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Message-ID: <CAD+ocbwyE=h3jFnanQRqkh+AemCv8aP2W9J92C4OoV047TZS7Q@mail.gmail.com>
Date: Wed, 12 Jan 2022 20:17:54 -0800
From: harshad shirwadkar <harshadshirwadkar@...il.com>
To: Xin Yin <yinxin.x@...edance.com>
Cc: Dan Carpenter <dan.carpenter@...cle.com>, kbuild@...ts.01.org,
"Theodore Y. Ts'o" <tytso@....edu>,
Andreas Dilger <adilger.kernel@...ger.ca>,
kbuild test robot <lkp@...el.com>, kbuild-all@...ts.01.org,
Ext4 Developers List <linux-ext4@...r.kernel.org>,
linux-kernel@...r.kernel.org
Subject: Re: [External] Re: [PATCH 1/2] ext4: fast commit may not fallback for
ineligible commit
On Mon, Jan 10, 2022 at 7:13 PM Xin Yin <yinxin.x@...edance.com> wrote:
>
> Hi Dan,
>
> Thanks for spotting this, and I think it is not only an
> 'uninitialized' issue , we can not use 'handle' after
> ext4_journal_stop, it may cause a use-after-free.
> So maybe we should use 'transaction tid' as input instead of 'handle',
> then it will be like this ext4_fc_mark_ineligible(struct super_block
> *sb, int reason, tid_t tid). or we should move all
> ext4_fc_mark_ineligible() between ext4_journal_start/ext4_journal_stop
> if we need 'handle' param.
This is a case where the inode is still in the fast commit list and we
reached the "no_delete" case in ext4_evict_inode. Note that we reach
here even when we are not able to start the journal handle. So, the
second option that you suggested (to move ext4_fc_mark_ineligible()
between ext4_journal_start() and ext4_journal_stop()) would not work
for the case when we are not able to start the handle at all. Also,
passing handle to ext4_fc_mark_ineligible() is pretty clean so I'd
like to stay with that instead of passing "tid".
How about adding a new variant of ext4_fc_mark_ineligible() that
doesn't take handle and only takes sb and reason? In that function we
can mark the currently running transaction as ineligible. So basically
it would derive tid as journal->j_running_transaction->t_tid. We can
name that function as something like "ext4_fc_mark_txn_ineligible()".
>
> Hi Harshad, could you give some advice? it seems you also need to
> change this part in your following patches.
>
> Thanks,
> Xin Yin
>
> On Mon, Jan 10, 2022 at 5:23 PM Dan Carpenter <dan.carpenter@...cle.com> wrote:
> >
> > Hi Xin,
> >
> > url: https://github.com/0day-ci/linux/commits/Xin-Yin/ext4-fix-issues-when-fast-commit-work-with-jbd/20220107-201314
> > base: https://git.kernel.org/pub/scm/linux/kernel/git/tytso/ext4.git dev
> > config: x86_64-randconfig-m001-20220107 (https://download.01.org/0day-ci/archive/20220109/202201091544.W5HHEXAp-lkp@intel.com/config)
> > compiler: gcc-9 (Debian 9.3.0-22) 9.3.0
> >
> > If you fix the issue, kindly add following tag as appropriate
> > Reported-by: kernel test robot <lkp@...el.com>
> > Reported-by: Dan Carpenter <dan.carpenter@...cle.com>
> >
> > New smatch warnings:
> > fs/ext4/inode.c:340 ext4_evict_inode() error: uninitialized symbol 'handle'.
