On Mon, 29 Jun, at 11:21:07AM, Luck, Tony wrote:
> The memory error record structure includes as its first field a
> bitmask of which subsequent fields are valid. The allows new fields
> to be added to the structure while keeping compatibility with older
> software that parses these records. This mechanism was used between
> versions 2.2 and 2.3 to add four new fields, growing the size of the
> structure from 73 bytes to 80. But Linux just added all the new
> fields so this test:
> if (gdata->error_data_length >= sizeof(*mem_err))
> cper_print_mem(newpfx, mem_err);
> else
> goto err_section_too_small;
> now make Linux complain about old format records being too short.
>
> Add a definition for the old format of the structure and use that
> for the minimum size check. Pass the actual size to cper_print_mem()
> so it can sanity check the validation_bits field to ensure that if
> a BIOS using the old format sets bits as if it were new, we won't
> access fields beyond the end of the structure.
>
> Signed-off-by: Tony Luck <tony.luck@xxxxxxxxx>
> ---
> drivers/firmware/efi/cper.c | 13 ++++++++++---
> include/linux/cper.h | 22 +++++++++++++++++++++-
> 2 files changed, 31 insertions(+), 4 deletions(-)
>
> diff --git a/drivers/firmware/efi/cper.c b/drivers/firmware/efi/cper.c
> index 4fd9961d552e..b2012004a8ab 100644
> --- a/drivers/firmware/efi/cper.c
> +++ b/drivers/firmware/efi/cper.c
> @@ -305,10 +305,15 @@ const char *cper_mem_err_unpack(struct trace_seq *p,
> return ret;
> }
>
> -static void cper_print_mem(const char *pfx, const struct cper_sec_mem_err *mem)
> +static void cper_print_mem(const char *pfx, const struct cper_sec_mem_err *mem,
> + int len)
> {
> struct cper_mem_err_compact cmem;
>
> + /* Don't trust UEFI 2.1/2.2 structure with bad validation bits */
> + if (len == sizeof(struct cper_sec_mem_err_old) &&
> + (mem->validation_bits & ~(CPER_MEM_VALID_RANK_NUMBER - 1)))
> + return;
I would have thought that we'd want to print an error message here
instead of silently returning?
Otherwise looks good.
--
Matt Fleming, Intel Open Source Technology Center
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