From 24c1c8566a9b6be51f5347be2ea76e25fc82b11e Mon Sep 17 00:00:00 2001
From: Ryusuke Konishi <konishi.ryusuke@gmail.com>
Date: Sat, 29 Jun 2024 01:51:07 +0900
Subject: [PATCH] nilfs2: fix kernel bug on rename operation of broken
directory
commit a9e1ddc09ca55746079cc479aa3eb6411f0d99d4 upstream.
Syzbot reported that in rename directory operation on broken directory on
nilfs2, __block_write_begin_int() called to prepare block write may fail
BUG_ON check for access exceeding the folio/page size.
This is because nilfs_dotdot(), which gets parent directory reference
entry ("..") of the directory to be moved or renamed, does not check
consistency enough, and may return location exceeding folio/page size for
broken directories.
Fix this issue by checking required directory entries ("." and "..") in
the first chunk of the directory in nilfs_dotdot().
Link: https://lkml.kernel.org/r/20240628165107.9006-1-konishi.ryusuke@gmail.com
Signed-off-by: Ryusuke Konishi <konishi.ryusuke@gmail.com>
Reported-by: syzbot+d3abed1ad3d367fa2627@syzkaller.appspotmail.com
Closes: https://syzkaller.appspot.com/bug?extid=d3abed1ad3d367fa2627
Fixes: 2ba466d74ed7 ("nilfs2: directory entry operations")
Tested-by: Ryusuke Konishi <konishi.ryusuke@gmail.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
fs/nilfs2/dir.c | 32 ++++++++++++++++++++++++++++++--
1 file changed, 30 insertions(+), 2 deletions(-)
diff --git a/fs/nilfs2/dir.c b/fs/nilfs2/dir.c
index 3e15a8fdac4c7..5c0e280c83eea 100644
--- a/fs/nilfs2/dir.c
+++ b/fs/nilfs2/dir.c
@@ -396,11 +396,39 @@ nilfs_find_entry(struct inode *dir, const struct qstr *qstr,
struct nilfs_dir_entry *nilfs_dotdot(struct inode *dir, struct page **p)
{
- struct nilfs_dir_entry *de = nilfs_get_page(dir, 0, p);
+ struct page *page;
+ struct nilfs_dir_entry *de, *next_de;
+ size_t limit;
+ char *msg;
+ de = nilfs_get_page(dir, 0, &page);
if (IS_ERR(de))
return NULL;
- return nilfs_next_entry(de);
+
+ limit = nilfs_last_byte(dir, 0); /* is a multiple of chunk size */
+ if (unlikely(!limit || le64_to_cpu(de->inode) != dir->i_ino ||
+ !nilfs_match(1, ".", de))) {
+ msg = "missing '.'";
+ goto fail;
+ }
+
+ next_de = nilfs_next_entry(de);
+ /*
+ * If "next_de" has not reached the end of the chunk, there is
+ * at least one more record. Check whether it matches "..".
+ */
+ if (unlikely((char *)next_de == (char *)de + nilfs_chunk_size(dir) ||
+ !nilfs_match(2, "..", next_de))) {
+ msg = "missing '..'";
+ goto fail;
+ }
+ *p = page;
+ return next_de;
+
+fail:
+ nilfs_error(dir->i_sb, "directory #%lu %s", dir->i_ino, msg);
+ nilfs_put_page(page);
+ return NULL;
}
ino_t nilfs_inode_by_name(struct inode *dir, const struct qstr *qstr)
--
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