Re: [PATCH v2 1/2] bcachefs: avoid copy from NULL printbuf

[Hongbo Li]

On 2024/10/9 11:13, Kent Overstreet wrote:

On Thu, Sep 26, 2024 at 10:00:00AM GMT, Hongbo Li wrote:

printbuf.buf may be NULL if allocation_failure is true. Check
for this prior to using it as a seq_puts() source.

Fixes: fa8e94faeece ("bcachefs: Heap allocate printbufs")
Signed-off-by: David Disseldorp <dd...@suse.de>
Signed-off-by: Hongbo Li <lihongb...@huawei.com>

Let's do this by adding a proper printbuf_err() helper - have it return
-ENOMEM on allocation failure, and do a normal
if (ret)
        goto err;

so it looks more standard.

---
  fs/bcachefs/fs.c | 7 +++++--
  1 file changed, 5 insertions(+), 2 deletions(-)

diff --git a/fs/bcachefs/fs.c b/fs/bcachefs/fs.c
index e774cb3e6b1a..d6e26b5056f3 100644
--- a/fs/bcachefs/fs.c
+++ b/fs/bcachefs/fs.c
@@ -1923,13 +1923,16 @@ static int bch2_show_options(struct seq_file *seq, 
struct dentry *root)
  {
        struct bch_fs *c = root->d_sb->s_fs_info;
        struct printbuf buf = PRINTBUF;
+       int ret = 0;

bch2_opts_to_text(&buf, c->opts, c, c->disk_sb.sb,

                          OPT_MOUNT, OPT_HIDDEN, OPT_SHOW_MOUNT_STYLE);
        printbuf_nul_terminate(&buf);
-       seq_puts(seq, buf.buf);

like this?:
        ret = printbuf_err(buf);
        if (ret)
            goto err:
        seq_printf(seq, ",%s", buf.buf);
        printbuf_exit(&buf);

err:
        return ret;


Thanks,
Hongbo

+       if (buf.allocation_failure)
+               ret = -ENOMEM;
+       else
+               seq_puts(seq, buf.buf);

- int ret = buf.allocation_failure ? -ENOMEM : 0;

        printbuf_exit(&buf);
        return ret;
  }
--
2.34.1