diff options
Diffstat (limited to 'drivers/staging/android/ashmem.c')
-rw-r--r-- | drivers/staging/android/ashmem.c | 40 |
1 files changed, 40 insertions, 0 deletions
diff --git a/drivers/staging/android/ashmem.c b/drivers/staging/android/ashmem.c index 74d497d39c5a..19b0cc5ea33f 100644 --- a/drivers/staging/android/ashmem.c +++ b/drivers/staging/android/ashmem.c @@ -95,6 +95,15 @@ static DEFINE_MUTEX(ashmem_mutex); static struct kmem_cache *ashmem_area_cachep __read_mostly; static struct kmem_cache *ashmem_range_cachep __read_mostly; +/* + * A separate lockdep class for the backing shmem inodes to resolve the lockdep + * warning about the race between kswapd taking fs_reclaim before inode_lock + * and write syscall taking inode_lock and then fs_reclaim. + * Note that such race is impossible because ashmem does not support write + * syscalls operating on the backing shmem. + */ +static struct lock_class_key backing_shmem_inode_class; + static inline unsigned long range_size(struct ashmem_range *range) { return range->pgend - range->pgstart + 1; @@ -351,8 +360,23 @@ static inline vm_flags_t calc_vm_may_flags(unsigned long prot) _calc_vm_trans(prot, PROT_EXEC, VM_MAYEXEC); } +static int ashmem_vmfile_mmap(struct file *file, struct vm_area_struct *vma) +{ + /* do not allow to mmap ashmem backing shmem file directly */ + return -EPERM; +} + +static unsigned long +ashmem_vmfile_get_unmapped_area(struct file *file, unsigned long addr, + unsigned long len, unsigned long pgoff, + unsigned long flags) +{ + return current->mm->get_unmapped_area(file, addr, len, pgoff, flags); +} + static int ashmem_mmap(struct file *file, struct vm_area_struct *vma) { + static struct file_operations vmfile_fops; struct ashmem_area *asma = file->private_data; int ret = 0; @@ -381,6 +405,7 @@ static int ashmem_mmap(struct file *file, struct vm_area_struct *vma) if (!asma->file) { char *name = ASHMEM_NAME_DEF; struct file *vmfile; + struct inode *inode; if (asma->name[ASHMEM_NAME_PREFIX_LEN] != '\0') name = asma->name; @@ -392,7 +417,22 @@ static int ashmem_mmap(struct file *file, struct vm_area_struct *vma) goto out; } vmfile->f_mode |= FMODE_LSEEK; + inode = file_inode(vmfile); + lockdep_set_class(&inode->i_rwsem, &backing_shmem_inode_class); asma->file = vmfile; + /* + * override mmap operation of the vmfile so that it can't be + * remapped which would lead to creation of a new vma with no + * asma permission checks. Have to override get_unmapped_area + * as well to prevent VM_BUG_ON check for f_ops modification. + */ + if (!vmfile_fops.mmap) { + vmfile_fops = *vmfile->f_op; + vmfile_fops.mmap = ashmem_vmfile_mmap; + vmfile_fops.get_unmapped_area = + ashmem_vmfile_get_unmapped_area; + } + vmfile->f_op = &vmfile_fops; } get_file(asma->file); |