On 09.07.24 15:20, Patrick Roy wrote:
Inside of vma_is_secretmem and secretmem_mapping, instead of checking whether a vm_area_struct/address_space has the secretmem ops structure attached to it, check whether the address_space has the AS_INACCESSIBLE bit set. Then set the AS_INACCESSIBLE flag for secretmem's address_space. This means that get_user_pages and friends are disables for all adress_spaces that set AS_INACCESIBLE. The AS_INACCESSIBLE flag was introduced in commit c72ceafbd12c ("mm: Introduce AS_INACCESSIBLE for encrypted/confidential memory") specifically for guest_memfd to indicate that no reads and writes should ever be done to guest_memfd address_spaces. Disallowing gup seems like a reasonable semantic extension, and means that potential future mmaps of guest_memfd cannot be GUP'd. Signed-off-by: Patrick Roy <roypat@xxxxxxxxxxxx> --- include/linux/secretmem.h | 13 +++++++++++-- mm/secretmem.c | 6 +----- 2 files changed, 12 insertions(+), 7 deletions(-) diff --git a/include/linux/secretmem.h b/include/linux/secretmem.h index e918f96881f5..886c8f7eb63e 100644 --- a/include/linux/secretmem.h +++ b/include/linux/secretmem.h @@ -8,10 +8,19 @@ extern const struct address_space_operations secretmem_aops;static inline bool secretmem_mapping(struct address_space *mapping){ - return mapping->a_ops == &secretmem_aops; + return mapping->flags & AS_INACCESSIBLE; +} + +static inline bool vma_is_secretmem(struct vm_area_struct *vma) +{ + struct file *file = vma->vm_file; + + if (!file) + return false; + + return secretmem_mapping(file->f_inode->i_mapping); }
That sounds wrong. You should leave *secretmem alone and instead have something like inaccessible_mapping that is used where appropriate.
vma_is_secretmem() should not suddenly succeed on something that is not mm/secretmem.c
-- Cheers, David / dhildenb
