The driver exposes EFI runtime services to user-space through an IOCTL interface, calling the EFI services function pointers directly without using the efivar API. Disallow access to the /dev/efi_test character device when the kernel is locked down to prevent arbitrary user-space to call EFI runtime services. Also require CAP_SYS_ADMIN to open the chardev to prevent unprivileged users to call the EFI runtime services, instead of just relying on the chardev file mode bits for this. The main user of this driver is the fwts [0] tool that already checks if the effective user ID is 0 and fails otherwise. So this change shouldn't cause any regression to this tool. [0]: https://wiki.ubuntu.com/FirmwareTestSuite/Reference/uefivarinfo
Unified · Split
| @@ -14,6 +14,7 @@ · 13 unmodified lines | ||
| 14 | 14 | #include <linux/init.h> |
| 15 | 15 | #include <linux/proc_fs.h> |
| 16 | 16 | #include <linux/efi.h> |
| 17 | +#include <linux/security.h> | |
| 17 | 18 | #include <linux/slab.h> |
| 18 | 19 | #include <linux/uaccess.h> |
| 19 | 20 | |
| @@ -717,6 +718,13 @@ static long efi_test_ioctl(struct file *file, unsigned int cmd, · 697 unmodified lines | ||
| 717 | 718 | |
| 718 | 719 | static int efi_test_open(struct inode *inode, struct file *file) |
| 719 | 720 | { |
| 721 | + int ret = security_locked_down(LOCKDOWN_EFI_TEST); | |
| 722 | + | |
| 723 | + if (ret) | |
| 724 | + return ret; | |
| 725 | + | |
| 726 | + if (!capable(CAP_SYS_ADMIN)) | |
| 727 | + return -EACCES; | |
| 720 | 728 | /* |
| 721 | 729 | * nothing special to do here |
| 722 | 730 | * We do accept multiple open files at the same time as we |
| @@ -105,6 +105,7 @@ enum lockdown_reason { · 104 unmodified lines | ||
| 105 | 105 | LOCKDOWN_NONE, |
| 106 | 106 | LOCKDOWN_MODULE_SIGNATURE, |
| 107 | 107 | LOCKDOWN_DEV_MEM, |
| 108 | + LOCKDOWN_EFI_TEST, | |
| 108 | 109 | LOCKDOWN_KEXEC, |
| 109 | 110 | LOCKDOWN_HIBERNATION, |
| 110 | 111 | LOCKDOWN_PCI_ACCESS, |
| @@ -20,6 +20,7 @@ static const char *const lockdown_reasons[LOCKDOWN_CONFIDENTIALITY_MAX+1] = { · 19 unmodified lines | ||
| 20 | 20 | [LOCKDOWN_NONE] = "none", |
| 21 | 21 | [LOCKDOWN_MODULE_SIGNATURE] = "unsigned module loading", |
| 22 | 22 | [LOCKDOWN_DEV_MEM] = "/dev/mem,kmem,port", |
| 23 | + [LOCKDOWN_EFI_TEST] = "/dev/efi_test access", | |
| 23 | 24 | [LOCKDOWN_KEXEC] = "kexec of unsigned images", |
| 24 | 25 | [LOCKDOWN_HIBERNATION] = "hibernation", |
| 25 | 26 | [LOCKDOWN_PCI_ACCESS] = "direct PCI access", |