Re: [PATCH] fs/ntfs3: resize log->one_page_buf when adopting on-disk page size

[Konstantin Komarov <almaz.alexandrovich@paragon-software.com>]

On 6/5/26 06:19, Jamie Nguyen wrote:

> log_replay() allocates log->one_page_buf using the page size that was
> chosen from the host PAGE_SIZE:
>
>          log->one_page_buf = kmalloc(log->page_size, GFP_NOFS);
>
> Later, when a restart area is found, the log page size recorded on disk
> is adopted:
>
>          t32 = le32_to_cpu(log->rst_info.r_page->sys_page_size);
>          if (log->page_size != t32) {
>                  log->l_size = log->orig_file_size;
>                  log->page_size = norm_file_page(t32, &log->l_size,
>                                                  t32 == DefaultLogPageSize);
>          }
>
> If the on-disk page size is larger than the size used for the initial
> allocation, log->page_size grows but one_page_buf is left at its
> original, smaller size. A subsequent unaligned read_log_page() then
> reads log->page_size bytes into the undersized scratch buffer:
>
>          page_buf = page_off ? log->one_page_buf : *buffer;
>          err = ntfs_read_run_nb_ra(ni->mi.sbi, &ni->file.run, page_vbo, page_buf,
>                                    log->page_size, NULL, &log->read_ahead);
>
> overflowing the allocation. This is reachable when mounting a dirty
> NTFS volume whose log was formatted with a page size larger than the
> buffer initially allocated on the mounting host (for example a 64K-log
> volume mounted on a host that allocated a 4K scratch buffer).
>
> Grow one_page_buf when the adopted on-disk page size exceeds the size
> used for the initial allocation. On krealloc() failure the original
> buffer is left intact and freed by the existing error path.
>
> Fixes: b46acd6a6a627 ("fs/ntfs3: Add NTFS journal")
> Reported-by: Carol L Soto <csoto@nvidia.com>
> Signed-off-by: Jamie Nguyen <jamien@nvidia.com>
> ---
>   fs/ntfs3/fslog.c | 19 +++++++++++++++++++
>   1 file changed, 19 insertions(+)
>
> diff --git a/fs/ntfs3/fslog.c b/fs/ntfs3/fslog.c
> index 95e1cdb47..b44bcfd31 100644
> --- a/fs/ntfs3/fslog.c
> +++ b/fs/ntfs3/fslog.c
> @@ -3976,9 +3976,28 @@ int log_replay(struct ntfs_inode *ni, bool *initialized)
>           */
>          t32 = le32_to_cpu(log->rst_info.r_page->sys_page_size);
>          if (log->page_size != t32) {
> +               u32 old_page_size = log->page_size;
> +
>                  log->l_size = log->orig_file_size;
>                  log->page_size = norm_file_page(t32, &log->l_size,
>                                                  t32 == DefaultLogPageSize);
> +
> +               /*
> +                * If the adopted on-disk page size is larger than the size used
> +                * to allocate one_page_buf above, grow the scratch buffer so a
> +                * later read_log_page() cannot overflow it.
> +                */
> +               if (log->page_size > old_page_size) {
> +                       void *buf;
> +
> +                       buf = krealloc(log->one_page_buf, log->page_size,
> +                                      GFP_NOFS);
> +                       if (!buf) {
> +                               err = -ENOMEM;
> +                               goto out;
> +                       }
> +                       log->one_page_buf = buf;
> +               }
>          }
>
>          if (log->page_size != t32 ||
> --
> 2.43.0
>
Hello,

Your patch was applied, thank you.

Regards,
Konstantin