[PATCH] erofs-utils: tar: fix multi-chunk metadata reads

[Ajay Rajera]

Tested-by: Ajay Rajera <newajay.11r at gmail.com>
(Tested with long PAX headers via mkfs.erofs --tar)

On Thu, 26 Mar 2026 at 16:03, Vansh Choudhary <ch at vnsh.in> wrote:
>
> Advance the destination buffer in erofs_iostream_bread() after each
> erofs_iostream_read() call.
>
> Without that, metadata reads that span multiple stream chunks keep
> overwriting the start of the output buffer, which can corrupt PAX
> headers, GNU long names, long links, and other buffered metadata.
>
> Signed-off-by: Vansh Choudhary <ch at vnsh.in>
> ---
>  lib/tar.c | 4 +++-
>  1 file changed, 3 insertions(+), 1 deletion(-)
>
> diff --git a/lib/tar.c b/lib/tar.c
> index 70bf091..77754fd 100644
> --- a/lib/tar.c
> +++ b/lib/tar.c
> @@ -250,6 +250,7 @@ int erofs_iostream_read(struct erofs_iostream *ios, void **buf, u64 bytes)
>  int erofs_iostream_bread(struct erofs_iostream *ios, void *buf, u64 bytes)
>  {
>         u64 rem = bytes;
> +       u8 *dst = buf;
>         void *src;
>         int ret;
>
> @@ -257,7 +258,8 @@ int erofs_iostream_bread(struct erofs_iostream *ios, void *buf, u64 bytes)
>                 ret = erofs_iostream_read(ios, &src, rem);
>                 if (ret < 0)
>                         return ret;
> -               memcpy(buf, src, ret);
> +               memcpy(dst, src, ret);
> +               dst += ret;
>                 rem -= ret;
>         } while (rem && ret);
>
> --
> 2.43.0
>
>