6.15-stable review patch. If anyone has any objections, please let me know.
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From: Dan Williams dan.j.williams@intel.com
commit fba4ceaa242d2bdf4c04b77bda41d32d02d3925d upstream.
Unlike sysfs, the lifetime of configfs objects is controlled by userspace. There is no mechanism for the kernel to find and delete all created config-items. Instead, the configfs-tsm-report mechanism has an expectation that tsm_unregister() can happen at any time and cause established config-item access to start failing.
That expectation is not fully satisfied. While tsm_report_read(), tsm_report_{is,is_bin}_visible(), and tsm_report_make_item() safely fail if tsm_ops have been unregistered, tsm_report_privlevel_store() tsm_report_provider_show() fail to check for ops registration. Add the missing checks for tsm_ops having been removed.
Now, in supporting the ability for tsm_unregister() to always succeed, it leaves the problem of what to do with lingering config-items. The expectation is that the admin that arranges for the ->remove() (unbind) of the ${tsm_arch}-guest driver is also responsible for deletion of all open config-items. Until that deletion happens, ->probe() (reload / bind) of the ${tsm_arch}-guest driver fails.
This allows for emergency shutdown / revocation of attestation interfaces, and requires coordinated restart.
Fixes: 70e6f7e2b985 ("configfs-tsm: Introduce a shared ABI for attestation reports") Cc: stable@vger.kernel.org Cc: Suzuki K Poulose suzuki.poulose@arm.com Cc: Steven Price steven.price@arm.com Cc: Sami Mujawar sami.mujawar@arm.com Cc: Borislav Petkov (AMD) bp@alien8.de Cc: Tom Lendacky thomas.lendacky@amd.com Reviewed-by: Kuppuswamy Sathyanarayanan sathyanarayanan.kuppuswamy@linux.intel.com Reported-by: Cedric Xing cedric.xing@intel.com Reviewed-by: Kai Huang kai.huang@intel.com Link: https://patch.msgid.link/20250430203331.1177062-1-dan.j.williams@intel.com Signed-off-by: Dan Williams dan.j.williams@intel.com Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- drivers/virt/coco/tsm.c | 31 +++++++++++++++++++++++++++++-- 1 file changed, 29 insertions(+), 2 deletions(-)
--- a/drivers/virt/coco/tsm.c +++ b/drivers/virt/coco/tsm.c @@ -15,6 +15,7 @@ static struct tsm_provider { const struct tsm_ops *ops; void *data; + atomic_t count; } provider; static DECLARE_RWSEM(tsm_rwsem);
@@ -92,6 +93,10 @@ static ssize_t tsm_report_privlevel_stor if (rc) return rc;
+ guard(rwsem_write)(&tsm_rwsem); + if (!provider.ops) + return -ENXIO; + /* * The valid privilege levels that a TSM might accept, if it accepts a * privilege level setting at all, are a max of TSM_PRIVLEVEL_MAX (see @@ -101,7 +106,6 @@ static ssize_t tsm_report_privlevel_stor if (provider.ops->privlevel_floor > val || val > TSM_PRIVLEVEL_MAX) return -EINVAL;
- guard(rwsem_write)(&tsm_rwsem); rc = try_advance_write_generation(report); if (rc) return rc; @@ -115,6 +119,10 @@ static ssize_t tsm_report_privlevel_floo char *buf) { guard(rwsem_read)(&tsm_rwsem); + + if (!provider.ops) + return -ENXIO; + return sysfs_emit(buf, "%u\n", provider.ops->privlevel_floor); } CONFIGFS_ATTR_RO(tsm_report_, privlevel_floor); @@ -217,6 +225,9 @@ CONFIGFS_ATTR_RO(tsm_report_, generation static ssize_t tsm_report_provider_show(struct config_item *cfg, char *buf) { guard(rwsem_read)(&tsm_rwsem); + if (!provider.ops) + return -ENXIO; + return sysfs_emit(buf, "%s\n", provider.ops->name); } CONFIGFS_ATTR_RO(tsm_report_, provider); @@ -284,7 +295,7 @@ static ssize_t tsm_report_read(struct ts guard(rwsem_write)(&tsm_rwsem); ops = provider.ops; if (!ops) - return -ENOTTY; + return -ENXIO; if (!report->desc.inblob_len) return -EINVAL;
@@ -421,12 +432,20 @@ static struct config_item *tsm_report_ma if (!state) return ERR_PTR(-ENOMEM);
+ atomic_inc(&provider.count); config_item_init_type_name(&state->cfg, name, &tsm_report_type); return &state->cfg; }
+static void tsm_report_drop_item(struct config_group *group, struct config_item *item) +{ + config_item_put(item); + atomic_dec(&provider.count); +} + static struct configfs_group_operations tsm_report_group_ops = { .make_item = tsm_report_make_item, + .drop_item = tsm_report_drop_item, };
static const struct config_item_type tsm_reports_type = { @@ -459,6 +478,11 @@ int tsm_register(const struct tsm_ops *o return -EBUSY; }
+ if (atomic_read(&provider.count)) { + pr_err("configfs/tsm/report not empty\n"); + return -EBUSY; + } + provider.ops = ops; provider.data = priv; return 0; @@ -470,6 +494,9 @@ int tsm_unregister(const struct tsm_ops guard(rwsem_write)(&tsm_rwsem); if (ops != provider.ops) return -EBUSY; + if (atomic_read(&provider.count)) + pr_warn(""%s" unregistered with items present in configfs/tsm/report\n", + provider.ops->name); provider.ops = NULL; provider.data = NULL; return 0;