Fix regression due to "fs: move binfmt_misc sysctl to its own file"

Commit fc3b58422b84 ("fs: move binfmt_misc sysctl to its own file") did
not go unnoticed, binfmt-support stopped to work on my Debian system
since v5.17-rc2 (did not check with -rc1).

The existance of the /proc/sys/fs/binfmt_misc is a precondition for
attempting to mount the binfmt_misc fs, which in turn triggers the
autoload of the binfmt_misc module.  Without it, no module is loaded and
no binfmt is available at boot.

Building as built-in or manually loading the module and mounting the fs
works fine, it's therefore only a matter of interaction with user-space.
I could try to improve the Debian systemd configuration but I can't say
anything about the other distributions.

This patch restores a working system right after boot.

Fixes: fc3b58422b84 ("fs: move binfmt_misc sysctl to its own file")
Signed-off-by: Domenico Andreoli <domenico.andreoli@linux.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Luis Chamberlain <mcgrof@kernel.org>
Reviewed-by: Tong Zhang <ztong0001@gmail.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/fs/binfmt_misc.c b/fs/binfmt_misc.c
index c07f35719ee3fdc893a2e17a36d31b9360ff655f..e1eae7ea823aeb2d5d0b245511658fcdb3a3ed09 100644 (file)
--- a/fs/binfmt_misc.c
+++ b/fs/binfmt_misc.c
@@ -817,20 +817,16 @@ static struct file_system_type bm_fs_type = {
 };
 MODULE_ALIAS_FS("binfmt_misc");
 
-static struct ctl_table_header *binfmt_misc_header;
-
 static int __init init_misc_binfmt(void)
 {
        int err = register_filesystem(&bm_fs_type);
        if (!err)
                insert_binfmt(&misc_format);
-       binfmt_misc_header = register_sysctl_mount_point("fs/binfmt_misc");
-       return 0;
+       return err;
 }
 
 static void __exit exit_misc_binfmt(void)
 {
-       unregister_sysctl_table(binfmt_misc_header);
        unregister_binfmt(&misc_format);
        unregister_filesystem(&bm_fs_type);
 }

diff --git a/fs/file_table.c b/fs/file_table.c
index 57edef16dce468422bd36f5a94d40e0f9d403347..4969021fa6764b3872016a63bac195ff46e6a9d5 100644 (file)
--- a/fs/file_table.c
+++ b/fs/file_table.c
@@ -119,6 +119,8 @@ static struct ctl_table fs_stat_sysctls[] = {
 static int __init init_fs_stat_sysctls(void)
 {
        register_sysctl_init("fs", fs_stat_sysctls);
+       if (IS_ENABLED(CONFIG_BINFMT_MISC))
+               register_sysctl_mount_point("fs/binfmt_misc");
        return 0;
 }
 fs_initcall(init_fs_stat_sysctls);