On Wed 26-06-19 16:11:21, 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.
Why do we want/need that? In other words the changelog should contina
WHY and WHAT. This one contains only the later one.
> Signed-off-by: Alastair D'Silva <alastair@xxxxxxxxxxx>
> ---
> drivers/base/memory.c | 18 +++++++++++++++---
> mm/sparse.c | 7 ++++++-
> 2 files changed, 21 insertions(+), 4 deletions(-)
>
> diff --git a/drivers/base/memory.c b/drivers/base/memory.c
> index f180427e48f4..9244c122abf1 100644
> --- a/drivers/base/memory.c
> +++ b/drivers/base/memory.c
> @@ -585,13 +585,21 @@ int __weak arch_get_memory_phys_device(unsigned long start_pfn)
> struct memory_block *find_memory_block_hinted(struct mem_section *section,
> struct memory_block *hint)
> {
> - int block_id = base_memory_block_id(__section_nr(section));
> + int block_id, section_nr;
> struct device *hintdev = hint ? &hint->dev : NULL;
> struct device *dev;
>
> + section_nr = __section_nr(section);
> + if (section_nr < 0) {
> + if (hintdev)
> + put_device(hintdev);
> + return NULL;
> + }
> +
> + block_id = base_memory_block_id(section_nr);
> dev = subsys_find_device_by_id(&memory_subsys, block_id, hintdev);
> - if (hint)
> - put_device(&hint->dev);
> + if (hintdev)
> + put_device(hintdev);
> if (!dev)
> return NULL;
> return to_memory_block(dev);
> @@ -664,6 +672,10 @@ static int init_memory_block(struct memory_block **memory,
> return -ENOMEM;
>
> scn_nr = __section_nr(section);
> +
> + if (scn_nr < 0)
> + return scn_nr;
> +
> mem->start_section_nr =
> base_memory_block_id(scn_nr) * sections_per_block;
> mem->end_section_nr = mem->start_section_nr + sections_per_block - 1;
> diff --git a/mm/sparse.c b/mm/sparse.c
> index fd13166949b5..57a1a3d9c1cf 100644
> --- a/mm/sparse.c
> +++ b/mm/sparse.c
> @@ -113,10 +113,15 @@ int __section_nr(struct mem_section* ms)
> continue;
>
> if ((ms >= root) && (ms < (root + SECTIONS_PER_ROOT)))
> - break;
> + break;
> }
>
> VM_BUG_ON(!root);
> + if (root_nr == NR_SECTION_ROOTS) {
> + VM_BUG_ON(true);
> +
> + return -EINVAL;
> + }
>
> return (root_nr * SECTIONS_PER_ROOT) + (ms - root);
> }
> --
> 2.21.0
--
Michal Hocko
SUSE Labs
