From: Jeff Xu <jeffxu@xxxxxxxxxxxx> Seal vdso, vvar, sigpage, uprobes and vsyscall. Those mappings are readonly or executable only, sealing can protect them from ever changing during the life time of the process. For complete descriptions of memory sealing, please see mseal.rst [1]. System mappings such as vdso, vvar, and sigpage (for arm) are generated by the kernel during program initialization. These mappings are designated as non-writable, and sealing them will prevent them from ever becoming writeable. Unlike the aforementioned mappings, the uprobe mapping is not established during program startup. However, its lifetime is the same as the process's lifetime [2], thus sealable. The vdso, vvar, sigpage, and uprobe mappings all invoke the _install_special_mapping() function. As no other mappings utilize this function, it is logical to incorporate sealing logic within _install_special_mapping(). This approach avoids the necessity of modifying code across various architecture-specific implementations. The vsyscall mapping, which has its own initialization function, is sealed in the XONLY case, it seems to be the most common and secure case of using vsyscall. It is important to note that the CHECKPOINT_RESTORE feature (CRIU) may alter the mapping of vdso, vvar, and sigpage during restore operations. Consequently, this feature cannot be universally enabled across all systems. To address this, a kernel configuration option has been introduced to enable or disable this functionality. Note, uprobe is always sealed and not controlled by this kernel configuration. I tested CONFIG_SEAL_SYSTEM_MAPPINGS_ALWAYS with ChromeOS, which doesn’t use CHECKPOINT_RESTORE. [1] Documentation/userspace-api/mseal.rst [2] https://lore.kernel.org/all/CABi2SkU9BRUnqf70-nksuMCQ+yyiWjo3fM4XkRkL-NrCZxYAyg@xxxxxxxxxxxxxx/ History: V2: Seal uprobe always (Oleg Nesterov) Update comments and description (Randy Dunlap, Liam R.Howlett, Oleg Nesterov) Rebase to linux_main V1: https://lore.kernel.org/all/20241004163155.3493183-1-jeffxu@xxxxxxxxxx/ Jeff Xu (1): exec: seal system mappings .../admin-guide/kernel-parameters.txt | 10 ++++ arch/x86/entry/vsyscall/vsyscall_64.c | 9 +++- fs/exec.c | 53 +++++++++++++++++++ include/linux/fs.h | 1 + kernel/events/uprobes.c | 2 +- mm/mmap.c | 1 + security/Kconfig | 26 +++++++++ 7 files changed, 99 insertions(+), 3 deletions(-) -- 2.47.0.rc1.288.g06298d1525-goog
