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uaccess: Selectively open read or write user access

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When opening user access to only perform reads, only open read access.
When opening user access to only perform writes, only open write
access.

Signed-off-by: Christophe Leroy <christophe.leroy@c-s.fr>
Reviewed-by: Kees Cook <keescook@chromium.org>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/2e73bc57125c2c6ab12a587586a4eed3a47105fc.1585898438.git.christophe.leroy@c-s.fr
This commit is contained in:
Christophe Leroy
2020-04-03 07:20:51 +00:00
committed by Michael Ellerman
parent 999a22890c
commit 41cd780524
6 changed files with 25 additions and 25 deletions
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6
lib/usercopy.c
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@@ -58,7 +58,7 @@ int check_zeroed_user(const void __user *from, size_t size)
from -= align;
size += align;
if (!user_access_begin(from, size))
if (!user_read_access_begin(from, size))
return -EFAULT;
unsafe_get_user(val, (unsigned long __user *) from, err_fault);
@@ -79,10 +79,10 @@ int check_zeroed_user(const void __user *from, size_t size)
val &= aligned_byte_mask(size);
done:
user_access_end();
user_read_access_end();
return (val == 0);
err_fault:
user_access_end();
user_read_access_end();
return -EFAULT;
}
EXPORT_SYMBOL(check_zeroed_user);