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nilfs2: do not force clear folio if buffer is referenced

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commit ca76bb226b upstream.

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.

[konishi.ryusuke@gmail.com: adjusted for page/folio conversion]
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: 8c26c4e269 ("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>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Ryusuke Konishi 2025-02-07 03:14:31 +09:00 committed by Greg Kroah-Hartman
parent 217114cf30
commit 1929673702
1 changed files with 29 additions and 6 deletions
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35
fs/nilfs2/page.c
View File

@ -388,24 +388,44 @@ void nilfs_clear_dirty_pages(struct address_space *mapping)
/**
* nilfs_clear_dirty_page - discard dirty page
* @page: dirty page that will be discarded
*
* 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)
{
BUG_ON(!PageLocked(page));
ClearPageUptodate(page);
ClearPageMappedToDisk(page);
ClearPageChecked(page);
if (page_has_buffers(page)) {
struct buffer_head *bh, *head;
struct buffer_head *bh, *head = page_buffers(page);
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) |
BIT(BH_Delay));
bool busy, invalidated = false;
bh = 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);
set_mask_bits(&bh->b_state, clear_bits, 0);
@ -413,6 +433,9 @@ void nilfs_clear_dirty_page(struct page *page)
} while (bh = bh->b_this_page, bh != head);
}
ClearPageUptodate(page);
ClearPageMappedToDisk(page);
ClearPageChecked(page);
__nilfs_clear_page_dirty(page);
}