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Breno Leitao
512db8267b
rds_info_getsockopt() pins the destination user pages with FOLL_WRITE and
the RDS_INFO_* producers memcpy the snapshot into them through
kmap_atomic(). Because that copy goes through the kernel direct map, the
dirty bit on the user PTE is never set, so unpin_user_pages() releases the
pages without marking them dirty. A file-backed destination page can then
be reclaimed without writeback, silently discarding the copied data.
Use unpin_user_pages_dirty_lock() with make_dirty=true so the modified
pages are marked dirty before they are unpinned.
Fixes: a8c879a7ee ("RDS: Info and stats")
Signed-off-by: Breno Leitao <[email protected]>
Reviewed-by: Allison Henderson <[email protected]>
Link: https://patch.msgid.link/[email protected]
Signed-off-by: Jakub Kicinski <[email protected]>