On Mon, Jan 26, 2015 at 05:52:14PM +0300, Konstantin Khlebnikov wrote: > Lockless access to pte in pagemap_pte_range() might race with page migration > and trigger BUG_ON(!PageLocked()) in migration_entry_to_page(): > > CPU A (pagemap) CPU B (migration) > lock_page() > try_to_unmap(page, TTU_MIGRATION...) > make_migration_entry() > set_pte_at() > <read *pte> > pte_to_pagemap_entry() > remove_migration_ptes() > unlock_page() > if(is_migration_entry()) > migration_entry_to_page() > BUG_ON(!PageLocked(page)) > > Also lockless read might be non-atomic if pte is larger than wordsize. > Other pte walkers (smaps, numa_maps, clear_refs) already lock ptes. > > Signed-off-by: Konstantin Khlebnikov <khlebnikov@xxxxxxxxxxxxxx> > Reported-by: Andrey Ryabinin <a.ryabinin@xxxxxxxxxxx> > Fixes: 052fb0d635df ("proc: report file/anon bit in /proc/pid/pagemap") > Cc: Stable <stable@xxxxxxxxxxxxxxx> (v3.5+) Reviewed-by: Cyrill Gorcunov <gorcunov@xxxxxxxxxx> Thank you! -- To unsubscribe from this list: send the line "unsubscribe stable" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html