> >
> > vim +/handle +340 fs/ext4/inode.c
> >
> > 0930fcc1ee2f0a Al Viro 2010-06-07 167 void ext4_evict_inode(struct inode *inode)
> > ac27a0ec112a08 Dave Kleikamp 2006-10-11 168 {
> > ac27a0ec112a08 Dave Kleikamp 2006-10-11 169 handle_t *handle;
> > bc965ab3f2b4b7 Theodore Ts'o 2008-08-02 170 int err;
> > 65db869c754e7c Jan Kara 2019-11-05 171 /*
> > 65db869c754e7c Jan Kara 2019-11-05 172 * Credits for final inode cleanup and freeing:
> > 65db869c754e7c Jan Kara 2019-11-05 173 * sb + inode (ext4_orphan_del()), block bitmap, group descriptor
> > 65db869c754e7c Jan Kara 2019-11-05 174 * (xattr block freeing), bitmap, group descriptor (inode freeing)
> > 65db869c754e7c Jan Kara 2019-11-05 175 */
> > 65db869c754e7c Jan Kara 2019-11-05 176 int extra_credits = 6;
> > 0421a189bc8cde Tahsin Erdogan 2017-06-22 177 struct ext4_xattr_inode_array *ea_inode_array = NULL;
> > 46e294efc355c4 Jan Kara 2020-11-27 178 bool freeze_protected = false;
> > ac27a0ec112a08 Dave Kleikamp 2006-10-11 179
> > 7ff9c073dd4d72 Theodore Ts'o 2010-11-08 180 trace_ext4_evict_inode(inode);
> > 2581fdc810889f Jiaying Zhang 2011-08-13 181
> > 0930fcc1ee2f0a Al Viro 2010-06-07 182 if (inode->i_nlink) {
> > 2d859db3e4a82a Jan Kara 2011-07-26 183 /*
> > 2d859db3e4a82a Jan Kara 2011-07-26 184 * When journalling data dirty buffers are tracked only in the
> > 2d859db3e4a82a Jan Kara 2011-07-26 185 * journal. So although mm thinks everything is clean and
> > 2d859db3e4a82a Jan Kara 2011-07-26 186 * ready for reaping the inode might still have some pages to
> > 2d859db3e4a82a Jan Kara 2011-07-26 187 * write in the running transaction or waiting to be
> > 2d859db3e4a82a Jan Kara 2011-07-26 188 * checkpointed. Thus calling jbd2_journal_invalidatepage()
> > 2d859db3e4a82a Jan Kara 2011-07-26 189 * (via truncate_inode_pages()) to discard these buffers can
> > 2d859db3e4a82a Jan Kara 2011-07-26 190 * cause data loss. Also even if we did not discard these
> > 2d859db3e4a82a Jan Kara 2011-07-26 191 * buffers, we would have no way to find them after the inode
> > 2d859db3e4a82a Jan Kara 2011-07-26 192 * is reaped and thus user could see stale data if he tries to
> > 2d859db3e4a82a Jan Kara 2011-07-26 193 * read them before the transaction is checkpointed. So be
> > 2d859db3e4a82a Jan Kara 2011-07-26 194 * careful and force everything to disk here... We use
> > 2d859db3e4a82a Jan Kara 2011-07-26 195 * ei->i_datasync_tid to store the newest transaction
> > 2d859db3e4a82a Jan Kara 2011-07-26 196 * containing inode's data.
> > 2d859db3e4a82a Jan Kara 2011-07-26 197 *
> > 2d859db3e4a82a Jan Kara 2011-07-26 198 * Note that directories do not have this problem because they
> > 2d859db3e4a82a Jan Kara 2011-07-26 199 * don't use page cache.
