Re: [BUG] binfmt_elf: get_user() called in vma_dump_size() after set_fs(KERNEL_DS)

Yes, I suspect just surrounding the load with set_fs(USER_DS) and then
set_fs(KERNEL_DS) to put it back is likely the right thing to do.

Agreed.

The address is "safe" in that it does come from the vma, but we obviously
do play games with things like the call gate mappings etc.

gate_vma has VM_ALWAYSDUMP so it never sees this whole path anyway.
I doubt there is any actual case. But, point taken.

Should we also perhaps do this only if the vma is marked readable and
executable? That way we could avoid taking unnecessary faults there.

Probably doesn't really matter.

I'm sure it doesn't really matter. But, just to say it all: Requiring
VM_EXEC would actually exclude some valid cases. Even requiring VM_READ is
less than perfect as far as pedantic semantics go--but there is no reason
not to check it since its lack rules out get_user() actually working
anyway. I already chose that trade-off since get_user() here is so much
cheaper than get_user_pages(). The core dump from a stray
"mprotect(0,1UL<<32,PROT_NONE)" (i.e. presumably actually one with some
arithmetic error) would be useful if we made the check work without
VM_READ, but oh well.


Thanks,
Roland
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