5.4-stable review patch. If anyone has any objections, please let me know.
------------------
From: Ryusuke Konishi konishi.ryusuke@gmail.com
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(+)
--- a/fs/nilfs2/dir.c +++ b/fs/nilfs2/dir.c @@ -143,6 +143,9 @@ static bool nilfs_check_page(struct 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 @@ Enamelen: 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", --- 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