[PATCH 6.6 144/396] s390/zcrypt: fix reference counting on zcrypt card objects

Greg Kroah-Hartman
2024-04-01T16:42:40Z

From: Harald Freudenberger <freude@linux.ibm.com>

[ Upstream commit 50ed48c80fecbe17218afed4f8bed005c802976c ]

Tests with hot-plugging crytpo cards on KVM guests with debug
kernel build revealed an use after free for the load field of
the struct zcrypt_card. The reason was an incorrect reference
handling of the zcrypt card object which could lead to a free
of the zcrypt card object while it was still in use.

This is an example of the slab message:

kernel: 0x00000000885a7512-0x00000000885a7513 @offset=1298. First byte 0x68 instead of 0x6b
kernel: Allocated in zcrypt_card_alloc+0x36/0x70 [zcrypt] age=18046 cpu=3 pid=43
kernel: kmalloc_trace+0x3f2/0x470
kernel: zcrypt_card_alloc+0x36/0x70 [zcrypt]
kernel: zcrypt_cex4_card_probe+0x26/0x380 [zcrypt_cex4]
kernel: ap_device_probe+0x15c/0x290
kernel: really_probe+0xd2/0x468
kernel: driver_probe_device+0x40/0xf0
kernel: __device_attach_driver+0xc0/0x140
kernel: bus_for_each_drv+0x8c/0xd0
kernel: __device_attach+0x114/0x198
kernel: bus_probe_device+0xb4/0xc8
kernel: device_add+0x4d2/0x6e0
kernel: ap_scan_adapter+0x3d0/0x7c0
kernel: ap_scan_bus+0x5a/0x3b0
kernel: ap_scan_bus_wq_callback+0x40/0x60
kernel: process_one_work+0x26e/0x620
kernel: worker_thread+0x21c/0x440
kernel: Freed in zcrypt_card_put+0x54/0x80 [zcrypt] age=9024 cpu=3 pid=43
kernel: kfree+0x37e/0x418
kernel: zcrypt_card_put+0x54/0x80 [zcrypt]
kernel: ap_device_remove+0x4c/0xe0
kernel: device_release_driver_internal+0x1c4/0x270
kernel: bus_remove_device+0x100/0x188
kernel: device_del+0x164/0x3c0
kernel: device_unregister+0x30/0x90
kernel: ap_scan_adapter+0xc8/0x7c0
kernel: ap_scan_bus+0x5a/0x3b0
kernel: ap_scan_bus_wq_callback+0x40/0x60
kernel: process_one_work+0x26e/0x620
kernel: worker_thread+0x21c/0x440
kernel: kthread+0x150/0x168
kernel: __ret_from_fork+0x3c/0x58
kernel: ret_from_fork+0xa/0x30
kernel: Slab 0x00000372022169c0 objects=20 used=18 fp=0x00000000885a7c88 flags=0x3ffff00000000a00(workingset|slab|node=0|zone=1|lastcpupid=0x1ffff)
kernel: Object 0x00000000885a74b8 @offset=1208 fp=0x00000000885a7c88
kernel: Redzone 00000000885a74b0: bb bb bb bb bb bb bb bb ........
kernel: Object 00000000885a74b8: 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b kkkkkkkkkkkkkkkk
kernel: Object 00000000885a74c8: 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b kkkkkkkkkkkkkkkk
kernel: Object 00000000885a74d8: 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b kkkkkkkkkkkkkkkk
kernel: Object 00000000885a74e8: 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b kkkkkkkkkkkkkkkk
kernel: Object 00000000885a74f8: 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b kkkkkkkkkkkkkkkk
kernel: Object 00000000885a7508: 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 68 4b 6b 6b 6b a5 kkkkkkkkkkhKkkk.
kernel: Redzone 00000000885a7518: bb bb bb bb bb bb bb bb ........
kernel: Padding 00000000885a756c: 5a 5a 5a 5a 5a 5a 5a 5a 5a 5a 5a 5a ZZZZZZZZZZZZ
kernel: CPU: 0 PID: 387 Comm: systemd-udevd Not tainted 6.8.0-HF #2
kernel: Hardware name: IBM 3931 A01 704 (KVM/Linux)
kernel: Call Trace:
kernel: [<00000000ca5ab5b8>] dump_stack_lvl+0x90/0x120
kernel: [<00000000c99d78bc>] check_bytes_and_report+0x114/0x140
kernel: [<00000000c99d53cc>] check_object+0x334/0x3f8
kernel: [<00000000c99d820c>] alloc_debug_processing+0xc4/0x1f8
kernel: [<00000000c99d852e>] get_partial_node.part.0+0x1ee/0x3e0
kernel: [<00000000c99d94ec>] ___slab_alloc+0xaf4/0x13c8
kernel: [<00000000c99d9e38>] __slab_alloc.constprop.0+0x78/0xb8
kernel: [<00000000c99dc8dc>] __kmalloc+0x434/0x590
kernel: [<00000000c9b4c0ce>] ext4_htree_store_dirent+0x4e/0x1c0
kernel: [<00000000c9b908a2>] htree_dirblock_to_tree+0x17a/0x3f0
kernel: [<00000000c9b919dc>] ext4_htree_fill_tree+0x134/0x400
kernel: [<00000000c9b4b3d0>] ext4_dx_readdir+0x160/0x2f0
kernel: [<00000000c9b4bedc>] ext4_readdir+0x5f4/0x760
kernel: [<00000000c9a7efc4>] iterate_dir+0xb4/0x280
kernel: [<00000000c9a7f1ea>] __do_sys_getdents64+0x5a/0x120
kernel: [<00000000ca5d6946>] __do_syscall+0x256/0x310
kernel: [<00000000ca5eea10>] system_call+0x70/0x98
kernel: INFO: lockdep is turned off.
kernel: FIX kmalloc-96: Restoring Poison 0x00000000885a7512-0x00000000885a7513=0x6b
kernel: FIX kmalloc-96: Marking all objects used

The fix is simple: Before use of the queue not only the queue object
but also the card object needs to increase it's reference count
with a call to zcrypt_card_get(). Similar after use of the queue
not only the queue but also the card object's reference count is
decreased with zcrypt_card_put().

Signed-off-by: Harald Freudenberger <freude@linux.ibm.com>
Reviewed-by: Holger Dengler <dengler@linux.ibm.com>
Cc: stable@vger.kernel.org
Signed-off-by: Heiko Carstens <hca@linux.ibm.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
drivers/s390/crypto/zcrypt_api.c | 2 ++
1 file changed, 2 insertions(+)

diff --git a/drivers/s390/crypto/zcrypt_api.c b/drivers/s390/crypto/zcrypt_api.c
index ce04caa7913fb..357889cc03f0a 100644
--- a/drivers/s390/crypto/zcrypt_api.c
+++ b/drivers/s390/crypto/zcrypt_api.c
@@ -579,6 +579,7 @@ static inline struct zcrypt_queue *zcrypt_pick_queue(struct zcrypt_card *zc,
{
if (!zq || !try_module_get(zq->queue->ap_dev.device.driver->owner))
return NULL;
+ zcrypt_card_get(zc);
zcrypt_queue_get(zq);
get_device(&zq->queue->ap_dev.device);
atomic_add(weight, &zc->load);
@@ -598,6 +599,7 @@ static inline void zcrypt_drop_queue(struct zcrypt_card *zc,
atomic_sub(weight, &zq->load);
put_device(&zq->queue->ap_dev.device);
zcrypt_queue_put(zq);
+ zcrypt_card_put(zc);
module_put(mod);
}

--
2.43.0