nilfs2: fix WARNING in mark_buffer_dirty due to discarded buffer reuse

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>

diff --git a/fs/nilfs2/alloc.c b/fs/nilfs2/alloc.c
index 6ce8617b562d5ffb6a79af75c1aaf35d9f37c9f9..7342de296ec3c6a8486da9f6bb0b16eeded7ca5c 100644 (file)
--- a/fs/nilfs2/alloc.c
+++ b/fs/nilfs2/alloc.c
@@ -205,7 +205,8 @@ static int nilfs_palloc_get_block(struct inode *inode, unsigned long blkoff,
        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);

diff --git a/fs/nilfs2/inode.c b/fs/nilfs2/inode.c
index a8ce522ac747931575104447288cdbe2ed317d0f..5c9154c2967818deafbd311228e922f57f41dc14 100644 (file)
--- a/fs/nilfs2/inode.c
+++ b/fs/nilfs2/inode.c
@@ -1025,7 +1025,7 @@ int nilfs_load_inode_block(struct inode *inode, struct buffer_head **pbh)
        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 *inode, struct buffer_head **pbh)
                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;
                }