diff options
| -rw-r--r-- | include/linux/fs.h | 6 | ||||
| -rw-r--r-- | mm/util.c | 40 | ||||
| -rw-r--r-- | mm/vma.c | 1 | ||||
| -rw-r--r-- | mm/vma.h | 47 | ||||
| -rw-r--r-- | tools/testing/vma/vma_internal.h | 16 |
5 files changed, 107 insertions, 3 deletions
diff --git a/include/linux/fs.h b/include/linux/fs.h index 96c7925a6551..4ec77da65f14 100644 --- a/include/linux/fs.h +++ b/include/linux/fs.h @@ -2274,10 +2274,12 @@ static inline bool file_has_valid_mmap_hooks(struct file *file) return true; } +int compat_vma_mmap_prepare(struct file *file, struct vm_area_struct *vma); + static inline int call_mmap(struct file *file, struct vm_area_struct *vma) { - if (WARN_ON_ONCE(file->f_op->mmap_prepare)) - return -EINVAL; + if (file->f_op->mmap_prepare) + return compat_vma_mmap_prepare(file, vma); return file->f_op->mmap(file, vma); } diff --git a/mm/util.c b/mm/util.c index 448117da071f..0b270c43d7d1 100644 --- a/mm/util.c +++ b/mm/util.c @@ -1131,3 +1131,43 @@ void flush_dcache_folio(struct folio *folio) } EXPORT_SYMBOL(flush_dcache_folio); #endif + +/** + * compat_vma_mmap_prepare() - Apply the file's .mmap_prepare() hook to an + * existing VMA + * @file: The file which possesss an f_op->mmap_prepare() hook + * @vma: The VMA to apply the .mmap_prepare() hook to. + * + * Ordinarily, .mmap_prepare() is invoked directly upon mmap(). However, certain + * 'wrapper' file systems invoke a nested mmap hook of an underlying file. + * + * Until all filesystems are converted to use .mmap_prepare(), we must be + * conservative and continue to invoke these 'wrapper' filesystems using the + * deprecated .mmap() hook. + * + * However we have a problem if the underlying file system possesses an + * .mmap_prepare() hook, as we are in a different context when we invoke the + * .mmap() hook, already having a VMA to deal with. + * + * compat_vma_mmap_prepare() is a compatibility function that takes VMA state, + * establishes a struct vm_area_desc descriptor, passes to the underlying + * .mmap_prepare() hook and applies any changes performed by it. + * + * Once the conversion of filesystems is complete this function will no longer + * be required and will be removed. + * + * Returns: 0 on success or error. + */ +int compat_vma_mmap_prepare(struct file *file, struct vm_area_struct *vma) +{ + struct vm_area_desc desc; + int err; + + err = file->f_op->mmap_prepare(vma_to_desc(vma, &desc)); + if (err) + return err; + set_vma_from_desc(vma, &desc); + + return 0; +} +EXPORT_SYMBOL(compat_vma_mmap_prepare); @@ -3113,7 +3113,6 @@ int __vm_munmap(unsigned long start, size_t len, bool unlock) return ret; } - /* Insert vm structure into process list sorted by address * and into the inode's i_mmap tree. If vm_file is non-NULL * then i_mmap_rwsem is taken here. @@ -222,6 +222,53 @@ static inline int vma_iter_store_gfp(struct vma_iterator *vmi, return 0; } + +/* + * Temporary helper functions for file systems which wrap an invocation of + * f_op->mmap() but which might have an underlying file system which implements + * f_op->mmap_prepare(). + */ + +static inline struct vm_area_desc *vma_to_desc(struct vm_area_struct *vma, + struct vm_area_desc *desc) +{ + desc->mm = vma->vm_mm; + desc->start = vma->vm_start; + desc->end = vma->vm_end; + + desc->pgoff = vma->vm_pgoff; + desc->file = vma->vm_file; + desc->vm_flags = vma->vm_flags; + desc->page_prot = vma->vm_page_prot; + + desc->vm_ops = NULL; + desc->private_data = NULL; + + return desc; +} + +static inline void set_vma_from_desc(struct vm_area_struct *vma, + struct vm_area_desc *desc) +{ + /* + * Since we're invoking .mmap_prepare() despite having a partially + * established VMA, we must take care to handle setting fields + * correctly. + */ + + /* Mutable fields. Populated with initial state. */ + vma->vm_pgoff = desc->pgoff; + if (vma->vm_file != desc->file) + vma_set_file(vma, desc->file); + if (vma->vm_flags != desc->vm_flags) + vm_flags_set(vma, desc->vm_flags); + vma->vm_page_prot = desc->page_prot; + + /* User-defined fields. */ + vma->vm_ops = desc->vm_ops; + vma->vm_private_data = desc->private_data; +} + int do_vmi_align_munmap(struct vma_iterator *vmi, struct vm_area_struct *vma, struct mm_struct *mm, unsigned long start, diff --git a/tools/testing/vma/vma_internal.h b/tools/testing/vma/vma_internal.h index 4505b1c31be1..14718ca23a05 100644 --- a/tools/testing/vma/vma_internal.h +++ b/tools/testing/vma/vma_internal.h @@ -159,6 +159,14 @@ typedef __bitwise unsigned int vm_fault_t; #define ASSERT_EXCLUSIVE_WRITER(x) +/** + * swap - swap values of @a and @b + * @a: first value + * @b: second value + */ +#define swap(a, b) \ + do { typeof(a) __tmp = (a); (a) = (b); (b) = __tmp; } while (0) + struct kref { refcount_t refcount; }; @@ -1468,4 +1476,12 @@ static inline void fixup_hugetlb_reservations(struct vm_area_struct *vma) (void)vma; } +static inline void vma_set_file(struct vm_area_struct *vma, struct file *file) +{ + /* Changing an anonymous vma with this is illegal */ + get_file(file); + swap(vma->vm_file, file); + fput(file); +} + #endif /* __MM_VMA_INTERNAL_H */ |