> > 2d859db3e4a82a Jan Kara 2011-07-26 200 */
> > 6a7fd522a7c94c Vegard Nossum 2016-07-04 201 if (inode->i_ino != EXT4_JOURNAL_INO &&
> > 6a7fd522a7c94c Vegard Nossum 2016-07-04 202 ext4_should_journal_data(inode) &&
> > 3abb1a0fc2871f Jan Kara 2017-06-22 203 (S_ISLNK(inode->i_mode) || S_ISREG(inode->i_mode)) &&
> > 3abb1a0fc2871f Jan Kara 2017-06-22 204 inode->i_data.nrpages) {
> > 2d859db3e4a82a Jan Kara 2011-07-26 205 journal_t *journal = EXT4_SB(inode->i_sb)->s_journal;
> > 2d859db3e4a82a Jan Kara 2011-07-26 206 tid_t commit_tid = EXT4_I(inode)->i_datasync_tid;
> > 2d859db3e4a82a Jan Kara 2011-07-26 207
> > d76a3a77113db0 Theodore Ts'o 2013-04-03 208 jbd2_complete_transaction(journal, commit_tid);
> > 2d859db3e4a82a Jan Kara 2011-07-26 209 filemap_write_and_wait(&inode->i_data);
> > 2d859db3e4a82a Jan Kara 2011-07-26 210 }
> > 91b0abe36a7b2b Johannes Weiner 2014-04-03 211 truncate_inode_pages_final(&inode->i_data);
> > 5dc23bdd5f846e Jan Kara 2013-06-04 212
> > 0930fcc1ee2f0a Al Viro 2010-06-07 213 goto no_delete;
> >
> > Assume we hit this goto
> >
> > 0930fcc1ee2f0a Al Viro 2010-06-07 214 }
> > 0930fcc1ee2f0a Al Viro 2010-06-07 215
> > e2bfb088fac03c Theodore Ts'o 2014-10-05 216 if (is_bad_inode(inode))
> > e2bfb088fac03c Theodore Ts'o 2014-10-05 217 goto no_delete;
> > 871a293155a245 Christoph Hellwig 2010-03-03 218 dquot_initialize(inode);
> > 907f4554e2521c Christoph Hellwig 2010-03-03 219
> > 678aaf481496b0 Jan Kara 2008-07-11 220 if (ext4_should_order_data(inode))
> > 678aaf481496b0 Jan Kara 2008-07-11 221 ext4_begin_ordered_truncate(inode, 0);
> > 91b0abe36a7b2b Johannes Weiner 2014-04-03 222 truncate_inode_pages_final(&inode->i_data);
> > ac27a0ec112a08 Dave Kleikamp 2006-10-11 223
> > ceff86fddae874 Jan Kara 2020-04-21 224 /*
> > ceff86fddae874 Jan Kara 2020-04-21 225 * For inodes with journalled data, transaction commit could have
> > ceff86fddae874 Jan Kara 2020-04-21 226 * dirtied the inode. Flush worker is ignoring it because of I_FREEING
> > ceff86fddae874 Jan Kara 2020-04-21 227 * flag but we still need to remove the inode from the writeback lists.
> > ceff86fddae874 Jan Kara 2020-04-21 228 */
> > ceff86fddae874 Jan Kara 2020-04-21 229 if (!list_empty_careful(&inode->i_io_list)) {
> > ceff86fddae874 Jan Kara 2020-04-21 230 WARN_ON_ONCE(!ext4_should_journal_data(inode));
> > ceff86fddae874 Jan Kara 2020-04-21 231 inode_io_list_del(inode);
> > ceff86fddae874 Jan Kara 2020-04-21 232 }
> > ceff86fddae874 Jan Kara 2020-04-21 233
> > 8e8ad8a57c75f3 Jan Kara 2012-06-12 234 /*
> > 8e8ad8a57c75f3 Jan Kara 2012-06-12 235 * Protect us against freezing - iput() caller didn't have to have any
> > 46e294efc355c4 Jan Kara 2020-11-27 236 * protection against it. When we are in a running transaction though,
> > 46e294efc355c4 Jan Kara 2020-11-27 237 * we are already protected against freezing and we cannot grab further
> > 46e294efc355c4 Jan Kara 2020-11-27 238 * protection due to lock ordering constraints.
