From 1e21c2de3878d61ecc14bcb2f9290c34fe2e5fc0 Mon Sep 17 00:00:00 2001
From: Ryusuke Konishi <konishi.ryusuke@gmail.com>
Date: Sun, 23 Jun 2024 14:11:34 +0900
Subject: [PATCH] nilfs2: add missing check for inode numbers on directory
entries
commit bb76c6c274683c8570ad788f79d4b875bde0e458 upstream.
Syzbot reported that mounting and unmounting a specific pattern of
corrupted nilfs2 filesystem images causes a use-after-free of metadata
file inodes, which triggers a kernel bug in lru_add_fn().
As Jan Kara pointed out, this is because the link count of a metadata file
gets corrupted to 0, and nilfs_evict_inode(), which is called from iput(),
tries to delete that inode (ifile inode in this case).
The inconsistency occurs because directories containing the inode numbers
of these metadata files that should not be visible in the namespace are
read without checking.
Fix this issue by treating the inode numbers of these internal files as
errors in the sanity check helper when reading directory folios/pages.
Also thanks to Hillf Danton and Matthew Wilcox for their initial mm-layer
analysis.
Link: https://lkml.kernel.org/r/20240623051135.4180-3-konishi.ryusuke@gmail.com
Signed-off-by: Ryusuke Konishi <konishi.ryusuke@gmail.com>
Reported-by: syzbot+d79afb004be235636ee8@syzkaller.appspotmail.com
Closes: https://syzkaller.appspot.com/bug?extid=d79afb004be235636ee8
Reported-by: Jan Kara <jack@suse.cz>
Closes: https://lkml.kernel.org/r/20240617075758.wewhukbrjod5fp5o@quack3
Tested-by: Ryusuke Konishi <konishi.ryusuke@gmail.com>
Cc: Hillf Danton <hdanton@sina.com>
Cc: Matthew Wilcox (Oracle) <willy@infradead.org>
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 | 6 ++++++
fs/nilfs2/nilfs.h | 5 +++++
2 files changed, 11 insertions(+)
diff --git a/fs/nilfs2/dir.c b/fs/nilfs2/dir.c
index e9668e455a35e..4bba1970ad333 100644
--- a/fs/nilfs2/dir.c
+++ b/fs/nilfs2/dir.c
@@ -143,6 +143,9 @@ static bool nilfs_check_page(struct page *page)
goto Enamelen;
if (((offs + rec_len - 1) ^ offs) & ~(chunk_size-1))
goto Espan;
+ if (unlikely(p->inode &&
+ NILFS_PRIVATE_INODE(le64_to_cpu(p->inode))))
+ goto Einumber;
}
if (offs != limit)
goto Eend;
@@ -168,6 +171,9 @@ static bool nilfs_check_page(struct page *page)
goto bad_entry;
Espan:
error = "directory entry across blocks";
+ goto bad_entry;
+Einumber:
+ error = "disallowed inode number";
bad_entry:
nilfs_error(sb,
"bad entry in directory #%lu: %s - offset=%lu, inode=%lu, rec_len=%d, name_len=%d",
diff --git a/fs/nilfs2/nilfs.h b/fs/nilfs2/nilfs.h
index d12073e5410ed..a1ff52265e1b0 100644
--- a/fs/nilfs2/nilfs.h
+++ b/fs/nilfs2/nilfs.h
@@ -121,6 +121,11 @@ enum {
((ino) >= NILFS_FIRST_INO(sb) || \
((ino) < NILFS_USER_INO && (NILFS_SYS_INO_BITS & BIT(ino))))
+#define NILFS_PRIVATE_INODE(ino) ({ \
+ ino_t __ino = (ino); \
+ ((__ino) < NILFS_USER_INO && (__ino) != NILFS_ROOT_INO && \
+ (__ino) != NILFS_SKETCH_INO); })
+
/**
* struct nilfs_transaction_info: context information for synchronization
* @ti_magic: Magic number
--
GitLab