This is a note to let you know that I've just added the patch titled
nilfs2: do not force clear folio if buffer is referenced
to the 6.13-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
nilfs2-do-not-force-clear-folio-if-buffer-is-referen.patch
and it can be found in the queue-6.13 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
commit 6dcafd41d5fbaf3e45a29dae2274274befdfe6ed
Author: Ryusuke Konishi <konishi.ryusuke@xxxxxxxxx>
Date: Wed Jan 8 05:00:46 2025 +0900
nilfs2: do not force clear folio if buffer is referenced
[ Upstream commit 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@xxxxxxxxx
Link: https://lkml.kernel.org/r/20250107200202.6432-2-konishi.ryusuke@xxxxxxxxx
Signed-off-by: Ryusuke Konishi <konishi.ryusuke@xxxxxxxxx>
Reported-by: syzbot+b2b14916b77acf8626d7@xxxxxxxxxxxxxxxxxxxxxxxxx
Closes: https://syzkaller.appspot.com/bug?extid=b2b14916b77acf8626d7
Reported-by: syzbot+d98fd19acd08b36ff422@xxxxxxxxxxxxxxxxxxxxxxxxx
Link: https://syzkaller.appspot.com/bug?extid=d98fd19acd08b36ff422
Fixes: 8c26c4e2694a ("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@xxxxxxxxxxxxxxxxxxxxxxxxx
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
diff --git a/fs/nilfs2/page.c b/fs/nilfs2/page.c
index 9de2a494a0694..899686d2e5f71 100644
--- a/fs/nilfs2/page.c
+++ b/fs/nilfs2/page.c
@@ -392,6 +392,11 @@ void nilfs_clear_dirty_pages(struct address_space *mapping)
/**
* nilfs_clear_folio_dirty - discard dirty folio
* @folio: dirty folio that will be discarded
+ *
+ * nilfs_clear_folio_dirty() clears working states including dirty state for
+ * the folio and its buffers. If the folio 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_folio_dirty(struct folio *folio)
{
@@ -399,10 +404,6 @@ void nilfs_clear_folio_dirty(struct folio *folio)
BUG_ON(!folio_test_locked(folio));
- folio_clear_uptodate(folio);
- folio_clear_mappedtodisk(folio);
- folio_clear_checked(folio);
-
head = folio_buffers(folio);
if (head) {
const unsigned long clear_bits =
@@ -410,6 +411,25 @@ void nilfs_clear_folio_dirty(struct folio *folio)
BIT(BH_Async_Write) | BIT(BH_NILFS_Volatile) |
BIT(BH_NILFS_Checked) | BIT(BH_NILFS_Redirected) |
BIT(BH_Delay));
+ bool busy, invalidated = false;
+
+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 {
@@ -419,6 +439,9 @@ void nilfs_clear_folio_dirty(struct folio *folio)
} while (bh = bh->b_this_page, bh != head);
}
+ folio_clear_uptodate(folio);
+ folio_clear_mappedtodisk(folio);
+ folio_clear_checked(folio);
__nilfs_clear_folio_dirty(folio);
}
