On Tue, Jan 14, 2020 at 12:09 PM Vineet Gupta
<Vineet.Gupta1@xxxxxxxxxxxx> wrote:
>
> There are 2 generic varaints of strncpy_from_user() / strnlen_user()
> (1). inline version in asm-generic/uaccess.h
I think we should get rid of this entirely. It's just a buggy garbage
implementation that nobody should ever actually use.
It does just about everything wrong that you *can* do, wrong,
including doing the NUL-filling termination of standard strncpy() that
"strncpy_from_user()" doesn't actually do.
So:
- the asm-generic/uaccess.h __strncpy_from_user() function is just
horribly wrong
- the generic/uaccess.h version of strncpy_from_user() shouldn't be
an inline function either, since the only thing it can do inline is
the bogus one-byte access check that _barely_ makes security work (you
also need to have a guard page to _actually_ make it work, and I'm not
atr all convinced that people do).
the whole thing is just broken and should be removed from a header file.
> (2). optimized word-at-a-time version in lib/*
That is - outside of the original x86 strncpy_from_user() - the only
copy of this function that historically gets all the corner cases
right. And even those we've gotten wrong occasionally.
I would suggest that anybody who uses asm-generic/uaccess.h needs to
simply use the generic library version.
Linus
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