This is a note to let you know that I've just added the patch titled
mm/memfd: sysctl: fix MEMFD_NOEXEC_SCOPE_NOEXEC_ENFORCED
to the 6.4-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
mm-memfd-sysctl-fix-memfd_noexec_scope_noexec_enforc.patch
and it can be found in the queue-6.4 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
commit e025051cb633fd808319a2108edcb85aa5f34bb0
Author: Jeff Xu <jeffxu@xxxxxxxxxx>
Date: Wed Jul 5 06:33:14 2023 +0000
mm/memfd: sysctl: fix MEMFD_NOEXEC_SCOPE_NOEXEC_ENFORCED
[ Upstream commit 72de259130229412ca49871e70ffaf17dc9fba98 ]
Patch series "mm/memfd: fix sysctl MEMFD_NOEXEC_SCOPE_NOEXEC_ENFORCED", v2.
When sysctl vm.memfd_noexec is 2 (MEMFD_NOEXEC_SCOPE_NOEXEC_ENFORCED),
memfd_create(.., MFD_EXEC) should fail.
This complies with how MEMFD_NOEXEC_SCOPE_NOEXEC_ENFORCED is defined -
"memfd_create() without MFD_NOEXEC_SEAL will be rejected"
Thanks to Dominique Martinet <asmadeus@xxxxxxxxxxxxx> who reported the bug.
see [1] for context.
[1] https://lore.kernel.org/linux-mm/CABi2SkXUX_QqTQ10Yx9bBUGpN1wByOi_=gZU6WEy5a8MaQY3Jw@xxxxxxxxxxxxxx/T/
This patch (of 2):
When vm.memfd_noexec is 2 (MEMFD_NOEXEC_SCOPE_NOEXEC_ENFORCED),
memfd_create(.., MFD_EXEC) should fail.
This complies with how MEMFD_NOEXEC_SCOPE_NOEXEC_ENFORCED is
defined - "memfd_create() without MFD_NOEXEC_SEAL will be rejected"
Link: https://lkml.kernel.org/r/20230705063315.3680666-1-jeffxu@xxxxxxxxxx
Link: https://lkml.kernel.org/r/20230705063315.3680666-2-jeffxu@xxxxxxxxxx
Fixes: 105ff5339f49 ("mm/memfd: add MFD_NOEXEC_SEAL and MFD_EXEC")
Reported-by: Dominique Martinet <asmadeus@xxxxxxxxxxxxx>
Closes: https://lore.kernel.org/linux-mm/CABi2SkXUX_QqTQ10Yx9bBUGpN1wByOi_=gZU6WEy5a8MaQY3Jw@xxxxxxxxxxxxxx/T/
Reported-by: kernel test robot <lkp@xxxxxxxxx>
Closes: https://lore.kernel.org/oe-kbuild-all/202306301351.kkbSegQW-lkp@xxxxxxxxx/
Signed-off-by: Jeff Xu <jeffxu@xxxxxxxxxx>
Cc: Daniel Verkamp <dverkamp@xxxxxxxxxxxx>
Cc: Dmitry Torokhov <dmitry.torokhov@xxxxxxxxx>
Cc: Hugh Dickins <hughd@xxxxxxxxxx>
Cc: Jann Horn <jannh@xxxxxxxxxx>
Cc: Jorge Lucangeli Obes <jorgelo@xxxxxxxxxxxx>
Cc: Kees Cook <keescook@xxxxxxxxxxxx>
Cc: Shuah Khan <skhan@xxxxxxxxxxxxxxxxxxx>
Cc: Mike Kravetz <mike.kravetz@xxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
Stable-dep-of: 202e14222fad ("memfd: do not -EACCES old memfd_create() users with vm.memfd_noexec=2")
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
diff --git a/mm/memfd.c b/mm/memfd.c
index e763e76f11064..0bdbd2335af75 100644
--- a/mm/memfd.c
+++ b/mm/memfd.c
@@ -268,6 +268,36 @@ long memfd_fcntl(struct file *file, unsigned int cmd, unsigned int arg)
#define MFD_ALL_FLAGS (MFD_CLOEXEC | MFD_ALLOW_SEALING | MFD_HUGETLB | MFD_NOEXEC_SEAL | MFD_EXEC)
+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;
+
+ if (!(*flags & (MFD_EXEC | MFD_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));
+
+ return -EACCES;
+ }
+#endif
+
+ return 0;
+}
+
SYSCALL_DEFINE2(memfd_create,
const char __user *, uname,
unsigned int, flags)
@@ -294,35 +324,14 @@ SYSCALL_DEFINE2(memfd_create,
return -EINVAL;
if (!(flags & (MFD_EXEC | MFD_NOEXEC_SEAL))) {
-#ifdef CONFIG_SYSCTL
- int sysctl = MEMFD_NOEXEC_SCOPE_EXEC;
- struct pid_namespace *ns;
-
- ns = task_active_pid_ns(current);
- if (ns)
- sysctl = ns->memfd_noexec_scope;
-
- switch (sysctl) {
- case MEMFD_NOEXEC_SCOPE_EXEC:
- flags |= MFD_EXEC;
- break;
- case MEMFD_NOEXEC_SCOPE_NOEXEC_SEAL:
- flags |= MFD_NOEXEC_SEAL;
- break;
- default:
- pr_warn_once(
- "memfd_create(): MFD_NOEXEC_SEAL is enforced, pid=%d '%s'\n",
- task_pid_nr(current), get_task_comm(comm, current));
- return -EINVAL;
- }
-#else
- flags |= MFD_EXEC;
-#endif
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));
}
+ if (check_sysctl_memfd_noexec(&flags) < 0)
+ return -EACCES;
+
/* length includes terminating zero */
len = strnlen_user(uname, MFD_NAME_MAX_LEN + 1);
if (len <= 0)
