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PCI/switchtec: Add Gen4 MRPC GAS access permission check

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Gen4 hardware provides new MRPC commands to read and write directly from
any address in the PCI BAR (which Microsemi refers to as GAS). Since
accessing BARs can be dangerous and break the driver, we don't want
unprivileged users to have this ability.

Therefore, require CAP_SYS_ADMIN for the local and remote GAS access MRPC
commands. Privileged processes will already have access to the BAR through
the sysfs resource file so this doesn't give userspace any capabilities it
didn't already have.

[logang@deltatee.com: rework commit message]
Link: https://lore.kernel.org/r/20200106190337.2428-11-logang@deltatee.com
Signed-off-by: Kelvin Cao <kelvin.cao@microchip.com>
Signed-off-by: Logan Gunthorpe <logang@deltatee.com>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
This commit is contained in:
Kelvin Cao
2020-01-06 12:03:35 -07:00
committed by Bjorn Helgaas
parent 4efa1d2e36
commit ce7c88600b
2 changed files with 11 additions and 0 deletions
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6
drivers/pci/switch/switchtec.c
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@@ -479,6 +479,12 @@ static ssize_t switchtec_dev_write(struct file *filp, const char __user *data,
rc = -EFAULT;
goto out;
}
if (((MRPC_CMD_ID(stuser->cmd) == MRPC_GAS_WRITE) ||
(MRPC_CMD_ID(stuser->cmd) == MRPC_GAS_READ)) &&
!capable(CAP_SYS_ADMIN)) {
rc = -EPERM;
goto out;
}
data += sizeof(stuser->cmd);
rc = copy_from_user(&stuser->data, data, size - sizeof(stuser->cmd));