The patch titled Subject: nilfs2: fix WARNING in mark_buffer_dirty due to discarded buffer reuse has been added to the -mm mm-hotfixes-unstable branch. Its filename is nilfs2-fix-warning-in-mark_buffer_dirty-due-to-discarded-buffer-reuse.patch

This patch will shortly appear at https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches...

This patch will later appear in the mm-hotfixes-unstable branch at git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm

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------------------------------------------------------ From: Ryusuke Konishi konishi.ryusuke@gmail.com Subject: nilfs2: fix WARNING in mark_buffer_dirty due to discarded buffer reuse Date: Fri, 18 Aug 2023 22:18:04 +0900

A syzbot stress test using a corrupted disk image reported that mark_buffer_dirty() called from __nilfs_mark_inode_dirty() or nilfs_palloc_commit_alloc_entry() may output a kernel warning, and can panic if the kernel is booted with panic_on_warn.

This is because nilfs2 keeps buffer pointers in local structures for some metadata and reuses them, but such buffers may be forcibly discarded by nilfs_clear_dirty_page() in some critical situations.

This issue is reported to appear after commit 28a65b49eb53 ("nilfs2: do not write dirty data after degenerating to read-only"), but the issue has potentially existed before.

Fix this issue by checking the uptodate flag when attempting to reuse an internally held buffer, and reloading the metadata instead of reusing the buffer if the flag was lost.

Link: https://lkml.kernel.org/r/20230818131804.7758-1-konishi.ryusuke@gmail.com Signed-off-by: Ryusuke Konishi konishi.ryusuke@gmail.com Reported-by: syzbot+cdfcae656bac88ba0e2d@syzkaller.appspotmail.com Closes: https://lkml.kernel.org/r/0000000000003da75f05fdeffd12@google.com 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: Ryusuke Konishi konishi.ryusuke@gmail.com Cc: stable@vger.kernel.org # 3.10+ Signed-off-by: Andrew Morton akpm@linux-foundation.org ---

fs/nilfs2/alloc.c | 3 ++- fs/nilfs2/inode.c | 7 +++++-- 2 files changed, 7 insertions(+), 3 deletions(-)

--- a/fs/nilfs2/alloc.c~nilfs2-fix-warning-in-mark_buffer_dirty-due-to-discarded-buffer-reuse +++ a/fs/nilfs2/alloc.c @@ -205,7 +205,8 @@ static int nilfs_palloc_get_block(struct int ret;

spin_lock(lock); - if (prev->bh && blkoff == prev->blkoff) { + if (prev->bh && blkoff == prev->blkoff && + likely(buffer_uptodate(prev->bh))) { get_bh(prev->bh); *bhp = prev->bh; spin_unlock(lock); --- a/fs/nilfs2/inode.c~nilfs2-fix-warning-in-mark_buffer_dirty-due-to-discarded-buffer-reuse +++ a/fs/nilfs2/inode.c @@ -1025,7 +1025,7 @@ int nilfs_load_inode_block(struct inode int err;

spin_lock(&nilfs->ns_inode_lock); - if (ii->i_bh == NULL) { + if (ii->i_bh == NULL || unlikely(!buffer_uptodate(ii->i_bh))) { spin_unlock(&nilfs->ns_inode_lock); err = nilfs_ifile_get_inode_block(ii->i_root->ifile, inode->i_ino, pbh); @@ -1034,7 +1034,10 @@ int nilfs_load_inode_block(struct inode spin_lock(&nilfs->ns_inode_lock); if (ii->i_bh == NULL) ii->i_bh = *pbh; - else { + else if (unlikely(!buffer_uptodate(ii->i_bh))) { + __brelse(ii->i_bh); + ii->i_bh = *pbh; + } else { brelse(*pbh); *pbh = ii->i_bh; } _

Patches currently in -mm which might be from konishi.ryusuke@gmail.com are

nilfs2-fix-general-protection-fault-in-nilfs_lookup_dirty_data_buffers.patch nilfs2-fix-warning-in-mark_buffer_dirty-due-to-discarded-buffer-reuse.patch