Messages in this thread Patch in this message | | | Date | Fri, 26 May 2006 19:26:29 +0100 (BST) | From | Hugh Dickins <> | Subject | [PATCH mm] swapless page migration: fix fork corruption |
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Several times while testing swapless page migration, gcc has tried to exec a pointer instead of a string: smells like COW mappings are not being properly write-protected on fork.
The protection in copy_one_pte looks very convincing, until at last you realize that the second arg to make_migration_entry is a boolean "write", and SWP_MIGRATION_READ is 30.
Anyway, it's better done like in change_pte_range, using is_write_migration_entry and make_migration_entry_read.
Signed-off-by: Hugh Dickins <hugh@veritas.com> --- This is a fix to -mm's swapless-pm-add-r-w-migration-entries.patch
mm/memory.c | 9 +++------ 1 file changed, 3 insertions(+), 6 deletions(-)
--- 2.6.17-rc4-mm3/mm/memory.c 2006-05-22 12:19:00.000000000 +0100 +++ linux/mm/memory.c 2006-05-26 16:31:59.000000000 +0100 @@ -448,16 +448,13 @@ copy_one_pte(struct mm_struct *dst_mm, s &src_mm->mmlist); spin_unlock(&mmlist_lock); } - if (is_migration_entry(entry) && + if (is_write_migration_entry(entry) && is_cow_mapping(vm_flags)) { - page = migration_entry_to_page(entry); - /* * COW mappings require pages in both parent - * and child to be set to read. + * and child to be set to read. */ - entry = make_migration_entry(page, - SWP_MIGRATION_READ); + make_migration_entry_read(&entry); pte = swp_entry_to_pte(entry); set_pte_at(src_mm, addr, src_pte, pte); } - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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