bcachefs: Fix null-ptr-deref in bch2_fs_alloc()

There is a null-ptr-deref issue reported by kasan:

  KASAN: null-ptr-deref in range [0x0000000000000000-0x0000000000000007]
  Call Trace:
    <TASK>
    bch2_fs_alloc+0x1092/0x2170 [bcachefs]
    bch2_fs_open+0x683/0xe10 [bcachefs]
    ...

When initializing the name of bch_fs, it needs to dynamically alloc memory
to meet the length of the name. However, when name allocation failed, it
will cause a null-ptr-deref access exception in subsequent string copy.

Fix this issue by checking if name allocation is successful.

Fixes: 401ec4db6308 ("bcachefs: Printbuf rework")
Signed-off-by: Li Zetao <lizetao1@huawei.com>
Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>

diff --git a/fs/bcachefs/super.c b/fs/bcachefs/super.c
index 6b23e11825e6d47ef46c7f294add46fa455e6a8f..24fa41bbe7e36c3dcd024dcb56b7815e05d7a9d6 100644 (file)
--- a/fs/bcachefs/super.c
+++ b/fs/bcachefs/super.c
@@ -818,13 +818,13 @@ static struct bch_fs *bch2_fs_alloc(struct bch_sb *sb, struct bch_opts opts)
                goto err;
 
        pr_uuid(&name, c->sb.user_uuid.b);
-       strscpy(c->name, name.buf, sizeof(c->name));
-       printbuf_exit(&name);
-
        ret = name.allocation_failure ? -BCH_ERR_ENOMEM_fs_name_alloc : 0;
        if (ret)
                goto err;
 
+       strscpy(c->name, name.buf, sizeof(c->name));
+       printbuf_exit(&name);
+
        /* Compat: */
        if (le16_to_cpu(sb->version) <= bcachefs_metadata_version_inode_v2 &&
            !BCH_SB_JOURNAL_FLUSH_DELAY(sb))