Re: [PATCH] seccomp: don't block getters for resource control syscalls

["Dr. David Alan Gilbert" <dgilbert@redhat.com>]

* Daniel P. Berrangé (berrange@redhat.com) wrote:
> Recent GLibC calls sched_getaffinity in code paths related to malloc and
> when QEMU blocks access, it sends it off into a bad codepath resulting
> in stack exhaustion[1]. The GLibC bug is being fixed[2], but none the
> less, GLibC has valid reasons to want to use sched_getaffinity.
> 
> It is not unreasonable for code to want to run many resource syscalls
> for information gathering, so it is a bit too harsh for QEMU to block
> them.
> 
> [1] https://bugzilla.redhat.com/show_bug.cgi?id=1975693
> [2] https://sourceware.org/pipermail/libc-alpha/2021-June/128271.html
> Signed-off-by: Daniel P. Berrangé <berrange@redhat.com>

Reviewed-by: Dr. David Alan Gilbert <dgilbert@redhat.com>

> ---
>  softmmu/qemu-seccomp.c | 6 ------
>  1 file changed, 6 deletions(-)
> 
> diff --git a/softmmu/qemu-seccomp.c b/softmmu/qemu-seccomp.c
> index 9c29d9cf00..f50026778c 100644
> --- a/softmmu/qemu-seccomp.c
> +++ b/softmmu/qemu-seccomp.c
> @@ -97,17 +97,11 @@ static const struct QemuSeccompSyscall denylist[] = {
>      { SCMP_SYS(vfork),                  QEMU_SECCOMP_SET_SPAWN },
>      { SCMP_SYS(execve),                 QEMU_SECCOMP_SET_SPAWN },
>      /* resource control */
> -    { SCMP_SYS(getpriority),            QEMU_SECCOMP_SET_RESOURCECTL },
>      { SCMP_SYS(setpriority),            QEMU_SECCOMP_SET_RESOURCECTL },
>      { SCMP_SYS(sched_setparam),         QEMU_SECCOMP_SET_RESOURCECTL },
> -    { SCMP_SYS(sched_getparam),         QEMU_SECCOMP_SET_RESOURCECTL },
>      { SCMP_SYS(sched_setscheduler),     QEMU_SECCOMP_SET_RESOURCECTL,
>        ARRAY_SIZE(sched_setscheduler_arg), sched_setscheduler_arg },
> -    { SCMP_SYS(sched_getscheduler),     QEMU_SECCOMP_SET_RESOURCECTL },
>      { SCMP_SYS(sched_setaffinity),      QEMU_SECCOMP_SET_RESOURCECTL },
> -    { SCMP_SYS(sched_getaffinity),      QEMU_SECCOMP_SET_RESOURCECTL },
> -    { SCMP_SYS(sched_get_priority_max), QEMU_SECCOMP_SET_RESOURCECTL },
> -    { SCMP_SYS(sched_get_priority_min), QEMU_SECCOMP_SET_RESOURCECTL },
>  };
>  
>  static inline __attribute__((unused)) int
> -- 
> 2.31.1
> 
-- 
Dr. David Alan Gilbert / dgilbert@redhat.com / Manchester, UK