FAILED: patch "[PATCH] memfd: do not -EACCES old memfd_create() users with" failed to apply to 6.4-stable tree
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[email protected]
maintainerThe 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 <[email protected]>.
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 202e14222fadb246dfdf182e67de1518e86a1e20
# <resolve conflicts, build, test, etc.>
git commit -s
git send-email --to '<[email protected]>' --in-reply-to '2023090747-scant-detest-aeed@gregkh' --subject-prefix 'PATCH 6.4.y' HEAD^..
Possible dependencies:
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 202e14222fadb246dfdf182e67de1518e86a1e20 Mon Sep 17 00:00:00 2001
From: Aleksa Sarai <[email protected]>
Date: Mon, 14 Aug 2023 18:40:58 +1000
Subject: [PATCH] memfd: do not -EACCES old memfd_create() users with
vm.memfd_noexec=2
Given the difficulty of auditing all of userspace to figure out whether every memfd_create() user has switched to passing MFD_EXEC and MFD_NOEXEC_SEAL flags, it seems far less distruptive to make it possible for older programs that don't make use of executable memfds to run under vm.memfd_noexec=2. Otherwise, a small dependency change can result in spurious errors. For programs that don't use executable memfds, passing MFD_NOEXEC_SEAL is functionally a no-op and thus having the same
In addition, every failure under vm.memfd_noexec=2 needs to print to the kernel log so that userspace can figure out where the error came from. The concerns about pr_warn_ratelimited() spam that caused the switch to pr_warn_once()[1,2] do not apply to the vm.memfd_noexec=2 case.
This is a user-visible API change, but as it allows programs to do something that would be blocked before, and the sysctl itself was broken and recently released, it seems unlikely this will cause any issues.
[1]: https://lore.kernel.org/Y5yS8wCnuYGLHMj4@x1n/
[2]: https://lore.kernel.org/202212161233.85C9783FB@keescook/
include/linux/pid_namespace.h +4 -12
@@ -17,18 +17,10 @@struct fs_pin ;#if defined(CONFIG_SYSCTL ) && defined(CONFIG_MEMFD_CREATE ) -/* -* sysctl for vm.memfd_noexec -* 0: memfd_create() without MFD_EXEC nor MFD_NOEXEC_SEAL -* acts like MFD_EXEC was set. -* 1: memfd_create() without MFD_EXEC nor MFD_NOEXEC_SEAL -* acts like MFD_NOEXEC_SEAL was set. -* 2: memfd_create() without MFD_NOEXEC_SEAL will be -* rejected. -*/ -#define MEMFD_NOEXEC_SCOPE_EXEC 0 -#define MEMFD_NOEXEC_SCOPE_NOEXEC_SEAL 1 -#define MEMFD_NOEXEC_SCOPE_NOEXEC_ENFORCED 2 +/* modes for vm.memfd_noexec sysctl */ +#define MEMFD_NOEXEC_SCOPE_EXEC 0/* MFD_EXEC implied if unset */ +#define MEMFD_NOEXEC_SCOPE_NOEXEC_SEAL 1/* MFD_NOEXEC_SEAL implied if unset */ +#define MEMFD_NOEXEC_SCOPE_NOEXEC_ENFORCED 2/* same as 1, except MFD_EXEC rejected */ #endif struct pid_namespace {
