mm: Make copy_from_user() in migrate.c statically predictable
x86-32 has had a static test for copy_on_user() overflow for a while. This test currently fails in mm/migrate.c resulting in an allyesconfig/allmodconfig build failure on x86-32: In function ‘copy_from_user’, inlined from ‘do_pages_stat’ at /home/hpa/kernel/git/mm/migrate.c:1012: /home/hpa/kernel/git/arch/x86/include/asm/uaccess_32.h:212: error: call to ‘copy_from_user_overflow’ declared Make the logic more explicit and therefore easier for gcc to understand. v2: rewrite the loop entirely using a more normal structure for a chunked-data loop (Linus Torvalds) Reported-by: Len Brown <lenb@kernel.org> Signed-off-by: H. Peter Anvin <hpa@zytor.com> Reviewed-and-Tested-by: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com> Cc: Arjan van de Ven <arjan@linux.kernel.org> Cc: Andrew Morton <akpm@linux-foundation.org> Cc: Christoph Lameter <cl@linux-foundation.org> Cc: Hugh Dickins <hugh.dickins@tiscali.co.uk> Cc: Rik van Riel <riel@redhat.com> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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36
mm/migrate.c
36
mm/migrate.c
@ -1002,33 +1002,27 @@ static int do_pages_stat(struct mm_struct *mm, unsigned long nr_pages,
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#define DO_PAGES_STAT_CHUNK_NR 16
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const void __user *chunk_pages[DO_PAGES_STAT_CHUNK_NR];
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int chunk_status[DO_PAGES_STAT_CHUNK_NR];
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unsigned long i, chunk_nr = DO_PAGES_STAT_CHUNK_NR;
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int err;
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for (i = 0; i < nr_pages; i += chunk_nr) {
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if (chunk_nr > nr_pages - i)
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chunk_nr = nr_pages - i;
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while (nr_pages) {
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unsigned long chunk_nr;
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err = copy_from_user(chunk_pages, &pages[i],
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chunk_nr * sizeof(*chunk_pages));
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if (err) {
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err = -EFAULT;
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goto out;
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}
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chunk_nr = nr_pages;
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if (chunk_nr > DO_PAGES_STAT_CHUNK_NR)
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chunk_nr = DO_PAGES_STAT_CHUNK_NR;
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if (copy_from_user(chunk_pages, pages, chunk_nr * sizeof(*chunk_pages)))
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break;
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do_pages_stat_array(mm, chunk_nr, chunk_pages, chunk_status);
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err = copy_to_user(&status[i], chunk_status,
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chunk_nr * sizeof(*chunk_status));
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if (err) {
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err = -EFAULT;
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goto out;
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}
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}
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err = 0;
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if (copy_to_user(status, chunk_status, chunk_nr * sizeof(*status)))
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break;
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out:
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return err;
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pages += chunk_nr;
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status += chunk_nr;
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nr_pages -= chunk_nr;
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}
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return nr_pages ? -EFAULT : 0;
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}
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/*
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