On Mon, 14. Aug 18:40, Aleksa Sarai wrote: > In order to incentivise userspace to switch to passing MFD_EXEC and > MFD_NOEXEC_SEAL, we need to provide a warning on each attempt to call > memfd_create() without the new flags. pr_warn_once() is not useful > because on most systems the one warning is burned up during the boot > process (on my system, systemd does this within the first second of > boot) and thus userspace will in practice never see the warnings to push > them to switch to the new flags. > > The original patchset[1] used pr_warn_ratelimited(), however there were > concerns about the degree of spam in the kernel log[2,3]. The resulting > inability to detect every case was flagged as an issue at the time[4]. > > While we could come up with an alternative rate-limiting scheme such as > only outputting the message if vm.memfd_noexec has been modified, or > only outputting the message once for a given task, these alternatives > have downsides that don't make sense given how low-stakes a single > kernel warning message is. Switching to pr_info_ratelimited() instead > should be fine -- it's possible some monitoring tool will be unhappy > with a stream of warning-level messages but there's already plenty of > info-level message spam in dmesg. > > [1]: https://lore.kernel.org/20221215001205.51969-4-jeffxu@xxxxxxxxxx/ > [2]: https://lore.kernel.org/202212161233.85C9783FB@keescook/ > [3]: https://lore.kernel.org/Y5yS8wCnuYGLHMj4@x1n/ > [4]: https://lore.kernel.org/f185bb42-b29c-977e-312e-3349eea15383@xxxxxxxxxxxxxxxxxxx/ > > Cc: stable@xxxxxxxxxxxxxxx # v6.3+ > Fixes: 105ff5339f49 ("mm/memfd: add MFD_NOEXEC_SEAL and MFD_EXEC") > Signed-off-by: Aleksa Sarai <cyphar@xxxxxxxxxx> > --- > mm/memfd.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/mm/memfd.c b/mm/memfd.c > index d65485c762de..aa46521057ab 100644 > --- a/mm/memfd.c > +++ b/mm/memfd.c > @@ -315,7 +315,7 @@ SYSCALL_DEFINE2(memfd_create, > return -EINVAL; > > if (!(flags & (MFD_EXEC | MFD_NOEXEC_SEAL))) { > - pr_warn_once( > + pr_info_ratelimited( > "%s[%d]: memfd_create() called without MFD_EXEC or MFD_NOEXEC_SEAL set\n", > current->comm, task_pid_nr(current)); > } > > -- > 2.41.0 > Hello Sarai, i got a lot of messages in dmesg with this. DMESG is unuseable with this. [ 1390.349462] __do_sys_memfd_create: 5 callbacks suppressed [ 1390.349468] pipewire-pulse[2930]: memfd_create() called without MFD_EXEC or MFD_NOEXEC_SEAL set [ 1390.350106] pipewire[2712]: memfd_create() called without MFD_EXEC or MFD_NOEXEC_SEAL set [ 1390.350366] pipewire[2712]: memfd_create() called without MFD_EXEC or MFD_NOEXEC_SEAL set [ 1390.359390] pipewire[2712]: memfd_create() called without MFD_EXEC or MFD_NOEXEC_SEAL set [ 1390.359453] pipewire[2712]: memfd_create() called without MFD_EXEC or MFD_NOEXEC_SEAL set [ 1390.848813] pipewire-pulse[2930]: memfd_create() called without MFD_EXEC or MFD_NOEXEC_SEAL set [ 1390.849425] pipewire[2712]: memfd_create() called without MFD_EXEC or MFD_NOEXEC_SEAL set [ 1390.849673] pipewire[2712]: memfd_create() called without MFD_EXEC or MFD_NOEXEC_SEAL set [ 1390.857629] pipewire[2712]: memfd_create() called without MFD_EXEC or MFD_NOEXEC_SEAL set [ 1390.857674] pipewire[2712]: memfd_create() called without MFD_EXEC or MFD_NOEXEC_SEAL set [ 1404.819637] __do_sys_memfd_create: 105 callbacks suppressed [ 1404.819641] pipewire-pulse[2930]: memfd_create() called without MFD_EXEC or MFD_NOEXEC_SEAL set [ 1404.819950] pipewire[2712]: memfd_create() called without MFD_EXEC or MFD_NOEXEC_SEAL set [ 1404.820054] pipewire[2712]: memfd_create() called without MFD_EXEC or MFD_NOEXEC_SEAL set [ 1404.824240] pipewire[2712]: memfd_create() called without MFD_EXEC or MFD_NOEXEC_SEAL set [ 1404.824279] pipewire[2712]: memfd_create() called without MFD_EXEC or MFD_NOEXEC_SEAL set [ 1430.373186] pipewire-pulse[2930]: memfd_create() called without MFD_EXEC or MFD_NOEXEC_SEAL set [ 1430.373906] pipewire[2712]: memfd_create() called without MFD_EXEC or MFD_NOEXEC_SEAL set [ 1430.374131] pipewire[2712]: memfd_create() called without MFD_EXEC or MFD_NOEXEC_SEAL set [ 1430.382397] pipewire[2712]: memfd_create() called without MFD_EXEC or MFD_NOEXEC_SEAL set [ 1430.382485] pipewire[2712]: memfd_create() called without MFD_EXEC or MFD_NOEXEC_SEAL set [ 1430.499581] pipewire-pulse[2930]: memfd_create() called without MFD_EXEC or MFD_NOEXEC_SEAL set [ 1430.500077] pipewire[2712]: memfd_create() called without MFD_EXEC or MFD_NOEXEC_SEAL set [ 1430.500265] pipewire[2712]: memfd_create() called without MFD_EXEC or MFD_NOEXEC_SEAL set [ 1430.512772] pipewire[2712]: memfd_create() called without MFD_EXEC or MFD_NOEXEC_SEAL set [ 1430.512840] pipewire[2712]: memfd_create() called without MFD_EXEC or MFD_NOEXEC_SEAL set [ 1444.388519] __do_sys_memfd_create: 60 callbacks suppressed [ 1444.388525] pipewire-pulse[2930]: memfd_create() called without MFD_EXEC or MFD_NOEXEC_SEAL set [ 1444.389061] pipewire[2712]: memfd_create() called without MFD_EXEC or MFD_NOEXEC_SEAL set [ 1444.389335] pipewire[2712]: memfd_create() called without MFD_EXEC or MFD_NOEXEC_SEAL set [ 1444.397909] pipewire[2712]: memfd_create() called without MFD_EXEC or MFD_NOEXEC_SEAL set [ 1444.397965] pipewire[2712]: memfd_create() called without MFD_EXEC or MFD_NOEXEC_SEAL set [ 1444.503514] pipewire-pulse[2930]: memfd_create() called without MFD_EXEC or MFD_NOEXEC_SEAL set [ 1444.503658] pipewire[2712]: memfd_create() called without MFD_EXEC or MFD_NOEXEC_SEAL set [ 1444.503726] pipewire[2712]: memfd_create() called without MFD_EXEC or MFD_NOEXEC_SEAL set [ 1444.507841] pipewire[2712]: memfd_create() called without MFD_EXEC or MFD_NOEXEC_SEAL set [ 1444.507870] pipewire[2712]: memfd_create() called without MFD_EXEC or MFD_NOEXEC_SEAL set [ 1449.707966] __do_sys_memfd_create: 25 callbacks suppressed Best regards Damian
