[Feature]: Provide SEV_FEATURES and VINTR_CTRL from user space to stabilize attestation #8
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dpal
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In the error path in ata_tport_add(), when calling put_device(), ata_tport_release() is called, it will put the refcount of 'ap->host'. And then ata_host_put() is called again, the refcount is decreased to 0, ata_host_release() is called, all ports are freed and set to null. When unbinding the device after failure, ata_host_stop() is called to release the resources, it leads a null-ptr-deref(), because all the ports all freed and null. Unable to handle kernel NULL pointer dereference at virtual address 0000000000000008 CPU: 7 PID: 18671 Comm: modprobe Kdump: loaded Tainted: G E 6.1.0-rc3+ enarx#8 pstate: 80400009 (Nzcv daif +PAN -UAO -TCO -DIT -SSBS BTYPE=--) pc : ata_host_stop+0x3c/0x84 [libata] lr : release_nodes+0x64/0xd0 Call trace: ata_host_stop+0x3c/0x84 [libata] release_nodes+0x64/0xd0 devres_release_all+0xbc/0x1b0 device_unbind_cleanup+0x20/0x70 really_probe+0x158/0x320 __driver_probe_device+0x84/0x120 driver_probe_device+0x44/0x120 __driver_attach+0xb4/0x220 bus_for_each_dev+0x78/0xdc driver_attach+0x2c/0x40 bus_add_driver+0x184/0x240 driver_register+0x80/0x13c __pci_register_driver+0x4c/0x60 ahci_pci_driver_init+0x30/0x1000 [ahci] Fix this by removing redundant ata_host_put() in the error path. Fixes: 2623c7a ("libata: add refcounting to ata_host") Signed-off-by: Yang Yingliang <[email protected]> Signed-off-by: Damien Le Moal <[email protected]>
dpal
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Jan 27, 2023
In ata_tport_add(), the return value of transport_add_device() is not checked. As a result, it causes null-ptr-deref while removing the module, because transport_remove_device() is called to remove the device that was not added. Unable to handle kernel NULL pointer dereference at virtual address 00000000000000d0 CPU: 12 PID: 13605 Comm: rmmod Kdump: loaded Tainted: G W 6.1.0-rc3+ enarx#8 pstate: 60400009 (nZCv daif +PAN -UAO -TCO -DIT -SSBS BTYPE=--) pc : device_del+0x48/0x39c lr : device_del+0x44/0x39c Call trace: device_del+0x48/0x39c attribute_container_class_device_del+0x28/0x40 transport_remove_classdev+0x60/0x7c attribute_container_device_trigger+0x118/0x120 transport_remove_device+0x20/0x30 ata_tport_delete+0x34/0x60 [libata] ata_port_detach+0x148/0x1b0 [libata] ata_pci_remove_one+0x50/0x80 [libata] ahci_remove_one+0x4c/0x8c [ahci] Fix this by checking and handling return value of transport_add_device() in ata_tport_add(). Fixes: d902747 ("[libata] Add ATA transport class") Signed-off-by: Yang Yingliang <[email protected]> Signed-off-by: Damien Le Moal <[email protected]>
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Description
SEV_FEATURES and VINTR_CTRL change in Linux can break any program using SEV-SNP attestation, as the digest calculation might rely on older values. This could cause old binaries break on new kernel versions without warning.
Something like LAUNCH_UPDATE_VMSA_RESET_VECTOR command with SEV_FEATURES and VINTR_CTRL as parameters would work out, which would partially overwrite kernel VMSA.
Potentially they could be capped by kernel, i.e. "further restrict what kernel allows" should work out.
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Suggestions for a technical implementation
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