Merge tag 'printk-hash-pointer-4.15-rc2' of git://github.com/tcharding/linux

Pull printk pointer hashing update from Tobin Harding:
 "Here is the patch set that implements hashing of printk specifier %p.

  First we have two clean up patches then we do the hashing. Hashing is
  done via the SipHash algorithm. The next patch adds printk specifier
  %px for printing pointers when we _really_ want to see the address i.e
  %px is functionally equivalent to %lx. Final patch in the set fixes
  KASAN since we break it by hashing %p.

  For the record here is the justification for the series:

    Currently there exist approximately 14 000 places in the Kernel
    where addresses are being printed using an unadorned %p. This
    potentially leaks sensitive information about the Kernel layout in
    memory. Many of these calls are stale, instead of fixing every call
    we hash the address by default before printing. We then add %px to
    provide a way to print the actual address. Although this is
    achievable using %lx, using %px will assist us if we ever want to
    change pointer printing behaviour. %px is more uniquely grep'able
    (there are already >50 000 uses of %lx).

    The added advantage of hashing %p is that security is now opt-out,
    if you _really_ want the address you have to work a little harder
    and use %px.

  This will of course break some users, forcing code printing needed
  addresses to be updated"

[ I do expect this to be an annoyance, and a number of %px users to be
  added for debuggability. But nobody is willing to audit existing %p
  users for information leaks, and a number of places really only use
  the pointer as an object identifier rather than really 'I need the
  address'.

  IOW - sorry for the inconvenience, but it's the least inconvenient of
  the options.    - Linus ]

* tag 'printk-hash-pointer-4.15-rc2' of git://github.com/tcharding/linux:
  kasan: use %px to print addresses instead of %p
  vsprintf: add printk specifier %px
  printk: hash addresses printed with %p
  vsprintf: refactor %pK code out of pointer()
  docs: correct documentation for %pK

1 files changed, 4 insertions, 4 deletions

diff --git a/mm/kasan/report.c b/mm/kasan/report.c
index 6bcfb01ba038..410c8235e671 100644
--- a/mm/kasan/report.c
+++ b/mm/kasan/report.c
@@ -134,7 +134,7 @@ static void print_error_description(struct kasan_access_info *info)
 
 	pr_err("BUG: KASAN: %s in %pS\n",
 		bug_type, (void *)info->ip);
-	pr_err("%s of size %zu at addr %p by task %s/%d\n",
+	pr_err("%s of size %zu at addr %px by task %s/%d\n",
 		info->is_write ? "Write" : "Read", info->access_size,
 		info->access_addr, current->comm, task_pid_nr(current));
 }
@@ -206,7 +206,7 @@ static void describe_object_addr(struct kmem_cache *cache, void *object,
 	const char *rel_type;
 	int rel_bytes;
 
-	pr_err("The buggy address belongs to the object at %p\n"
+	pr_err("The buggy address belongs to the object at %px\n"
 	       " which belongs to the cache %s of size %d\n",
 		object, cache->name, cache->object_size);
 
@@ -225,7 +225,7 @@ static void describe_object_addr(struct kmem_cache *cache, void *object,
 	}
 
 	pr_err("The buggy address is located %d bytes %s of\n"
-	       " %d-byte region [%p, %p)\n",
+	       " %d-byte region [%px, %px)\n",
 		rel_bytes, rel_type, cache->object_size, (void *)object_addr,
 		(void *)(object_addr + cache->object_size));
 }
@@ -302,7 +302,7 @@ static void print_shadow_for_address(const void *addr)
 		char shadow_buf[SHADOW_BYTES_PER_ROW];
 
 		snprintf(buffer, sizeof(buffer),
-			(i == 0) ? ">%p: " : " %p: ", kaddr);
+			(i == 0) ? ">%px: " : " %px: ", kaddr);
 		/*
 		 * We should not pass a shadow pointer to generic
 		 * function, because generic functions may try to