On 24 November 2016 at 16:08, Lena Djokic <lena.djo...@rt-rk.com> wrote:
> Third argument represents lenght not second.
typo: "length"
> If second argument is NULL it should be passed without
> using lock_user function which would, in that case, return
> EFAULT, and system call supports passing NULL as second argument.
Looking at the kernel code, it doesn't support NULL as the
second argument for the three actions here (READ, READ_CLEAR,
READ_ALL) -- they all fail EINVAL. So what we're doing here
is just returning a better errno. I think we can do
this more simply by just changing the current
if (len < 0) {
goto fail;
}
to "if (!arg2 || len < 0) {" (which is what the kernel code does).
(I think it would also be reasonable to consistently use "len"
and never "arg3" (the existing code has an odd mix of both);
if you want to do that cleanup you could add an extra patch for
it, but you don't have to.)
> Signed-off-by: Lena Djokic <lena.djo...@rt-rk.com>
> ---
> linux-user/syscall.c | 16 ++++++++--------
> 1 file changed, 8 insertions(+), 8 deletions(-)
>
> diff --git a/linux-user/syscall.c b/linux-user/syscall.c
> index 61c4126..3faf4f0 100644
> --- a/linux-user/syscall.c
> +++ b/linux-user/syscall.c
> @@ -9426,7 +9426,7 @@ abi_long do_syscall(void *cpu_env, int num, abi_long
> arg1,
> #if defined(TARGET_NR_syslog)
> case TARGET_NR_syslog:
> {
> - int len = arg2;
> + int len = arg3;
>
> switch (arg1) {
> case TARGET_SYSLOG_ACTION_CLOSE: /* Close log */
> @@ -9450,13 +9450,13 @@ abi_long do_syscall(void *cpu_env, int num, abi_long
> arg1,
> goto fail;
> }
> ret = 0;
> - if (len == 0) {
> - break;
> - }
> - p = lock_user(VERIFY_WRITE, arg2, arg3, 0);
> - if (!p) {
> - ret = -TARGET_EFAULT;
> - goto fail;
> + p = NULL;
> + if (arg2) {
> + p = lock_user(VERIFY_WRITE, arg2, arg3, 0);
> + if (!p) {
> + ret = -TARGET_EFAULT;
> + goto fail;
> + }
> }
> ret = get_errno(sys_syslog((int)arg1, p, (int)arg3));
> unlock_user(p, arg2, arg3);
> --
> 2.7.4
thanks
-- PMM
