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McKenney" , Peter Zijlstra , Thomas Gleixner , kernel-team@android.com, kernel-hardening@lists.openwall.com Subject: [RFC PATCH 13/21] list: Add integrity checking to hlist_nulls implementation Date: Tue, 24 Mar 2020 15:36:35 +0000 Message-Id: <20200324153643.15527-14-will@kernel.org> X-Mailer: git-send-email 2.20.1 In-Reply-To: <20200324153643.15527-1-will@kernel.org> References: <20200324153643.15527-1-will@kernel.org> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Extend the 'hlist_nulls' implementation so that it can optionally perform integrity checking in a similar fashion to the standard 'list' code when CONFIG_CHECK_INTEGRITY_LIST=y. On architectures without a trap value for ILLEGAL_POINTER_VALUE (i.e. all 32-bit architectures), explicit pointer/poison checks can help to mitigate UAF vulnerabilities such as the one exploited by "pingpongroot" (CVE-2015-3636). Cc: Kees Cook Cc: Paul E. McKenney Cc: Peter Zijlstra Signed-off-by: Will Deacon --- include/linux/list_nulls.h | 23 +++++++++++++++++++ lib/list_debug.c | 47 ++++++++++++++++++++++++++++++++++++++ 2 files changed, 70 insertions(+) diff --git a/include/linux/list_nulls.h b/include/linux/list_nulls.h index 48f33ae16381..379e097e92b0 100644 --- a/include/linux/list_nulls.h +++ b/include/linux/list_nulls.h @@ -35,6 +35,23 @@ struct hlist_nulls_node { ({ typeof(ptr) ____ptr = (ptr); \ !is_a_nulls(____ptr) ? hlist_nulls_entry(____ptr, type, member) : NULL; \ }) + +#ifdef CONFIG_CHECK_INTEGRITY_LIST +extern bool __hlist_nulls_add_head_valid(struct hlist_nulls_node *new, + struct hlist_nulls_head *head); +extern bool __hlist_nulls_del_valid(struct hlist_nulls_node *node); +#else +static inline bool __hlist_nulls_add_head_valid(struct hlist_nulls_node *new, + struct hlist_nulls_head *head) +{ + return true; +} +static inline bool __hlist_nulls_del_valid(struct hlist_nulls_node *node) +{ + return true; +} +#endif + /** * ptr_is_a_nulls - Test if a ptr is a nulls * @ptr: ptr to be tested @@ -79,6 +96,9 @@ static inline void hlist_nulls_add_head(struct hlist_nulls_node *n, { struct hlist_nulls_node *first = h->first; + if (!__hlist_nulls_add_head_valid(n, h)) + return; + n->next = first; n->pprev = &h->first; h->first = n; @@ -91,6 +111,9 @@ static inline void __hlist_nulls_del(struct hlist_nulls_node *n) struct hlist_nulls_node *next = n->next; struct hlist_nulls_node **pprev = n->pprev; + if (!__hlist_nulls_del_valid(n)) + return; + WRITE_ONCE(*pprev, next); if (!is_a_nulls(next)) WRITE_ONCE(next->pprev, pprev); diff --git a/lib/list_debug.c b/lib/list_debug.c index 03234ebd18c9..b3560de4accc 100644 --- a/lib/list_debug.c +++ b/lib/list_debug.c @@ -10,6 +10,7 @@ #include #include #include +#include /* * Check that the data structures for the list manipulations are reasonably @@ -139,3 +140,49 @@ bool __hlist_del_valid(struct hlist_node *node) return true; } EXPORT_SYMBOL(__hlist_del_valid); + +bool __hlist_nulls_add_head_valid(struct hlist_nulls_node *new, + struct hlist_nulls_head *head) +{ + struct hlist_nulls_node *first = head->first; + + if (CHECK_DATA_CORRUPTION(!is_a_nulls(first) && + first->pprev != &head->first, + "hlist_nulls_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_nulls_add_head double add: new (%px) == first (%px)", + new, first)) + return false; + + return true; +} +EXPORT_SYMBOL(__hlist_nulls_add_head_valid); + +bool __hlist_nulls_del_valid(struct hlist_nulls_node *node) +{ + struct hlist_nulls_node *prev, *next = node->next; + + if (CHECK_DATA_CORRUPTION(next == LIST_POISON1, + "hlist_nulls_del corruption: %px->next is LIST_POISON1 (%px)\n", + node, LIST_POISON1) || + CHECK_DATA_CORRUPTION(node->pprev == LIST_POISON2, + "hlist_nulls_del corruption: %px->pprev is LIST_POISON2 (%px)\n", + node, LIST_POISON2)) + return false; + + BUILD_BUG_ON(offsetof(struct hlist_nulls_node, next) != + offsetof(struct hlist_nulls_head, first)); + prev = container_of(node->pprev, struct hlist_nulls_node, next); + if (CHECK_DATA_CORRUPTION(prev->next != node, + "hlist_nulls_del corruption: prev->next should be %px, but was %px\n", + node, prev->next) || + CHECK_DATA_CORRUPTION(!is_a_nulls(next) && + next->pprev != &node->next, + "hlist_nulls_del corruption: next->pprev should be %px, but was %px\n", + &node->next, next->pprev)) + return false; + + return true; +} +EXPORT_SYMBOL(__hlist_nulls_del_valid); -- 2.20.1