mm/memfd.c +11 -19
@@ -271,30 +271,22 @@ long memfd_fcntl(struct file *file, unsigned int cmd, unsigned int arg)static int check_sysctl_memfd_noexec (unsigned int *flags) {#ifdef CONFIG_SYSCTL -char comm[TASK_COMM_LEN ]; -int sysctl =MEMFD_NOEXEC_SCOPE_EXEC ; -struct pid_namespace *ns; - - ns =task_active_pid_ns (current); -if (ns) - sysctl = ns->memfd_noexec_scope; +int sysctl =task_active_pid_ns (current)->memfd_noexec_scope;if (!(*flags & (MFD_EXEC |MFD_NOEXEC_SEAL ))) { -if (sysctl ==MEMFD_NOEXEC_SCOPE_NOEXEC_SEAL ) +if (sysctl >=MEMFD_NOEXEC_SCOPE_NOEXEC_SEAL ) *flags |=MFD_NOEXEC_SEAL ;else *flags |=MFD_EXEC ; } -if (*flags &MFD_EXEC && sysctl >=MEMFD_NOEXEC_SCOPE_NOEXEC_ENFORCED ) { -pr_warn_once ( -"memfd_create(): MFD_NOEXEC_SEAL is enforced, pid=%d '%s'\n" , -task_pid_nr (current),get_task_comm (comm, current)); - +if (!(*flags &MFD_NOEXEC_SEAL ) && sysctl >=MEMFD_NOEXEC_SCOPE_NOEXEC_ENFORCED ) { +pr_err_ratelimited ( +"%s[%d]: memfd_create() requires MFD_NOEXEC_SEAL with vm.memfd_noexec=%d\n" , + current->comm,task_pid_nr (current), sysctl);return -EACCES ; }#endif -return 0 ; }
@@ -302,7 +294,6 @@ SYSCALL_DEFINE2(memfd_create, const char __user *, uname, unsigned int, flags) { - char comm[TASK_COMM_LEN]; unsigned int *file_seals;struct file *file;int fd, error;
@@ -325,12 +316,13 @@ SYSCALL_DEFINE2(memfd_create,if (!(flags & (MFD_EXEC |MFD_NOEXEC_SEAL ))) {pr_warn_once ( -"memfd_create() without MFD_EXEC nor MFD_NOEXEC_SEAL, pid=%d '%s'\n" , -task_pid_nr (current),get_task_comm (comm, current)); +"%s[%d]: memfd_create() called without MFD_EXEC or MFD_NOEXEC_SEAL set\n" , + current->comm,task_pid_nr (current)); } -if (check_sysctl_memfd_noexec (&flags) <0 ) -return -EACCES ; + error =check_sysctl_memfd_noexec (&flags); +if (error <0 ) +return error;/* length includes terminating zero */ len =strnlen_user (uname,MFD_NAME_MAX_LEN +1 );
tools/testing/selftests/memfd/memfd_test.c +17 -5
@@ -1145,11 +1145,23 @@ static void test_sysctl_child(void)printf ("%s sysctl 2\n" , memfd_str);sysctl_assert_write ("2" ); -mfd_fail_new ("kern_memfd_sysctl_2" , -MFD_CLOEXEC |MFD_ALLOW_SEALING ); -mfd_fail_new ("kern_memfd_sysctl_2_MFD_EXEC" , -MFD_CLOEXEC |MFD_EXEC ); - fd =mfd_assert_new ("" ,0 ,MFD_NOEXEC_SEAL ); +mfd_fail_new ("kern_memfd_sysctl_2_exec" , +MFD_EXEC |MFD_CLOEXEC |MFD_ALLOW_SEALING ); + + fd =mfd_assert_new ("kern_memfd_sysctl_2_dfl" , + mfd_def_size, +MFD_CLOEXEC |MFD_ALLOW_SEALING ); +mfd_assert_mode (fd,0666 ); +mfd_assert_has_seals (fd,F_SEAL_EXEC ); +mfd_fail_chmod (fd,0777 ); +close (fd); + + fd =mfd_assert_new ("kern_memfd_sysctl_2_noexec_seal" , + mfd_def_size, +MFD_NOEXEC_SEAL |MFD_CLOEXEC |MFD_ALLOW_SEALING ); +mfd_assert_mode (fd,0666 ); +mfd_assert_has_seals (fd,F_SEAL_EXEC ); +mfd_fail_chmod (fd,0777 );close (fd);sysctl_fail_write ("0" );