diff options
Diffstat (limited to 'arch/um/kernel/skas/mmu.c')
| -rw-r--r-- | arch/um/kernel/skas/mmu.c | 24 |
1 files changed, 24 insertions, 0 deletions
diff --git a/arch/um/kernel/skas/mmu.c b/arch/um/kernel/skas/mmu.c index 697dad49c36b..47f98d87ea3c 100644 --- a/arch/um/kernel/skas/mmu.c +++ b/arch/um/kernel/skas/mmu.c @@ -40,6 +40,30 @@ int init_new_context(struct task_struct *task, struct mm_struct *mm) goto out_free; } + /* + * Ensure the new MM is clean and nothing unwanted is mapped. + * + * TODO: We should clear the memory up to STUB_START to ensure there is + * nothing mapped there, i.e. we (currently) have: + * + * |- user memory -|- unused -|- stub -|- unused -| + * ^ TASK_SIZE ^ STUB_START + * + * Meaning we have two unused areas where we may still have valid + * mappings from our internal clone(). That isn't really a problem as + * userspace is not going to access them, but it is definitely not + * correct. + * + * However, we are "lucky" and if rseq is configured, then on 32 bit + * it will fall into the first empty range while on 64 bit it is going + * to use an anonymous mapping in the second range. As such, things + * continue to work for now as long as we don't start unmapping these + * areas. + * + * Change this to STUB_START once we have a clean userspace. + */ + unmap(new_id, 0, TASK_SIZE); + return 0; out_free: |