seccomp: don't block getters for resource control syscalls

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
Reviewed-by: Dr. David Alan Gilbert <dgilbert@redhat.com>
Acked-by: Eduardo Otubo <otubo@redhat.com>
Signed-off-by: Daniel P. Berrangé <berrange@redhat.com>

diff --git a/softmmu/qemu-seccomp.c b/softmmu/qemu-seccomp.c
index 9c29d9cf007e8da9bf186858d88984510218c5d3..f50026778cf27c53b7e74fe668f891cd80e1b783 100644 (file)
--- 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