Re: [PATCH 2/3] linux-user: Fix unlock_user API usage

[Alistair Francis <alistair23@gmail.com>]

On Sat, Mar 21, 2026 at 10:50 AM Nicholas Piggin <npiggin@gmail.com> wrote:
>
> Fix errors in unlock_user() calls:
> - unlock_user() with len=1 instead of len=written
> - unlock_user() with len=1 instead of len=0
> - unlock_user() with len=0 instead of len=1

Can you explain what the errors are and why this fixes them?

At least to me (I don't know the linux-user stuff very well) I don't
understand what is being fixed here

Alistair

>
> Signed-off-by: Nicholas Piggin <npiggin@gmail.com>
> ---
>  linux-user/linuxload.c | 2 +-
>  linux-user/syscall.c   | 6 +++---
>  2 files changed, 4 insertions(+), 4 deletions(-)
>
> diff --git a/linux-user/linuxload.c b/linux-user/linuxload.c
> index 85d700953e..79416a94c9 100644
> --- a/linux-user/linuxload.c
> +++ b/linux-user/linuxload.c
> @@ -19,7 +19,7 @@ abi_long memcpy_to_target(abi_ulong dest, const void *src, unsigned long len)
>          return -TARGET_EFAULT;
>      }
>      memcpy(host_ptr, src, len);
> -    unlock_user(host_ptr, dest, 1);
> +    unlock_user(host_ptr, dest, len);
>      return 0;
>  }
>
> diff --git a/linux-user/syscall.c b/linux-user/syscall.c
> index 7832a1aba5..13b8bd9ed3 100644
> --- a/linux-user/syscall.c
> +++ b/linux-user/syscall.c
> @@ -2989,7 +2989,7 @@ get_timeout:
>              if (put_user_u32(lv, optlen)) {
>                  return -TARGET_EFAULT;
>              }
> -            unlock_user(results, optval_addr, 0);
> +            unlock_user(results, optval_addr, len);
>              break;
>          }
>  #endif /* LINUX_VERSION_CODE >= KERNEL_VERSION(4, 2, 0) */
> @@ -4006,7 +4006,7 @@ static inline abi_long host_to_target_semarray(int semid, abi_ulong target_addr,
>          __put_user((*host_array)[i], &array[i]);
>      }
>      g_free(*host_array);
> -    unlock_user(array, target_addr, 1);
> +    unlock_user(array, target_addr, nsems * sizeof(unsigned short));
>
>      return 0;
>  }
> @@ -7888,7 +7888,7 @@ static inline abi_long target_to_host_sigevent(struct sigevent *host_sevp,
>      host_sevp->sigev_notify = tswap32(target_sevp->sigev_notify);
>      host_sevp->sigev_notify_thread_id = tswap32(target_sevp->_sigev_un._tid);
>
> -    unlock_user_struct(target_sevp, target_addr, 1);
> +    unlock_user_struct(target_sevp, target_addr, 0);
>      return 0;
>  }
>
> --
> 2.51.0
>
>