Hi,
Static analysis on linux-next detected a potential uninitialized
variable dn.node_changed that does not get set when a call to
f2fs_get_node_page() fails. This uninitialized value gets used in the
call to f2fs_balance_fs() that may or not may not balances dirty node
and dentry pages depending on the uninitialized state of the variable.
I believe the issue was introduced by commit:
commit 2a3407607028f7c780f1c20faa4e922bf631d340
Author: Jaegeuk Kim <jaeg...@kernel.org>
Date: Tue Dec 22 13:23:35 2015 -0800
f2fs: call f2fs_balance_fs only when node was changed
The analysis is a follows:
184 int f2fs_convert_inline_inode(struct inode *inode)
185 {
186 struct f2fs_sb_info *sbi = F2FS_I_SB(inode);
1. var_decl: Declaring variable dn without initializer.
187 struct dnode_of_data dn;
NOTE dn is not initialized here.
188 struct page *ipage, *page;
189 int err = 0;
190
2. Condition !f2fs_has_inline_data(inode), taking false branch.
3. Condition f2fs_hw_is_readonly(sbi), taking false branch.
4. Condition f2fs_readonly(sbi->sb), taking false branch.
191 if (!f2fs_has_inline_data(inode) ||
192 f2fs_hw_is_readonly(sbi) ||
f2fs_readonly(sbi->sb))
193 return 0;
194
195 err = dquot_initialize(inode);
5. Condition err, taking false branch.
196 if (err)
197 return err;
198
199 page = f2fs_grab_cache_page(inode->i_mapping, 0, false);
6. Condition !page, taking false branch.
200 if (!page)
201 return -ENOMEM;
202
203 f2fs_lock_op(sbi);
204
205 ipage = f2fs_get_node_page(sbi, inode->i_ino);
7. Condition IS_ERR(ipage), taking true branch.
206 if (IS_ERR(ipage)) {
207 err = PTR_ERR(ipage);
8. Jumping to label out.
208 goto out;
209 }
210
NOTE: set_new_dnode memset's dn so sets the flag to false, but we
don't get to this memset if IS_ERR(ipage) above is true.
211 set_new_dnode(&dn, inode, ipage, ipage, 0);
212
213 if (f2fs_has_inline_data(inode))
214 err = f2fs_convert_inline_page(&dn, page);
215
216 f2fs_put_dnode(&dn);
217 out:
218 f2fs_unlock_op(sbi);
219
220 f2fs_put_page(page, 1);
221
Uninitialized scalar variable:
9. uninit_use_in_call: Using uninitialized value dn.node_changed when
calling f2fs_balance_fs.
222 f2fs_balance_fs(sbi, dn.node_changed);
223
224 return err;
225 }
I think a suitable fix will be to set dn.node_changed to false on in
line 207-208 but I'm concerned if I'm missing something subtle to the
rebalancing if I do this.
Comments?
Colin
