The patch below does not apply to the 6.4-stable tree. If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to stable@vger.kernel.org.
To reproduce the conflict and resubmit, you may use the following commands:
git fetch https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/ linux-6.4.y git checkout FETCH_HEAD git cherry-pick -x 434ed3350f57c03a9654fe0619755cc137a58935 # <resolve conflicts, build, test, etc.> git commit -s git send-email --to 'stable@vger.kernel.org' --in-reply-to '2023090742-velocity-perjury-fa80@gregkh' --subject-prefix 'PATCH 6.4.y' HEAD^..
Possible dependencies:
434ed3350f57 ("memfd: improve userspace warnings for missing exec-related flags") 202e14222fad ("memfd: do not -EACCES old memfd_create() users with vm.memfd_noexec=2") badbbcd76545 ("selftests/memfd: sysctl: fix MEMFD_NOEXEC_SCOPE_NOEXEC_ENFORCED") 72de25913022 ("mm/memfd: sysctl: fix MEMFD_NOEXEC_SCOPE_NOEXEC_ENFORCED")
thanks,
greg k-h
------------------ original commit in Linus's tree ------------------
From 434ed3350f57c03a9654fe0619755cc137a58935 Mon Sep 17 00:00:00 2001 From: Aleksa Sarai cyphar@cyphar.com Date: Mon, 14 Aug 2023 18:40:59 +1000 Subject: [PATCH] memfd: improve userspace warnings for missing exec-related flags
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@google.com/ [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@linuxfoundation...
Link: https://lkml.kernel.org/r/20230814-memfd-vm-noexec-uapi-fixes-v2-3-7ff9e3e10... Fixes: 105ff5339f49 ("mm/memfd: add MFD_NOEXEC_SEAL and MFD_EXEC") Signed-off-by: Aleksa Sarai cyphar@cyphar.com Cc: Christian Brauner brauner@kernel.org Cc: Daniel Verkamp dverkamp@chromium.org Cc: Dominique Martinet asmadeus@codewreck.org Cc: Kees Cook keescook@chromium.org Cc: Shuah Khan shuah@kernel.org Cc: stable@vger.kernel.org Signed-off-by: Andrew Morton akpm@linux-foundation.org
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)); }