On Mon, Jun 17, 2019 at 02:36:27PM +1000, Alastair D'Silva wrote:
> From: Alastair D'Silva <alastair@xxxxxxxxxxx>
>
> If a memory section comes in where the physical address is greater than
> that which is managed by the kernel, this function would not trigger the
> bug and instead return a bogus section number.
>
> This patch tracks whether the section was actually found, and triggers the
> bug if not.
>
> Signed-off-by: Alastair D'Silva <alastair@xxxxxxxxxxx>
> ---
> mm/sparse.c | 13 ++++++++-----
> 1 file changed, 8 insertions(+), 5 deletions(-)
>
> diff --git a/mm/sparse.c b/mm/sparse.c
> index fd13166949b5..104a79fedd00 100644
> --- a/mm/sparse.c
> +++ b/mm/sparse.c
> @@ -105,20 +105,23 @@ static inline int sparse_index_init(unsigned long section_nr, int nid)
> int __section_nr(struct mem_section* ms)
> {
> unsigned long root_nr;
> - struct mem_section *root = NULL;
> + struct mem_section *found = NULL;
> + struct mem_section *root;
>
> for (root_nr = 0; root_nr < NR_SECTION_ROOTS; root_nr++) {
> root = __nr_to_section(root_nr * SECTIONS_PER_ROOT);
> if (!root)
> continue;
>
> - if ((ms >= root) && (ms < (root + SECTIONS_PER_ROOT)))
> - break;
> + if ((ms >= root) && (ms < (root + SECTIONS_PER_ROOT))) {
> + found = root;
> + break;
> + }
> }
>
> - VM_BUG_ON(!root);
> + VM_BUG_ON(!found);
Isn't it enough to check for root_nr == NR_SECTION_ROOTS?
>
> - return (root_nr * SECTIONS_PER_ROOT) + (ms - root);
> + return (root_nr * SECTIONS_PER_ROOT) + (ms - found);
It'll still return a bogus section number with CONFIG_DEBUG_VM=n
> }
> #else
> int __section_nr(struct mem_section* ms)
> --
> 2.21.0
>
--
Sincerely yours,
Mike.