> > 8e8ad8a57c75f3 Jan Kara 2012-06-12 239 */
> > 46e294efc355c4 Jan Kara 2020-11-27 240 if (!ext4_journal_current_handle()) {
> > 8e8ad8a57c75f3 Jan Kara 2012-06-12 241 sb_start_intwrite(inode->i_sb);
> > 46e294efc355c4 Jan Kara 2020-11-27 242 freeze_protected = true;
> > 46e294efc355c4 Jan Kara 2020-11-27 243 }
> > e50e5129f384ae Andreas Dilger 2017-06-21 244
> > 30a7eb970c3aae Tahsin Erdogan 2017-06-22 245 if (!IS_NOQUOTA(inode))
> > 30a7eb970c3aae Tahsin Erdogan 2017-06-22 246 extra_credits += EXT4_MAXQUOTAS_DEL_BLOCKS(inode->i_sb);
> > 30a7eb970c3aae Tahsin Erdogan 2017-06-22 247
> > 65db869c754e7c Jan Kara 2019-11-05 248 /*
> > 65db869c754e7c Jan Kara 2019-11-05 249 * Block bitmap, group descriptor, and inode are accounted in both
> > 65db869c754e7c Jan Kara 2019-11-05 250 * ext4_blocks_for_truncate() and extra_credits. So subtract 3.
> > 65db869c754e7c Jan Kara 2019-11-05 251 */
> > 30a7eb970c3aae Tahsin Erdogan 2017-06-22 252 handle = ext4_journal_start(inode, EXT4_HT_TRUNCATE,
> > 65db869c754e7c Jan Kara 2019-11-05 253 ext4_blocks_for_truncate(inode) + extra_credits - 3);
> > ac27a0ec112a08 Dave Kleikamp 2006-10-11 254 if (IS_ERR(handle)) {
> > bc965ab3f2b4b7 Theodore Ts'o 2008-08-02 255 ext4_std_error(inode->i_sb, PTR_ERR(handle));
> > ac27a0ec112a08 Dave Kleikamp 2006-10-11 256 /*
> > ac27a0ec112a08 Dave Kleikamp 2006-10-11 257 * If we're going to skip the normal cleanup, we still need to
> > ac27a0ec112a08 Dave Kleikamp 2006-10-11 258 * make sure that the in-core orphan linked list is properly
> > ac27a0ec112a08 Dave Kleikamp 2006-10-11 259 * cleaned up.
> > ac27a0ec112a08 Dave Kleikamp 2006-10-11 260 */
> > 617ba13b31fbf5 Mingming Cao 2006-10-11 261 ext4_orphan_del(NULL, inode);
> > 46e294efc355c4 Jan Kara 2020-11-27 262 if (freeze_protected)
> > 8e8ad8a57c75f3 Jan Kara 2012-06-12 263 sb_end_intwrite(inode->i_sb);
> > ac27a0ec112a08 Dave Kleikamp 2006-10-11 264 goto no_delete;
> > ac27a0ec112a08 Dave Kleikamp 2006-10-11 265 }
> > 30a7eb970c3aae Tahsin Erdogan 2017-06-22 266
> > ac27a0ec112a08 Dave Kleikamp 2006-10-11 267 if (IS_SYNC(inode))
> > 0390131ba84fd3 Frank Mayhar 2009-01-07 268 ext4_handle_sync(handle);
> > 407cd7fb83c0eb Tahsin Erdogan 2017-07-04 269
> > 407cd7fb83c0eb Tahsin Erdogan 2017-07-04 270 /*
> > 407cd7fb83c0eb Tahsin Erdogan 2017-07-04 271 * Set inode->i_size to 0 before calling ext4_truncate(). We need
> > 407cd7fb83c0eb Tahsin Erdogan 2017-07-04 272 * special handling of symlinks here because i_size is used to
> > 407cd7fb83c0eb Tahsin Erdogan 2017-07-04 273 * determine whether ext4_inode_info->i_data contains symlink data or
> > 407cd7fb83c0eb Tahsin Erdogan 2017-07-04 274 * block mappings. Setting i_size to 0 will remove its fast symlink
> > 407cd7fb83c0eb Tahsin Erdogan 2017-07-04 275 * status. Erase i_data so that it becomes a valid empty block map.
