alloc_tag: add sequence number for module and iterator

Codetag iterator use <id,address> pair to guarantee the validness.  But
both id and address can be reused, there is theoretical possibility when
module inserted right after another module removed, kmalloc returns an
address same as the address kfree by previous module and IDR key reuses
the key recently removed.

Add a sequence number to codetag_module and code_iterator, the sequence
number is strickly incremented whenever a module is loaded.  An iterator
is valid if and only if its sequence number match codetag_module's.

Link: https://lkml.kernel.org/r/20250609064200.112639-1-00107082@163.com
Signed-off-by: David Wang <00107082@163.com>
Acked-by: Suren Baghdasaryan <surenb@google.com>
Cc: Kent Overstreet <kent.overstreet@linux.dev>
Cc: Tim Chen <tim.c.chen@linux.intel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

diff --git a/include/linux/codetag.h b/include/linux/codetag.h
index 5f2b9a1f722c763d37192f12bd4f5d831d999f14..457ed8fd321443cb3a4bfc15abe8e4e67e9ae362 100644 (file)
--- a/include/linux/codetag.h
+++ b/include/linux/codetag.h
@@ -54,6 +54,7 @@ struct codetag_iterator {
        struct codetag_module *cmod;
        unsigned long mod_id;
        struct codetag *ct;
+       unsigned long mod_seq;
 };
 
 #ifdef MODULE

diff --git a/lib/codetag.c b/lib/codetag.c
index 650d54d7e14da687cbeea54b0a610d5616f8f35e..545911cebd25a6489e87c64515cd0d6429475753 100644 (file)
--- a/lib/codetag.c
+++ b/lib/codetag.c
@@ -11,8 +11,14 @@ struct codetag_type {
        struct list_head link;
        unsigned int count;
        struct idr mod_idr;
-       struct rw_semaphore mod_lock; /* protects mod_idr */
+       /*
+        * protects mod_idr, next_mod_seq,
+        * iter->mod_seq and cmod->mod_seq
+        */
+       struct rw_semaphore mod_lock;
        struct codetag_type_desc desc;
+       /* generates unique sequence number for module load */
+       unsigned long next_mod_seq;
 };
 
 struct codetag_range {
@@ -23,6 +29,7 @@ struct codetag_range {
 struct codetag_module {
        struct module *mod;
        struct codetag_range range;
+       unsigned long mod_seq;
 };
 
 static DEFINE_MUTEX(codetag_lock);
@@ -48,6 +55,7 @@ struct codetag_iterator codetag_get_ct_iter(struct codetag_type *cttype)
                .cmod = NULL,
                .mod_id = 0,
                .ct = NULL,
+               .mod_seq = 0,
        };
 
        return iter;
@@ -91,11 +99,13 @@ struct codetag *codetag_next_ct(struct codetag_iterator *iter)
                if (!cmod)
                        break;
 
-               if (cmod != iter->cmod) {
+               if (!iter->cmod || iter->mod_seq != cmod->mod_seq) {
                        iter->cmod = cmod;
+                       iter->mod_seq = cmod->mod_seq;
                        ct = get_first_module_ct(cmod);
-               } else
+               } else {
                        ct = get_next_module_ct(iter);
+               }
 
                if (ct)
                        break;
@@ -191,6 +201,7 @@ static int codetag_module_init(struct codetag_type *cttype, struct module *mod)
        cmod->range = range;
 
        down_write(&cttype->mod_lock);
+       cmod->mod_seq = ++cttype->next_mod_seq;
        mod_id = idr_alloc(&cttype->mod_idr, cmod, 0, 0, GFP_KERNEL);
        if (mod_id >= 0) {
                if (cttype->desc.module_load) {