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From: Matthew Wilcox <willy@infradead.org>
To: "Tobin C. Harding" <me@tobin.cc>
Cc: linux-kernel@vger.kernel.org, Eric Biggers <ebiggers3@gmail.com>
Subject: [PATCH] list_debug: Print unmangled addresses
Date: Sun, 1 Apr 2018 15:32:37 -0700
Message-ID: <20180401223237.GV13332@bombadil.infradead.org> (raw)

From: Matthew Wilcox <mawilcox@microsoft.com>

The entire point of printing the pointers in list_debug is to see if
there's any useful information in them (eg poison values, ASCII, etc);
obscuring them to see if they compare equal makes them much less useful.
If an attacker can force this message to be printed, we've already lost.

Signed-off-by: Matthew Wilcox <mawilcox@microsoft.com>

diff --git a/lib/list_debug.c b/lib/list_debug.c
index a34db8d27667..5d5424b51b74 100644
--- a/lib/list_debug.c
+++ b/lib/list_debug.c
@@ -21,13 +21,13 @@ bool __list_add_valid(struct list_head *new, struct list_head *prev,
 		      struct list_head *next)
 {
 	if (CHECK_DATA_CORRUPTION(next->prev != prev,
-			"list_add corruption. next->prev should be prev (%p), but was %p. (next=%p).\n",
+			"list_add corruption. next->prev should be prev (%px), but was %px. (next=%px).\n",
 			prev, next->prev, next) ||
 	    CHECK_DATA_CORRUPTION(prev->next != next,
-			"list_add corruption. prev->next should be next (%p), but was %p. (prev=%p).\n",
+			"list_add corruption. prev->next should be next (%px), but was %px. (prev=%px).\n",
 			next, prev->next, prev) ||
 	    CHECK_DATA_CORRUPTION(new == prev || new == next,
-			"list_add double add: new=%p, prev=%p, next=%p.\n",
+			"list_add double add: new=%px, prev=%px, next=%px.\n",
 			new, prev, next))
 		return false;
 
@@ -43,16 +43,16 @@ bool __list_del_entry_valid(struct list_head *entry)
 	next = entry->next;
 
 	if (CHECK_DATA_CORRUPTION(next == LIST_POISON1,
-			"list_del corruption, %p->next is LIST_POISON1 (%p)\n",
+			"list_del corruption, %px->next is LIST_POISON1 (%px)\n",
 			entry, LIST_POISON1) ||
 	    CHECK_DATA_CORRUPTION(prev == LIST_POISON2,
-			"list_del corruption, %p->prev is LIST_POISON2 (%p)\n",
+			"list_del corruption, %px->prev is LIST_POISON2 (%px)\n",
 			entry, LIST_POISON2) ||
 	    CHECK_DATA_CORRUPTION(prev->next != entry,
-			"list_del corruption. prev->next should be %p, but was %p\n",
+			"list_del corruption. prev->next should be %px, but was %px\n",
 			entry, prev->next) ||
 	    CHECK_DATA_CORRUPTION(next->prev != entry,
-			"list_del corruption. next->prev should be %p, but was %p\n",
+			"list_del corruption. next->prev should be %px, but was %px\n",
 			entry, next->prev))
 		return false;
 

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Thread overview: 2+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-04-01 22:32 Matthew Wilcox [this message]
2018-04-03  3:31 ` Tobin C. Harding

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