> > 407cd7fb83c0eb Tahsin Erdogan 2017-07-04 276 */
> > 407cd7fb83c0eb Tahsin Erdogan 2017-07-04 277 if (ext4_inode_is_fast_symlink(inode))
> > 407cd7fb83c0eb Tahsin Erdogan 2017-07-04 278 memset(EXT4_I(inode)->i_data, 0, sizeof(EXT4_I(inode)->i_data));
> > ac27a0ec112a08 Dave Kleikamp 2006-10-11 279 inode->i_size = 0;
> > bc965ab3f2b4b7 Theodore Ts'o 2008-08-02 280 err = ext4_mark_inode_dirty(handle, inode);
> > bc965ab3f2b4b7 Theodore Ts'o 2008-08-02 281 if (err) {
> > 12062dddda4509 Eric Sandeen 2010-02-15 282 ext4_warning(inode->i_sb,
> > bc965ab3f2b4b7 Theodore Ts'o 2008-08-02 283 "couldn't mark inode dirty (err %d)", err);
> > bc965ab3f2b4b7 Theodore Ts'o 2008-08-02 284 goto stop_handle;
> > bc965ab3f2b4b7 Theodore Ts'o 2008-08-02 285 }
> > 2c98eb5ea24976 Theodore Ts'o 2016-11-13 286 if (inode->i_blocks) {
> > 2c98eb5ea24976 Theodore Ts'o 2016-11-13 287 err = ext4_truncate(inode);
> > 2c98eb5ea24976 Theodore Ts'o 2016-11-13 288 if (err) {
> > 54d3adbc29f0c7 Theodore Ts'o 2020-03-28 289 ext4_error_err(inode->i_sb, -err,
> > 2c98eb5ea24976 Theodore Ts'o 2016-11-13 290 "couldn't truncate inode %lu (err %d)",
> > 2c98eb5ea24976 Theodore Ts'o 2016-11-13 291 inode->i_ino, err);
> > 2c98eb5ea24976 Theodore Ts'o 2016-11-13 292 goto stop_handle;
> > 2c98eb5ea24976 Theodore Ts'o 2016-11-13 293 }
> > 2c98eb5ea24976 Theodore Ts'o 2016-11-13 294 }
> > bc965ab3f2b4b7 Theodore Ts'o 2008-08-02 295
> > 30a7eb970c3aae Tahsin Erdogan 2017-06-22 296 /* Remove xattr references. */
> > 30a7eb970c3aae Tahsin Erdogan 2017-06-22 297 err = ext4_xattr_delete_inode(handle, inode, &ea_inode_array,
> > 30a7eb970c3aae Tahsin Erdogan 2017-06-22 298 extra_credits);
> > 30a7eb970c3aae Tahsin Erdogan 2017-06-22 299 if (err) {
> > 30a7eb970c3aae Tahsin Erdogan 2017-06-22 300 ext4_warning(inode->i_sb, "xattr delete (err %d)", err);
> > bc965ab3f2b4b7 Theodore Ts'o 2008-08-02 301 stop_handle:
> > bc965ab3f2b4b7 Theodore Ts'o 2008-08-02 302 ext4_journal_stop(handle);
> > 4538821993f448 Theodore Ts'o 2010-07-29 303 ext4_orphan_del(NULL, inode);
> > 46e294efc355c4 Jan Kara 2020-11-27 304 if (freeze_protected)
> > 8e8ad8a57c75f3 Jan Kara 2012-06-12 305 sb_end_intwrite(inode->i_sb);
> > 30a7eb970c3aae Tahsin Erdogan 2017-06-22 306 ext4_xattr_inode_array_free(ea_inode_array);
> > bc965ab3f2b4b7 Theodore Ts'o 2008-08-02 307 goto no_delete;
> > bc965ab3f2b4b7 Theodore Ts'o 2008-08-02 308 }
> > bc965ab3f2b4b7 Theodore Ts'o 2008-08-02 309
> > ac27a0ec112a08 Dave Kleikamp 2006-10-11 310 /*
> > 617ba13b31fbf5 Mingming Cao 2006-10-11 311 * Kill off the orphan record which ext4_truncate created.
