[PATCH] fault-inject: fix boot failure with fault injection boot parameters

[PATCH] fault-inject: fix boot failure with fault injection boot parameters

[Sang-Heon Jeon]

Since commit e9bc360b105c ("fault-inject: use prandom where
cryptographically secure randomness is not needed"), setup_fault_attr()
calls prandom_init_once(), which calls kmalloc() and schedule_work().

But setup_fault_attr() can be called from __setup handlers before slab
and workqueues are initialized, so any fault injection boot parameter
leads to boot failure.

So use DO_ONCE_LITE() instead.

Fixes: e9bc360b105c ("fault-inject: use prandom where cryptographically secure randomness is not needed")
Cc: stable@vger.kernel.org
Signed-off-by: Sang-Heon Jeon <ekffu200098@gmail.com>
---
QEMU-based test results
- build with gcc 16.2 + x86_64, booted with "failslab=1,0,-1,0"

1) AS-IS (before fix) 
[    0.090415] BUG: kernel NULL pointer dereference, address: 0000000000000018
[    0.091661] #PF: supervisor read access in kernel mode
[    0.092639] #PF: error_code(0x0000) - not-present page
[    0.093593] PGD 0 P4D 0 
[    0.094051] Oops: Oops: 0000 [#1] SMP NOPTI
[    0.094800] CPU: 0 UID: 0 PID: 0 Comm: swapper Not tainted 7.3.0 #2 PREEMPT(undef) 
[    0.096178] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.17.0-debian-1.17.0-1ubuntu1 04/01/2014
[    0.098046] RIP: 0010:__kmalloc_cache_noprof+0x142/0x370
[    0.099024] Code: ea c1 ea 08 41 89 d5 41 83 e5 01 8b 53 1c 0f 1f 44 00 00 45 84 ed 74 12 4d 85 d2 74 0d 4c 89 d7 31 f6 e8 e1 2d e1 00 49 89 c2 <44> 8b 43 18 48 8b 74 24 50 0f 1fb
[    0.102388] RSP: 0000:ffffffff82c03d50 EFLAGS: 00010046
[    0.103326] RAX: 0000000000000000 RBX: 0000000000000000 RCX: 0000000000000000
[    0.104604] RDX: 0000000000000001 RSI: 0000000000000020 RDI: 0000000000000000
[    0.105883] RBP: 0000000000000820 R08: ffff88807dda6c70 R09: 46ad46184e3f2c64
[    0.107194] R10: 0000000000000000 R11: 46ad46184e3f2c64 R12: 0000000000000030
[    0.108472] R13: 0000000000000001 R14: 0000000000000008 R15: ffff88807ffd3ab1
[    0.109832] FS:  0000000000000000(0000) GS:ffff8880fa4ac000(0000) knlGS:0000000000000000
[    0.111284] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[    0.112311] CR2: 0000000000000018 CR3: 0000000002c30000 CR4: 00000000000000b0
[    0.113616] Call Trace:
[    0.114059]  <TASK>
[    0.114462]  ? once_disable_jump+0x20/0x80
[    0.115202]  once_disable_jump+0x20/0x80
[    0.115905]  setup_fault_attr+0xe6/0xf0
[    0.116597]  unknown_bootoption+0x111/0x210
[    0.117352]  parse_args+0x14f/0x3c0
[    0.117983]  ? __pfx_unknown_bootoption+0x10/0x10
[    0.118839]  start_kernel+0x3b8/0x7c0
[    0.119539]  ? __pfx_unknown_bootoption+0x10/0x10
[    0.120435]  x86_64_start_reservations+0x24/0x30
[    0.121310]  x86_64_start_kernel+0xd1/0xe0
[    0.122278]  common_startup_64+0x13e/0x158
[    0.124133]  </TASK>
[    0.124756] Modules linked in:
[    0.125309] CR2: 0000000000000018
[    0.125905] ---[ end trace 0000000000000000 ]---
[    0.126741] RIP: 0010:__kmalloc_cache_noprof+0x142/0x370
[    0.127704] Code: ea c1 ea 08 41 89 d5 41 83 e5 01 8b 53 1c 0f 1f 44 00 00 45 84 ed 74 12 4d 85 d2 74 0d 4c 89 d7 31 f6 e8 e1 2d e1 00 49 89 c2 <44> 8b 43 18 48 8b 74 24 50 0f 1fb
[    0.131129] RSP: 0000:ffffffff82c03d50 EFLAGS: 00010046
[    0.132126] RAX: 0000000000000000 RBX: 0000000000000000 RCX: 0000000000000000
[    0.133483] RDX: 0000000000000001 RSI: 0000000000000020 RDI: 0000000000000000
[    0.134843] RBP: 0000000000000820 R08: ffff88807dda6c70 R09: 46ad46184e3f2c64
[    0.136206] R10: 0000000000000000 R11: 46ad46184e3f2c64 R12: 0000000000000030
[    0.137565] R13: 0000000000000001 R14: 0000000000000008 R15: ffff88807ffd3ab1
[    0.138928] FS:  0000000000000000(0000) GS:ffff8880fa4ac000(0000) knlGS:0000000000000000
[    0.142705] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[    0.143741] CR2: 0000000000000018 CR3: 0000000002c30000 CR4: 00000000000000b0
[    0.145037] Kernel panic - not syncing: Attempted to kill the idle task!
[    0.146284] ---[ end Kernel panic - not syncing: Attempted to kill the idle task! ]---2) TO-BE (after fix)

2) TO-BE (after fix)
- boot succeeded

---
 lib/fault-inject.c | 8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)

diff --git a/lib/fault-inject.c b/lib/fault-inject.c
index 02916ef2761c..9182d457baf5 100644
--- a/lib/fault-inject.c
+++ b/lib/fault-inject.c
@@ -1,6 +1,7 @@
 // SPDX-License-Identifier: GPL-2.0-only
 #include <linux/kernel.h>
 #include <linux/init.h>
+#include <linux/once_lite.h>
 #include <linux/prandom.h>
 #include <linux/debugfs.h>
 #include <linux/sched.h>
@@ -50,7 +51,12 @@ int setup_fault_attr(struct fault_attr *attr, char *str)
 		return 0;
 	}
 
-	prandom_init_once(&fault_rnd_state);
+	/*
+	 * __setup handlers run before slab and workqueues are initialized,
+	 * but prandom_init_once() calls kmalloc() and schedule_work(). So use
+	 * DO_ONCE_LITE() instead.
+	 */
+	DO_ONCE_LITE(prandom_seed_full_state, &fault_rnd_state);
 
 	attr->probability = probability;
 	attr->interval = interval;

base-commit: c2366a2edc886a5a02d2a43de8b1c6ec09bab840
-- 
2.53.0