alloc_tag: Tighten file permissions on /proc/allocinfo

The /proc/allocinfo file exposes a tremendous about of information about
kernel build details, memory allocations (obviously), and potentially even
image layout (due to ordering).  As this is intended to be consumed by
system owners (like /proc/slabinfo), use the same file permissions as
there: 0400.

Link: https://lkml.kernel.org/r/20240425200844.work.184-kees@kernel.orgSigned-off-by: Kees Cook <keescook@chromium.org>
Cc: Kent Overstreet <kent.overstreet@linux.dev>
Cc: Suren Baghdasaryan <surenb@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

lib/alloc_tag.c

@@ -129,7 +129,7 @@ size_t alloc_tag_top_users(struct codetag_bytes *tags, size_t count, bool can_sl
 
 static void __init procfs_init(void)
 {
-	proc_create_seq("allocinfo", 0444, NULL, &allocinfo_seq_op);
+	proc_create_seq("allocinfo", 0400, NULL, &allocinfo_seq_op);
 }
 
 static bool alloc_tag_module_unload(struct codetag_type *cttype,