kernel/resource: fix kfree() of bootmem memory again

Since commit ebff7d8f270d ("mem hotunplug: fix kfree() of bootmem
memory"), we could get a resource allocated during boot via
alloc_resource().  And it's required to release the resource using
free_resource().  Howerver, many people use kfree directly which will
result in kernel BUG.  In order to fix this without fixing every call
site, just leak a couple of bytes in such corner case.

Link: https://lkml.kernel.org/r/20220217083619.19305-1-linmiaohe@huawei.com
Fixes: ebff7d8f270d ("mem hotunplug: fix kfree() of bootmem memory")
Signed-off-by: Miaohe Lin <linmiaohe@huawei.com>
Suggested-by: David Hildenbrand <david@redhat.com>
Cc: Dan Williams <dan.j.williams@intel.com>
Cc: Alistair Popple <apopple@nvidia.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/kernel/resource.c b/kernel/resource.c
index 9c08d6e..34eaee1 100644 (file)
--- a/kernel/resource.c
+++ b/kernel/resource.c
@@ -56,14 +56,6 @@ struct resource_constraint {
 
 static DEFINE_RWLOCK(resource_lock);
 
-/*
- * For memory hotplug, there is no way to free resource entries allocated
- * by boot mem after the system is up. So for reusing the resource entry
- * we need to remember the resource.
- */
-static struct resource *bootmem_resource_free;
-static DEFINE_SPINLOCK(bootmem_resource_lock);
-
 static struct resource *next_resource(struct resource *p)
 {
        if (p->child)
@@ -160,36 +152,19 @@ __initcall(ioresources_init);
 
 static void free_resource(struct resource *res)
 {
-       if (!res)
-               return;
-
-       if (!PageSlab(virt_to_head_page(res))) {
-               spin_lock(&bootmem_resource_lock);
-               res->sibling = bootmem_resource_free;
-               bootmem_resource_free = res;
-               spin_unlock(&bootmem_resource_lock);
-       } else {
+       /**
+        * If the resource was allocated using memblock early during boot
+        * we'll leak it here: we can only return full pages back to the
+        * buddy and trying to be smart and reusing them eventually in
+        * alloc_resource() overcomplicates resource handling.
+        */
+       if (res && PageSlab(virt_to_head_page(res)))
                kfree(res);
-       }
 }
 
 static struct resource *alloc_resource(gfp_t flags)
 {
-       struct resource *res = NULL;
-
-       spin_lock(&bootmem_resource_lock);
-       if (bootmem_resource_free) {
-               res = bootmem_resource_free;
-               bootmem_resource_free = res->sibling;
-       }
-       spin_unlock(&bootmem_resource_lock);
-
-       if (res)
-               memset(res, 0, sizeof(struct resource));
-       else
-               res = kzalloc(sizeof(struct resource), flags);
-
-       return res;
+       return kzalloc(sizeof(struct resource), flags);
 }
 
 /* Return the conflict entry if you can't request it */