From 0cc011c576aaa4de505046f7a6c90933d7c749a9 Mon Sep 17 00:00:00 2001
From: Guenter Roeck <linux@roeck-us.net>
Date: Tue, 31 May 2022 15:29:51 -0700
Subject: [PATCH] lib/list_debug.c: Detect uninitialized lists
Git-commit: 0cc011c576aaa4de505046f7a6c90933d7c749a9
Patch-mainline: v6.0-rc1
References: git-fixes

In some circumstances, attempts are made to add entries to or to remove
entries from an uninitialized list.  A prime example is
Amdgpu_bo_vm_destroy(): It is indirectly called from
ttm_bo_init_reserved() if that function fails, and tries to remove an
entry from a list.  However, that list is only initialized in
amdgpu_bo_create_vm() after the call to ttm_bo_init_reserved() returned
success.  This results in crashes such as

 BUG: kernel NULL pointer dereference, address: 0000000000000000
 #PF: supervisor read access in kernel mode
 #PF: error_code(0x0000) - not-present page
 PGD 0 P4D 0
 Oops: 0000 [#1] PREEMPT SMP NOPTI
 CPU: 1 PID: 1479 Comm: chrome Not tainted 5.10.110-15768-g29a72e65dae5
 Hardware name: Google Grunt/Grunt, BIOS Google_Grunt.11031.149.0 07/15/2020
 RIP: 0010:__list_del_entry_valid+0x26/0x7d
 ...
 Call Trace:
  amdgpu_bo_vm_destroy+0x48/0x8b
  ttm_bo_init_reserved+0x1d7/0x1e0
  amdgpu_bo_create+0x212/0x476
  ? amdgpu_bo_user_destroy+0x23/0x23
  ? kmem_cache_alloc+0x60/0x271
  amdgpu_bo_create_vm+0x40/0x7d
  amdgpu_vm_pt_create+0xe8/0x24b
 ...

Check if the list's prev and next pointers are NULL to catch such problems.

Link: https://lkml.kernel.org/r/20220531222951.92073-1-linux@roeck-us.net
Signed-off-by: Guenter Roeck <linux@roeck-us.net>
Cc: Steven Rostedt <rostedt@goodmis.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Acked-by: Takashi Iwai <tiwai@suse.de>

---
 lib/list_debug.c | 12 ++++++++++--
 1 file changed, 10 insertions(+), 2 deletions(-)

diff --git a/lib/list_debug.c b/lib/list_debug.c
index 9daa3fb9d1cd..d98d43f80958 100644
--- a/lib/list_debug.c
+++ b/lib/list_debug.c
@@ -20,7 +20,11 @@
 bool __list_add_valid(struct list_head *new, struct list_head *prev,
 		      struct list_head *next)
 {
-	if (CHECK_DATA_CORRUPTION(next->prev != prev,
+	if (CHECK_DATA_CORRUPTION(prev == NULL,
+			"list_add corruption. prev is NULL.\n") ||
+	    CHECK_DATA_CORRUPTION(next == NULL,
+			"list_add corruption. next is NULL.\n") ||
+	    CHECK_DATA_CORRUPTION(next->prev != prev,
 			"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,
@@ -42,7 +46,11 @@ bool __list_del_entry_valid(struct list_head *entry)
 	prev = entry->prev;
 	next = entry->next;
 
-	if (CHECK_DATA_CORRUPTION(next == LIST_POISON1,
+	if (CHECK_DATA_CORRUPTION(next == NULL,
+			"list_del corruption, %px->next is NULL\n", entry) ||
+	    CHECK_DATA_CORRUPTION(prev == NULL,
+			"list_del corruption, %px->prev is NULL\n", entry) ||
+	    CHECK_DATA_CORRUPTION(next == LIST_POISON1,
 			"list_del corruption, %px->next is LIST_POISON1 (%px)\n",
 			entry, LIST_POISON1) ||
 	    CHECK_DATA_CORRUPTION(prev == LIST_POISON2,
-- 
2.35.3