uprobes: __replace_page() should not use page_address_in_vma()
uprobes: __replace_page() should not use page_address_in_vma()

page_address_in_vma(old_page) in __replace_page() is ugly and
wrong. The caller already knows the correct virtual address,
this page was found by get_user_pages(vaddr).

However, page_address_in_vma() can actually fail if
page->mapping was cleared by __delete_from_page_cache() after
get_user_pages() returns. But this means the race with page
reclaim, write_opcode() should not fail, it should retry and
read this page again. Probably the race with remove_mapping() is
not possible due to page_freeze_refs() logic, but afaics at
least shmem_writepage()->shmem_delete_from_page_cache() can
clear ->mapping.

We could change __replace_page() to return -EAGAIN in this case,
but it would be better to simply use the caller's vaddr and rely
on page_check_address().

Signed-off-by: Oleg Nesterov <20b70f0af00562e63758b9ee42012ecc96c58590@redhat.com>
Acked-by: Srikar Dronamraju <srikar.vnet.ibm.com>
Cc: Anton Arapov <14deb5e5e417133e888bf47bb6a3555c9bb7d81c@redhat.com>
Cc: Srikar Dronamraju <1f69195f6d934d4caf5816234bde319316df237e@linux.vnet.ibm.com>
Link: c4a5e045b2c7b1434915819bf0270d0611049431@redhat.com
Signed-off-by: Ingo Molnar <9dbbbf0688fedc85ad4da37637f1a64b8c718ee2@kernel.org>

KristFoundation/Programs,KristFoundation/Programs,TeamVee-Kanas/android_kernel_samsung_kanas,KristFoundation/Programs,TeamVee-Kanas/android_kernel_samsung_kanas,KristFoundation/Programs,KristFoundation/Programs,TeamVee-Kanas/android_kernel_samsung_kanas,KristFoundation/Programs,TeamVee-Kanas/android_kernel_samsung_kanas,TeamVee-Kanas/android_kernel_samsung_kanas