f2fs_convert_inline_inode causing rebalance based on random uninitialized value in dn.node_changed

f2fs_convert_inline_inode causing rebalance based on random uninitialized value in dn.node_changed

[Colin Ian King]

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 <jaegeuk@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

Re: f2fs_convert_inline_inode causing rebalance based on random uninitialized value in dn.node_changed

[Jaegeuk Kim]

On 03/02, Colin Ian King wrote:
> 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 <jaegeuk@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?

Thank you for the report. Yes, it seems that's a right call and we need to
check the error to decide calling f2fs_balance_fs() in line 222, since
set_new_dnode() is used to set all the fields in dnode_of_data. So, if you
don't mind, could you please post a patch?

Thanks,

> 
> Colin
> 

Re: f2fs_convert_inline_inode causing rebalance based on random uninitialized value in dn.node_changed

[Colin Ian King]

On 03/03/2021 19:44, Jaegeuk Kim wrote:
> On 03/02, Colin Ian King wrote:
>> 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 <jaegeuk@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?
> 
> Thank you for the report. Yes, it seems that's a right call and we need to
> check the error to decide calling f2fs_balance_fs() in line 222, since
> set_new_dnode() is used to set all the fields in dnode_of_data. So, if you
> don't mind, could you please post a patch?

Just to clarify, just setting dn.node_changes to false is enough?

I'm not entirely sure what you meant when you wrote "and we need to
check the error to decide calling f2fs_balance_fs() in line 222".

Colin

> 
> Thanks,
> 
>>
>> Colin
>>

Re: f2fs_convert_inline_inode causing rebalance based on random uninitialized value in dn.node_changed

[Jaegeuk Kim]

On 03/03, Colin Ian King wrote:
> On 03/03/2021 19:44, Jaegeuk Kim wrote:
> > On 03/02, Colin Ian King wrote:
> >> 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 <jaegeuk@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?
> > 
> > Thank you for the report. Yes, it seems that's a right call and we need to
> > check the error to decide calling f2fs_balance_fs() in line 222, since
> > set_new_dnode() is used to set all the fields in dnode_of_data. So, if you
> > don't mind, could you please post a patch?
> 
> Just to clarify, just setting dn.node_changes to false is enough?
> 
> I'm not entirely sure what you meant when you wrote "and we need to
> check the error to decide calling f2fs_balance_fs() in line 222".

I meant:

222	if (!err)
223		f2fs_balance_fs(sbi, dn.node_changed);

Thanks,

> 
> Colin
> 
> > 
> > Thanks,
> > 
> >>
> >> Colin
> >>