Commit 4d09b5ef authored Mar 26, 2025 by Ryusuke Konishi Committed by Liu Chuang Mar 26, 2025

nilfs2: do not force clear folio if buffer is referenced

mainline inclusion
from mainline-v6.14-rc1
commit ca76bb226bf47ff04c782cacbd299f12ddee1ec1
category: bugfix
bugzilla: https://gitee.com/src-openeuler/kernel/issues/IBPBK0
CVE: CVE-2025-21722

Reference: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=ca76bb226bf47ff04c782cacbd299f12ddee1ec1

----------------------

Patch series "nilfs2: protect busy buffer heads from being force-cleared".

This series fixes the buffer head state inconsistency issues reported by
syzbot that occurs when the filesystem is corrupted and falls back to
read-only, and the associated buffer head use-after-free issue.

This patch (of 2):

Syzbot has reported that after nilfs2 detects filesystem corruption and
falls back to read-only, inconsistencies in the buffer state may occur.

One of the inconsistencies is that when nilfs2 calls mark_buffer_dirty()
to set a data or metadata buffer as dirty, but it detects that the buffer
is not in the uptodate state:

 WARNING: CPU: 0 PID: 6049 at fs/buffer.c:1177 mark_buffer_dirty+0x2e5/0x520
  fs/buffer.c:1177
 ...
 Call Trace:
  <TASK>
  nilfs_palloc_commit_alloc_entry+0x4b/0x160 fs/nilfs2/alloc.c:598
  nilfs_ifile_create_inode+0x1dd/0x3a0 fs/nilfs2/ifile.c:73
  nilfs_new_inode+0x254/0x830 fs/nilfs2/inode.c:344
  nilfs_mkdir+0x10d/0x340 fs/nilfs2/namei.c:218
  vfs_mkdir+0x2f9/0x4f0 fs/namei.c:4257
  do_mkdirat+0x264/0x3a0 fs/namei.c:4280
  __do_sys_mkdirat fs/namei.c:4295 [inline]
  __se_sys_mkdirat fs/namei.c:4293 [inline]
  __x64_sys_mkdirat+0x87/0xa0 fs/namei.c:4293
  do_syscall_x64 arch/x86/entry/common.c:52 [inline]
  do_syscall_64+0xf3/0x230 arch/x86/entry/common.c:83
  entry_SYSCALL_64_after_hwframe+0x77/0x7f

The other is when nilfs_btree_propagate(), which propagates the dirty
state to the ancestor nodes of a b-tree that point to a dirty buffer,
detects that the origin buffer is not dirty, even though it should be:

 WARNING: CPU: 0 PID: 5245 at fs/nilfs2/btree.c:2089
  nilfs_btree_propagate+0xc79/0xdf0 fs/nilfs2/btree.c:2089
 ...
 Call Trace:
  <TASK>
  nilfs_bmap_propagate+0x75/0x120 fs/nilfs2/bmap.c:345
  nilfs_collect_file_data+0x4d/0xd0 fs/nilfs2/segment.c:587
  nilfs_segctor_apply_buffers+0x184/0x340 fs/nilfs2/segment.c:1006
  nilfs_segctor_scan_file+0x28c/0xa50 fs/nilfs2/segment.c:1045
  nilfs_segctor_collect_blocks fs/nilfs2/segment.c:1216 [inline]
  nilfs_segctor_collect fs/nilfs2/segment.c:1540 [inline]
  nilfs_segctor_do_construct+0x1c28/0x6b90 fs/nilfs2/segment.c:2115
  nilfs_segctor_construct+0x181/0x6b0 fs/nilfs2/segment.c:2479
  nilfs_segctor_thread_construct fs/nilfs2/segment.c:2587 [inline]
  nilfs_segctor_thread+0x69e/0xe80 fs/nilfs2/segment.c:2701
  kthread+0x2f0/0x390 kernel/kthread.c:389
  ret_from_fork+0x4b/0x80 arch/x86/kernel/process.c:147
  ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:244
  </TASK>

Both of these issues are caused by the callbacks that handle the
page/folio write requests, forcibly clear various states, including the
working state of the buffers they hold, at unexpected times when they
detect read-only fallback.

