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Subject[RFC PATCH 19/21] list_bl: Extend integrity checking to cover the same cases as 'hlist'
Date
The list integrity checks for 'hlist_bl' are missing a number of cases
that are covered by other list implementations (e.g. 'hlist'), such as
validating 'next' and 'pprev' pointers when adding and deleting nodes.

Extend the list_bl integrity checks to bring them up to the same level
as for other list implementations.

Cc: Kees Cook <keescook@chromium.org>
Cc: Paul E. McKenney <paulmck@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Signed-off-by: Will Deacon <will@kernel.org>
---
lib/list_debug.c | 48 ++++++++++++++++++++++++++++++++++++++++--------
1 file changed, 40 insertions(+), 8 deletions(-)

diff --git a/lib/list_debug.c b/lib/list_debug.c
index 9591fa6c9337..3be50b5c8014 100644
--- a/lib/list_debug.c
+++ b/lib/list_debug.c
@@ -7,6 +7,7 @@

#include <linux/export.h>
#include <linux/list.h>
+#include <linux/list_bl.h>
#include <linux/bug.h>
#include <linux/kernel.h>
#include <linux/rculist.h>
@@ -190,27 +191,58 @@ EXPORT_SYMBOL(__hlist_nulls_del_valid);
bool __hlist_bl_add_head_valid(struct hlist_bl_node *new,
struct hlist_bl_head *head)
{
+ struct hlist_bl_node *first = hlist_bl_first(head);
unsigned long hlock = (unsigned long)head->first & LIST_BL_LOCKMASK;
unsigned long nlock = (unsigned long)new & LIST_BL_LOCKMASK;

- return !(CHECK_DATA_CORRUPTION(nlock,
+ if (CHECK_DATA_CORRUPTION(nlock,
"hlist_bl_add_head: node is locked\n") ||
- CHECK_DATA_CORRUPTION(hlock != LIST_BL_LOCKMASK,
- "hlist_bl_add_head: head is unlocked\n"));
+ CHECK_DATA_CORRUPTION(hlock != LIST_BL_LOCKMASK,
+ "hlist_bl_add_head: head is unlocked\n"))
+ return false;
+
+ if (CHECK_DATA_CORRUPTION(first && first->pprev != &head->first,
+ "hlist_bl_add_head corruption: first->pprev should be &head->first (%px), but was %px (first=%px)",
+ &head->first, first->pprev, first) ||
+ CHECK_DATA_CORRUPTION(new == first,
+ "hlist_bl_add_head double add: new (%px) == first (%px)",
+ new, first))
+ return false;
+
+ return true;
}
EXPORT_SYMBOL(__hlist_bl_add_head_valid);

bool __hlist_bl_del_valid(struct hlist_bl_node *node)
{
+ struct hlist_bl_node *prev, *next = node->next;
unsigned long nlock = (unsigned long)node & LIST_BL_LOCKMASK;
+ unsigned long pnext;

- return !(CHECK_DATA_CORRUPTION(nlock,
- "hlist_bl_del_valid: node locked") ||
- CHECK_DATA_CORRUPTION(node->next == LIST_POISON1,
+ if (CHECK_DATA_CORRUPTION(nlock,
+ "hlist_bl_del corruption: node is locked") ||
+ CHECK_DATA_CORRUPTION(next == LIST_POISON1,
"hlist_bl_del corruption, %px->next is LIST_POISON1 (%px)\n",
node, LIST_POISON1) ||
- CHECK_DATA_CORRUPTION(node->pprev == LIST_POISON2,
+ CHECK_DATA_CORRUPTION(node->pprev == LIST_POISON2,
"hlist_bl_del corruption, %px->pprev is LIST_POISON2 (%px)\n",
- node, LIST_POISON2));
+ node, LIST_POISON2))
+ return false;
+
+ BUILD_BUG_ON(offsetof(struct hlist_bl_node, next) !=
+ offsetof(struct hlist_bl_head, first));
+ prev = container_of(node->pprev, struct hlist_bl_node, next);
+ pnext = (unsigned long)prev->next & ~LIST_BL_LOCKMASK;
+ if (CHECK_DATA_CORRUPTION((unsigned long)next & LIST_BL_LOCKMASK,
+ "hlist_bl_del_corruption: node->next is locked") ||
+ CHECK_DATA_CORRUPTION((struct hlist_bl_node *)pnext != node,
+ "hlist_bl_del corruption: prev->next should be %px, but was %lx\n",
+ node, pnext) ||
+ CHECK_DATA_CORRUPTION(next && next->pprev != &node->next,
+ "hlist_bl_del corruption: next->pprev should be %px, but was %px\n",
+ &node->next, next->pprev))
+ return false;
+
+ return true;
}
EXPORT_SYMBOL(__hlist_bl_del_valid);
--
2.20.1
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