f2fs: fix to avoid mmap vs set_compress_option case

Compression option in inode should not be changed after they have
been used, however, it may happen in below race case:

Thread A				Thread B
- f2fs_ioc_set_compress_option
 - check f2fs_is_mmap_file()
 - check get_dirty_pages()
 - check F2FS_HAS_BLOCKS()
					- f2fs_file_mmap
					 - set_inode_flag(FI_MMAP_FILE)
					- fault
					 - do_page_mkwrite
					  - f2fs_vm_page_mkwrite
					  - f2fs_get_block_locked
					 - fault_dirty_shared_page
					  - set_page_dirty
 - update i_compress_algorithm
 - update i_log_cluster_size
 - update i_cluster_size

Avoid such race condition by covering f2fs_file_mmap() w/ i_sem lock,
meanwhile add mmap file check condition in f2fs_may_compress() as well.

Fixes: e1e8debec656 ("f2fs: add F2FS_IOC_SET_COMPRESS_OPTION ioctl")
Signed-off-by: Chao Yu <chao@kernel.org>
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>

diff --git a/fs/f2fs/f2fs.h b/fs/f2fs/f2fs.h
index c7cb2177b25273e1af35b4d28a1504d7eaa0e3d0..d372bedb0fe4e1accb56e4761f814a9ee08d0990 100644 (file)
--- a/fs/f2fs/f2fs.h
+++ b/fs/f2fs/f2fs.h
@@ -4483,7 +4483,8 @@ static inline bool f2fs_low_mem_mode(struct f2fs_sb_info *sbi)
 static inline bool f2fs_may_compress(struct inode *inode)
 {
        if (IS_SWAPFILE(inode) || f2fs_is_pinned_file(inode) ||
-               f2fs_is_atomic_file(inode) || f2fs_has_inline_data(inode))
+               f2fs_is_atomic_file(inode) || f2fs_has_inline_data(inode) ||
+               f2fs_is_mmap_file(inode))
                return false;
        return S_ISREG(inode->i_mode) || S_ISDIR(inode->i_mode);
 }

diff --git a/fs/f2fs/file.c b/fs/f2fs/file.c
index 093039dee99206715c9b878838cdcfdc7a4b289e..d9073afe021fd43a39507ada34638acee66970a1 100644 (file)
--- a/fs/f2fs/file.c
+++ b/fs/f2fs/file.c
@@ -526,7 +526,11 @@ static int f2fs_file_mmap(struct file *file, struct vm_area_struct *vma)
 
        file_accessed(file);
        vma->vm_ops = &f2fs_file_vm_ops;
+
+       f2fs_down_read(&F2FS_I(inode)->i_sem);
        set_inode_flag(inode, FI_MMAP_FILE);
+       f2fs_up_read(&F2FS_I(inode)->i_sem);
+
        return 0;
 }
 
@@ -1919,12 +1923,19 @@ static int f2fs_setflags_common(struct inode *inode, u32 iflags, u32 mask)
                        int err = f2fs_convert_inline_inode(inode);
                        if (err)
                                return err;
-                       if (!f2fs_may_compress(inode))
-                               return -EINVAL;
-                       if (S_ISREG(inode->i_mode) && F2FS_HAS_BLOCKS(inode))
+
+                       f2fs_down_write(&F2FS_I(inode)->i_sem);
+                       if (!f2fs_may_compress(inode) ||
+                                       (S_ISREG(inode->i_mode) &&
+                                       F2FS_HAS_BLOCKS(inode))) {
+                               f2fs_up_write(&F2FS_I(inode)->i_sem);
                                return -EINVAL;
-                       if (set_compress_context(inode))
-                               return -EOPNOTSUPP;
+                       }
+                       err = set_compress_context(inode);
+                       f2fs_up_write(&F2FS_I(inode)->i_sem);
+
+                       if (err)
+                               return err;
                }
        }
 
@@ -3976,6 +3987,7 @@ static int f2fs_ioc_set_compress_option(struct file *filp, unsigned long arg)
        file_start_write(filp);
        inode_lock(inode);
 
+       f2fs_down_write(&F2FS_I(inode)->i_sem);
        if (f2fs_is_mmap_file(inode) || get_dirty_pages(inode)) {
                ret = -EBUSY;
                goto out;
@@ -3995,6 +4007,7 @@ static int f2fs_ioc_set_compress_option(struct file *filp, unsigned long arg)
                f2fs_warn(sbi, "compression algorithm is successfully set, "
                        "but current kernel doesn't support this algorithm.");
 out:
+       f2fs_up_write(&F2FS_I(inode)->i_sem);
        inode_unlock(inode);
        file_end_write(filp);