> > ac27a0ec112a08 Dave Kleikamp 2006-10-11 312 * AKPM: I think this can be inside the above `if'.
> > 617ba13b31fbf5 Mingming Cao 2006-10-11 313 * Note that ext4_orphan_del() has to be able to cope with the
> > ac27a0ec112a08 Dave Kleikamp 2006-10-11 314 * deletion of a non-existent orphan - this is because we don't
> > 617ba13b31fbf5 Mingming Cao 2006-10-11 315 * know if ext4_truncate() actually created an orphan record.
> > ac27a0ec112a08 Dave Kleikamp 2006-10-11 316 * (Well, we could do this if we need to, but heck - it works)
> > ac27a0ec112a08 Dave Kleikamp 2006-10-11 317 */
> > 617ba13b31fbf5 Mingming Cao 2006-10-11 318 ext4_orphan_del(handle, inode);
> > 5ffff834322281 Arnd Bergmann 2018-07-29 319 EXT4_I(inode)->i_dtime = (__u32)ktime_get_real_seconds();
> > ac27a0ec112a08 Dave Kleikamp 2006-10-11 320
> > ac27a0ec112a08 Dave Kleikamp 2006-10-11 321 /*
> > ac27a0ec112a08 Dave Kleikamp 2006-10-11 322 * One subtle ordering requirement: if anything has gone wrong
> > ac27a0ec112a08 Dave Kleikamp 2006-10-11 323 * (transaction abort, IO errors, whatever), then we can still
> > ac27a0ec112a08 Dave Kleikamp 2006-10-11 324 * do these next steps (the fs will already have been marked as
> > ac27a0ec112a08 Dave Kleikamp 2006-10-11 325 * having errors), but we can't free the inode if the mark_dirty
> > ac27a0ec112a08 Dave Kleikamp 2006-10-11 326 * fails.
> > ac27a0ec112a08 Dave Kleikamp 2006-10-11 327 */
> > 617ba13b31fbf5 Mingming Cao 2006-10-11 328 if (ext4_mark_inode_dirty(handle, inode))
> > ac27a0ec112a08 Dave Kleikamp 2006-10-11 329 /* If that failed, just do the required in-core inode clear. */
> > 0930fcc1ee2f0a Al Viro 2010-06-07 330 ext4_clear_inode(inode);
> > ac27a0ec112a08 Dave Kleikamp 2006-10-11 331 else
> > 617ba13b31fbf5 Mingming Cao 2006-10-11 332 ext4_free_inode(handle, inode);
> > 617ba13b31fbf5 Mingming Cao 2006-10-11 333 ext4_journal_stop(handle);
> > 46e294efc355c4 Jan Kara 2020-11-27 334 if (freeze_protected)
> > 8e8ad8a57c75f3 Jan Kara 2012-06-12 335 sb_end_intwrite(inode->i_sb);
> > 0421a189bc8cde Tahsin Erdogan 2017-06-22 336 ext4_xattr_inode_array_free(ea_inode_array);
> > ac27a0ec112a08 Dave Kleikamp 2006-10-11 337 return;
> > ac27a0ec112a08 Dave Kleikamp 2006-10-11 338 no_delete:
> > b21ebf143af219 Harshad Shirwadkar 2020-11-05 339 if (!list_empty(&EXT4_I(inode)->i_fc_list))
> >
> > It's not clear without more context where this ->i_fc_list list is
> > modified.
> >
> > db40129f85538a Xin Yin 2022-01-07 @340 ext4_fc_mark_ineligible(inode->i_sb, EXT4_FC_REASON_NOMEM, handle);
> >
> > "handle" might be uninitialized?
> >
> > 0930fcc1ee2f0a Al Viro 2010-06-07 341 ext4_clear_inode(inode); /* We must guarantee clearing of inode... */
> > 9d0be50230b333 Theodore Ts'o 2010-01-01 342 }
> >
> > ---
> > 0-DAY CI Kernel Test Service, Intel Corporation
> > https://lists.01.org/hyperkitty/list/kbuild-all@lists.01.org
> >
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