Re: [PATCH v1 1/4] lib: introduce copy_struct_from_user() helper
flat view
From: Linus Torvalds <torvalds@linux-foundation.org>
Date: 2019-09-25 17:11:00
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lkml
On Wed, Sep 25, 2019 at 10:00 AM Aleksa Sarai [off-list ref] wrote:
+int is_zeroed_user(const void __user *from, size_t size)
I like how you've done this, but it's buggy and only works on 64-bit. All the "u64" and "8" cases need to be "unsigned long" and "sizeof(unsigned long)". Part of that requirement is:
+ unsafe_get_user(val, (u64 __user *) from, err_fault);
This part works fine - although 64-bit accesses migth be much more expensive and the win of unrolling might not be sufficient - but:
quoted hunk ↗ jump to hunk
+ if (align) { + /* @from is unaligned. */ + val &= ~aligned_byte_mask(align); + align = 0; + }
This part fundamentally only works on 'unsigned long'.
Linus