[RFC][PATCH 02/14] x86_64: csum_..._copy_..._user(): switch to unsafe_..._user()

Al Viro
2020-03-27T23:31:55Z

We already have stac/clac pair around the calls of csum_partial_copy_generic().
Stretch that area back, so that it covers the preceding loop (and convert
the loop body from __{get,put}_user() to unsafe_{get,put}_user()).
That brings the beginning of the areas to the earlier access_ok(),
which allows to convert them into user_access_{begin,end}() ones.

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
---
arch/x86/lib/csum-wrappers_64.c | 23 ++++++++++++-----------
1 file changed, 12 insertions(+), 11 deletions(-)

diff --git a/arch/x86/lib/csum-wrappers_64.c b/arch/x86/lib/csum-wrappers_64.c
index 875c2f5968a0..90d02c82bb7a 100644
--- a/arch/x86/lib/csum-wrappers_64.c
+++ b/arch/x86/lib/csum-wrappers_64.c
@@ -27,7 +27,7 @@ csum_partial_copy_from_user(const void __user *src, void *dst,
might_sleep();
*errp = 0;

- if (!likely(access_ok(src, len)))
+ if (!likely(user_access_begin(src, len)))
goto out_err;

/*
@@ -42,8 +42,7 @@ csum_partial_copy_from_user(const void __user *src, void *dst,
while (((unsigned long)src & 6) && len >= 2) {
__u16 val16;

- if (__get_user(val16, (const __u16 __user *)src))
- goto out_err;
+ unsafe_get_user(val16, (const __u16 __user *)src, out);

*(__u16 *)dst = val16;
isum = (__force __wsum)add32_with_carry(
@@ -53,15 +52,16 @@ csum_partial_copy_from_user(const void __user *src, void *dst,
len -= 2;
}
}
- stac();
isum = csum_partial_copy_generic((__force const void *)src,
dst, len, isum, errp, NULL);
- clac();
+ user_access_end();
if (unlikely(*errp))
goto out_err;

return isum;

+out:
+ user_access_end();
out_err:
*errp = -EFAULT;
memset(dst, 0, len);
@@ -89,7 +89,7 @@ csum_and_copy_to_user(const void *src, void __user *dst,

might_sleep();

- if (unlikely(!access_ok(dst, len))) {
+ if (unlikely(!user_access_begin(dst, len))) {
*errp = -EFAULT;
return 0;
}
@@ -100,9 +100,7 @@ csum_and_copy_to_user(const void *src, void __user *dst,

isum = (__force __wsum)add32_with_carry(
(__force unsigned)isum, val16);
- *errp = __put_user(val16, (__u16 __user *)dst);
- if (*errp)
- return isum;
+ unsafe_put_user(val16, (__u16 __user *)dst, out);
src += 2;
dst += 2;
len -= 2;
@@ -110,11 +108,14 @@ csum_and_copy_to_user(const void *src, void __user *dst,
}

*errp = 0;
- stac();
ret = csum_partial_copy_generic(src, (void __force *)dst,
len, isum, NULL, errp);
- clac();
+ user_access_end();
return ret;
+out:
+ user_access_end();
+ *errp = -EFAULT;
+ return isum;
}
EXPORT_SYMBOL(csum_and_copy_to_user);

--
2.11.0