Fix these issues by checking if the buffer is referenced before clearing
the page/folio state, and skipping the clear if it is.

Link: https://lkml.kernel.org/r/20250107200202.6432-1-konishi.ryusuke@gmail.com
Link: https://lkml.kernel.org/r/20250107200202.6432-2-konishi.ryusuke@gmail.com


Signed-off-by: Ryusuke Konishi <konishi.ryusuke@gmail.com>
Reported-by:  <syzbot+b2b14916b77acf8626d7@syzkaller.appspotmail.com>
Closes: https://syzkaller.appspot.com/bug?extid=b2b14916b77acf8626d7


Reported-by:  <syzbot+d98fd19acd08b36ff422@syzkaller.appspotmail.com>
Link: https://syzkaller.appspot.com/bug?extid=d98fd19acd08b36ff422


Fixes: 8c26c4e2 ("nilfs2: fix issue with flush kernel thread after remount in RO mode because of driver's internal error or metadata corruption")
Tested-by:  <syzbot+b2b14916b77acf8626d7@syzkaller.appspotmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Conflicts:
	fs/nilfs2/page.c
[Due to previous commits not merged.]
Signed-off-by: Liu Chuang <liuchuang40@huawei.com>

parent afadf562

fs/nilfs2/page.c

+31 −5

Original line number	Diff line number	Diff line
		@@ -383,6 +383,11 @@ void nilfs_clear_dirty_pages(struct address_space *mapping, bool silent)
		* nilfs_clear_dirty_page - discard dirty page
		* @page: dirty page that will be discarded
		* @silent: suppress [true] or print [false] warning messages
		*
		* nilfs_clear_dirty_page() clears working states including dirty state for
		* the page and its buffers. If the page has buffers, clear only if it is
		* confirmed that none of the buffer heads are busy (none have valid
		* references and none are locked).
		*/
		void nilfs_clear_dirty_page(struct page *page, bool silent)
		{
		@@ -396,18 +401,35 @@ void nilfs_clear_dirty_page(struct page *page, bool silent)
		"discard dirty page: offset=%lld, ino=%lu",
		page_offset(page), inode->i_ino);

		ClearPageUptodate(page);
		ClearPageMappedToDisk(page);
		ClearPageChecked(page);

		if (page_has_buffers(page)) {
		struct buffer_head bh, head;
		const unsigned long clear_bits =
		(BIT(BH_Uptodate) \| BIT(BH_Dirty) \| BIT(BH_Mapped) \|
		BIT(BH_Async_Write) \| BIT(BH_NILFS_Volatile) \|
		BIT(BH_NILFS_Checked) \| BIT(BH_NILFS_Redirected));
		bool busy, invalidated = false;

		bh = head = page_buffers(page);
		head = page_buffers(page);

		recheck_buffers:
		busy = false;
		bh = head;
		do {
		if (atomic_read(&bh->b_count) \| buffer_locked(bh)) {
		busy = true;
		break;
		}
		} while (bh = bh->b_this_page, bh != head);

		if (busy) {
		if (invalidated)
		return;
		invalidate_bh_lrus();
		invalidated = true;
		goto recheck_buffers;
		}

		bh = head;
		do {
		lock_buffer(bh);
		if (!silent)
		@@ -420,6 +442,10 @@ void nilfs_clear_dirty_page(struct page *page, bool silent)
		} while (bh = bh->b_this_page, bh != head);
		}

		ClearPageUptodate(page);
		ClearPageMappedToDisk(page);
		ClearPageChecked(page);

		__nilfs_clear_page_dirty(page);
		}