On 2024/8/27 6:49, Paul Moore wrote:

On Mon, Aug 26, 2024 at 8:05 AM Kaixiong Yu [off-list ref] wrote:

quoted

The dac_mmap_min_addr belongs to min_addr.c, move it into
its own file from /kernel/sysctl.c. In the previous Linux kernel
boot process, sysctl_init_bases needs to be executed before
init_mmap_min_addr, So, register_sysctl_init should be executed
before update_mmap_min_addr in init_mmap_min_addr.

Signed-off-by: Kaixiong Yu <redacted>
---
  kernel/sysctl.c     |  9 ---------
  security/min_addr.c | 11 +++++++++++
  2 files changed, 11 insertions(+), 9 deletions(-)

diff --git a/kernel/sysctl.c b/kernel/sysctl.c
index 41d4afc978e6..0c0bab3dad7d 100644
--- a/kernel/sysctl.c
+++ b/kernel/sysctl.c

@@ -2059,15 +2059,6 @@ static struct ctl_table vm_table[] = {
                 .proc_handler   = proc_dointvec_minmax,
                 .extra1         = SYSCTL_ZERO,
         },
-#ifdef CONFIG_MMU
-       {
-               .procname       = "mmap_min_addr",
-               .data           = &dac_mmap_min_addr,
-               .maxlen         = sizeof(unsigned long),
-               .mode           = 0644,
-               .proc_handler   = mmap_min_addr_handler,
-       },
-#endif
  #if (defined(CONFIG_X86_32) && !defined(CONFIG_UML))|| \
     (defined(CONFIG_SUPERH) && defined(CONFIG_VSYSCALL))
         {

diff --git a/security/min_addr.c b/security/min_addr.c
index 0ce267c041ab..b2f61649e110 100644
--- a/security/min_addr.c
+++ b/security/min_addr.c

@@ -44,8 +44,19 @@ int mmap_min_addr_handler(const struct ctl_table *table, int write,
         return ret;
  }

+static struct ctl_table min_addr_sysctl_table[] = {
+       {
+               .procname       = "mmap_min_addr",
+               .data           = &dac_mmap_min_addr,
+               .maxlen         = sizeof(unsigned long),
+               .mode           = 0644,
+               .proc_handler   = mmap_min_addr_handler,
+       },
+};

I haven't chased all of the Kconfig deps to see if there is a problem,
but please provide a quick explanation in the commit description about
why it is okay to drop the CONFIG_MMU check.

According to the compilation condition in security/Makefile:

               obj-$(CONFIG_MMU)            += min_addr.o

if CONFIG_MMU is not defined, min_addr.c would not be included in the 
compilation process.
So，it is okay to drop the CONFIG_MMU check.

quoted

  static int __init init_mmap_min_addr(void)
  {
+       register_sysctl_init("vm", min_addr_sysctl_table);
         update_mmap_min_addr();

         return 0;
--
2.25.1