diff options
Diffstat (limited to 'mm/memfd.c')
| -rw-r--r-- | mm/memfd.c | 44 |
1 files changed, 43 insertions, 1 deletions
diff --git a/mm/memfd.c b/mm/memfd.c index 35a370d75c9a..5f5a23c9051d 100644 --- a/mm/memfd.c +++ b/mm/memfd.c @@ -170,7 +170,7 @@ static int memfd_wait_for_pins(struct address_space *mapping) return error; } -unsigned int *memfd_file_seals_ptr(struct file *file) +static unsigned int *memfd_file_seals_ptr(struct file *file) { if (shmem_file(file)) return &SHMEM_I(file_inode(file))->seals; @@ -327,6 +327,48 @@ static int check_sysctl_memfd_noexec(unsigned int *flags) return 0; } +static inline bool is_write_sealed(unsigned int seals) +{ + return seals & (F_SEAL_WRITE | F_SEAL_FUTURE_WRITE); +} + +static int check_write_seal(unsigned long *vm_flags_ptr) +{ + unsigned long vm_flags = *vm_flags_ptr; + unsigned long mask = vm_flags & (VM_SHARED | VM_WRITE); + + /* If a private matting then writability is irrelevant. */ + if (!(mask & VM_SHARED)) + return 0; + + /* + * New PROT_WRITE and MAP_SHARED mmaps are not allowed when + * write seals are active. + */ + if (mask & VM_WRITE) + return -EPERM; + + /* + * This is a read-only mapping, disallow mprotect() from making a + * write-sealed mapping writable in future. + */ + *vm_flags_ptr &= ~VM_MAYWRITE; + + return 0; +} + +int memfd_check_seals_mmap(struct file *file, unsigned long *vm_flags_ptr) +{ + int err = 0; + unsigned int *seals_ptr = memfd_file_seals_ptr(file); + unsigned int seals = seals_ptr ? *seals_ptr : 0; + + if (is_write_sealed(seals)) + err = check_write_seal(vm_flags_ptr); + + return err; +} + SYSCALL_DEFINE2(memfd_create, const char __user *, uname, unsigned int, flags) |