access_end();
+		user_write_access_end();
 end:;
 	}
 
-- 
2.25.0