Re: [PATCH v7 03/25] ACPI / APEI: Switch estatus pool to use vmalloc memory

Borislav Petkov
2018-12-04T13:01:34Z

On Mon, Dec 03, 2018 at 06:05:51PM +0000, James Morse wrote:
> The ghes code is careful to parse and round firmware's advertised
> memory requirements for CPER records, up to a maximum of 64K.
> However when ghes_estatus_pool_expand() does its work, it splits
> the requested size into PAGE_SIZE granules.
>
> This means if firmware generates 5K of CPER records, and correctly
> describes this in the table, __process_error() will silently fail as it
> is unable to allocate more than PAGE_SIZE.
>
> Switch the estatus pool to vmalloc() memory. On x86 vmalloc() memory
> may fault and be fixed up by vmalloc_fault(). To prevent this call
> vmalloc_sync_all() before an NMI handler could discover the memory.
>
> Signed-off-by: James Morse <james.morse@arm.com>
> ---
> drivers/acpi/apei/ghes.c | 30 +++++++++++++++---------------
> 1 file changed, 15 insertions(+), 15 deletions(-)
>
> diff --git a/drivers/acpi/apei/ghes.c b/drivers/acpi/apei/ghes.c
> index e8503c7d721f..c15264f2dc4b 100644
> --- a/drivers/acpi/apei/ghes.c
> +++ b/drivers/acpi/apei/ghes.c
> @@ -170,40 +170,40 @@ static int ghes_estatus_pool_init(void)
> return 0;
> }
>
> -static void ghes_estatus_pool_free_chunk_page(struct gen_pool *pool,
> +static void ghes_estatus_pool_free_chunk(struct gen_pool *pool,
> struct gen_pool_chunk *chunk,
> void *data)
> {
> - free_page(chunk->start_addr);
> + vfree((void *)chunk->start_addr);
> }
>
> static void ghes_estatus_pool_exit(void)
> {
> gen_pool_for_each_chunk(ghes_estatus_pool,
> - ghes_estatus_pool_free_chunk_page, NULL);
> + ghes_estatus_pool_free_chunk, NULL);
> gen_pool_destroy(ghes_estatus_pool);
> }
>
> static int ghes_estatus_pool_expand(unsigned long len)
> {
> - unsigned long i, pages, size, addr;
> - int ret;
> + unsigned long size, addr;
>
> ghes_estatus_pool_size_request += PAGE_ALIGN(len);

So here we increment with page-aligned len...

> size = gen_pool_size(ghes_estatus_pool);
> if (size >= ghes_estatus_pool_size_request)
> return 0;
> - pages = (ghes_estatus_pool_size_request - size) / PAGE_SIZE;
> - for (i = 0; i < pages; i++) {
> - addr = __get_free_page(GFP_KERNEL);
> - if (!addr)
> - return -ENOMEM;
> - ret = gen_pool_add(ghes_estatus_pool, addr, PAGE_SIZE, -1);
> - if (ret)
> - return ret;
> - }
>
> - return 0;
> + addr = (unsigned long)vmalloc(PAGE_ALIGN(len));
> + if (!addr)
> + return -ENOMEM;

... and if we return here due to the ENOMEM, that increment above
remains.

I see you're reworking all that stuff in the next patches which is cool,
thx. So I guess we should leave it as is, as the code before was broken
too.

IOW,

Reviewed-by: Borislav Petkov <bp@suse.de>

--
Regards/Gruss,
Boris.

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