linux-kernel - [PATCH] lib/test_vmalloc.c: demote vmalloc_test_init to late

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Message-Id: <20250620142448.653645-1-00107082@163.com>
Date: Fri, 20 Jun 2025 22:24:48 +0800
From: David Wang <00107082@....com>
To: akpm@...ux-foundation.org,
	urezki@...il.com
Cc: linux-mm@...ck.org,
	linux-kernel@...r.kernel.org,
	harry.yoo@...cle.com,
	kent.overstreet@...ux.dev,
	surenb@...gle.com,
	David Wang <00107082@....com>,
	kernel test robot <oliver.sang@...el.com>
Subject: [PATCH] lib/test_vmalloc.c: demote vmalloc_test_init to late_initcall

Commit 2d76e79315e4 ("lib/test_vmalloc.c: allow built-in execution")
enable test_vmalloc module to be built into kernel directly, but
vmalloc_test_init depends on alloc_tag module via alloc_tag_top_users().

When a kernel build with following config:

CONFIG_TEST_VMALLOC=y
CONFIG_MEM_ALLOC_PROFILING=y
CONFIG_MEM_ALLOC_PROFILING_ENABLED_BY_DEFAULT=y
CONFIG_MEM_ALLOC_PROFILING_DEBUG=y

If vmalloc_test_init() run before alloc_tag_init(), memory
failure tests would invoke alloc_tag_top_users() which is not
ready to use and cause kernel BUG:

 [  135.116045] BUG: kernel NULL pointer dereference, address: 0000000000000030
 [  135.116063] #PF: supervisor read access in kernel mode
 [  135.116074] #PF: error_code(0x0000) - not-present page
 [  135.116085] PGD 0 P4D 0
 [  135.116094] Oops: Oops: 0000 [#1] SMP NOPTI
 [  135.116123] Tainted: [E]=UNSIGNED_MODULE
 [  135.116132] Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.2-debian-1.16.2-1 04/01/2014
 [  135.116148] RIP: 0010:down_read_trylock+0x1d/0x80
 [  135.116188] RSP: 0000:ffffb5e481a9b8f8 EFLAGS: 00010246
 [  135.116200] RAX: ffff93dc8a5ac700 RBX: 0000000000000030 RCX: 8000000000000007
 [  135.116214] RDX: 0000000000000001 RSI: 000000000000000a RDI: ffffffff93d2e733
 [  135.116228] RBP: ffffb5e481a9b9a0 R08: 0000000000000000 R09: 0000000000000003
 [  135.116241] R10: ffffb5e481a9b860 R11: ffffffff94ec6328 R12: ffffb5e481a9b9b0
 [  135.116255] R13: 0000000000000003 R14: 0000000000000001 R15: ffffffff94e0c580
 [  135.116271] FS:  00007fd41947e540(0000) GS:ffff93dd6654a000(0000) knlGS:0000000000000000
 [  135.116286] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
 [  135.116298] CR2: 0000000000000030 CR3: 00000001099f8000 CR4: 0000000000350ef0
 [  135.116314] Call Trace:
 [  135.116321]  <TASK>
 [  135.116328]  codetag_trylock_module_list+0x9/0x20
 [  135.116342]  alloc_tag_top_users+0x153/0x1b0
 [  135.116354]  ? srso_return_thunk+0x5/0x5f
 [  135.116365]  ? _printk+0x57/0x80
 [  135.116378]  __show_mem+0xeb/0x210
 [  135.116394]  ? dump_header+0x2ce/0x3e0
 [  135.116405]  dump_header+0x2ce/0x3e0

Demote vmalloc_test_init to late_initcall can make sure alloc_tag
module got initialized before test_vmalloc module.

Link: https://lore.kernel.org/lkml/20250620100258.595495-1-00107082@163.com/
Reported-by: kernel test robot <oliver.sang@...el.com>
Closes: https://lore.kernel.org/oe-lkp/202506181351.bba867dd-lkp@intel.com
Fixes: 2d76e79315e4 ("lib/test_vmalloc.c: allow built-in execution")
Signed-off-by: David Wang <00107082@....com>
---
 lib/test_vmalloc.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/lib/test_vmalloc.c b/lib/test_vmalloc.c
index 1b0b59549aaf..5af009df56ad 100644
--- a/lib/test_vmalloc.c
+++ b/lib/test_vmalloc.c
@@ -598,7 +598,7 @@ static int __init vmalloc_test_init(void)
 	return IS_BUILTIN(CONFIG_TEST_VMALLOC) ? 0:-EAGAIN;
 }
 
-module_init(vmalloc_test_init)
+late_initcall(vmalloc_test_init)
 
 MODULE_LICENSE("GPL");
 MODULE_AUTHOR("Uladzislau Rezki");
-- 
2.39.2