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Date: Fri, 16 Aug 2019 16:49:10 -0400
From: Jeff Moyer <jmoyer@...hat.com>
To: Dan Williams <dan.j.williams@...el.com>
Cc: linux-nvdimm@...ts.01.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 2/3] libnvdimm/security: Tighten scope of nvdimm->busy vs security operations
Dan Williams <dan.j.williams@...el.com> writes:
> The blanket blocking of all security operations while the DIMM is in
> active use in a region is too restrictive. The only security operations
> that need to be aware of the ->busy state are those that mutate the
> state of data, i.e. erase and overwrite.
>
> Refactor the ->busy checks to be applied at the entry common entry point
> in __security_store() rather than each of the helper routines.
I'm not sure this buys you much. Did you test this on actual hardware
to make sure your assumptions are correct? I guess the worst case is we
get an "invalid security state" error back from the firmware....
Still, what's the motivation for this?
-Jeff
>
> Cc: Dave Jiang <dave.jiang@...el.com>
> Signed-off-by: Dan Williams <dan.j.williams@...el.com>
> ---
> drivers/nvdimm/dimm_devs.c | 33 ++++++++++++++++-----------------
> drivers/nvdimm/security.c | 10 ----------
> 2 files changed, 16 insertions(+), 27 deletions(-)
>
> diff --git a/drivers/nvdimm/dimm_devs.c b/drivers/nvdimm/dimm_devs.c
> index 53330625fe07..d837cb9be83d 100644
> --- a/drivers/nvdimm/dimm_devs.c
> +++ b/drivers/nvdimm/dimm_devs.c
> @@ -424,9 +424,6 @@ static ssize_t __security_store(struct device *dev, const char *buf, size_t len)
> unsigned int key, newkey;
> int i;
>
> - if (atomic_read(&nvdimm->busy))
> - return -EBUSY;
> -
> rc = sscanf(buf, "%"__stringify(SEC_CMD_SIZE)"s"
> " %"__stringify(KEY_ID_SIZE)"s"
> " %"__stringify(KEY_ID_SIZE)"s",
> @@ -451,23 +448,25 @@ static ssize_t __security_store(struct device *dev, const char *buf, size_t len)
> } else if (i == OP_DISABLE) {
> dev_dbg(dev, "disable %u\n", key);
> rc = nvdimm_security_disable(nvdimm, key);
> - } else if (i == OP_UPDATE) {
> - dev_dbg(dev, "update %u %u\n", key, newkey);
> - rc = nvdimm_security_update(nvdimm, key, newkey, NVDIMM_USER);
> - } else if (i == OP_ERASE) {
> - dev_dbg(dev, "erase %u\n", key);
> - rc = nvdimm_security_erase(nvdimm, key, NVDIMM_USER);
> + } else if (i == OP_UPDATE || i == OP_MASTER_UPDATE) {
> + dev_dbg(dev, "%s %u %u\n", ops[i].name, key, newkey);
> + rc = nvdimm_security_update(nvdimm, key, newkey, i == OP_UPDATE
> + ? NVDIMM_USER : NVDIMM_MASTER);
> + } else if (i == OP_ERASE || i == OP_MASTER_ERASE) {
> + dev_dbg(dev, "%s %u\n", ops[i].name, key);
> + if (atomic_read(&nvdimm->busy)) {
> + dev_dbg(dev, "Unable to secure erase while DIMM active.\n");
> + return -EBUSY;
> + }
> + rc = nvdimm_security_erase(nvdimm, key, i == OP_ERASE
> + ? NVDIMM_USER : NVDIMM_MASTER);
> } else if (i == OP_OVERWRITE) {
> dev_dbg(dev, "overwrite %u\n", key);
> + if (atomic_read(&nvdimm->busy)) {
> + dev_dbg(dev, "Unable to overwrite while DIMM active.\n");
> + return -EBUSY;
> + }
> rc = nvdimm_security_overwrite(nvdimm, key);
> - } else if (i == OP_MASTER_UPDATE) {
> - dev_dbg(dev, "master_update %u %u\n", key, newkey);
> - rc = nvdimm_security_update(nvdimm, key, newkey,
> - NVDIMM_MASTER);
> - } else if (i == OP_MASTER_ERASE) {
> - dev_dbg(dev, "master_erase %u\n", key);
> - rc = nvdimm_security_erase(nvdimm, key,
> - NVDIMM_MASTER);
> } else
> return -EINVAL;
>
> diff --git a/drivers/nvdimm/security.c b/drivers/nvdimm/security.c
> index 5862d0eee9db..2166e627383a 100644
> --- a/drivers/nvdimm/security.c
> +++ b/drivers/nvdimm/security.c
> @@ -334,11 +334,6 @@ int nvdimm_security_erase(struct nvdimm *nvdimm, unsigned int keyid,
> || !nvdimm->sec.flags)
> return -EOPNOTSUPP;
>
> - if (atomic_read(&nvdimm->busy)) {
> - dev_dbg(dev, "Unable to secure erase while DIMM active.\n");
> - return -EBUSY;
> - }
> -
> rc = check_security_state(nvdimm);
> if (rc)
> return rc;
> @@ -380,11 +375,6 @@ int nvdimm_security_overwrite(struct nvdimm *nvdimm, unsigned int keyid)
> || !nvdimm->sec.flags)
> return -EOPNOTSUPP;
>
> - if (atomic_read(&nvdimm->busy)) {
> - dev_dbg(dev, "Unable to overwrite while DIMM active.\n");
> - return -EBUSY;
> - }
> -
> if (dev->driver == NULL) {
> dev_dbg(dev, "Unable to overwrite while DIMM active.\n");
> return -EINVAL;
>
> _______________________________________________
> Linux-nvdimm mailing list
> Linux-nvdimm@...ts.01.org
> https://lists.01.org/mailman/listinfo/linux-nvdimm
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