Subject: CVE-2024-26957: s390/zcrypt: fix reference counting on zcrypt card objects

From: Greg Kroah-Hartman <[email-masked]>

Description
===========

In the Linux kernel, the following vulnerability has been resolved:

s390/zcrypt: fix reference counting on zcrypt card objects

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().

The Linux kernel CVE team has assigned CVE-2024-26957 to this issue.

Affected and fixed versions
===========================

	Fixed in 4.19.312 with commit 7e500849fa55
	Fixed in 5.4.274 with commit 9daddee03de3
	Fixed in 5.10.215 with commit 6470078ab3d8
	Fixed in 5.15.154 with commit a55677878b93
	Fixed in 6.1.84 with commit b7f6c3630eb3
	Fixed in 6.6.24 with commit a64ab862e84e
	Fixed in 6.7.12 with commit befb7f889594
	Fixed in 6.8.3 with commit 394b6d8bbdf9
	Fixed in 6.9 with commit 50ed48c80fec

Please see https://www.kernel.org for a full list of currently supported
kernel versions by the kernel community.

Unaffected versions might change over time as fixes are backported to
older supported kernel versions.  The official CVE entry at
	https://cve.org/CVERecord/?id=CVE-2024-26957
will be updated if fixes are backported, please check that for the most
up to date information about this issue.

Affected files
==============

The file(s) affected by this issue are:
	drivers/s390/crypto/zcrypt_api.c

Mitigation
==========

The Linux kernel CVE team recommends that you update to the latest
stable kernel version for this, and many other bugfixes.  Individual
changes are never tested alone, but rather are part of a larger kernel
release.  Cherry-picking individual commits is not recommended or
supported by the Linux kernel community at all.  If however, updating to
the latest release is impossible, the individual changes to resolve this
issue can be found at these commits:
	https://git.kernel.org/stable/c/7e500849fa558879a1cde43f80c7c048c2437058
	https://git.kernel.org/stable/c/9daddee03de3f231012014dab8ab2b277a116a55
	https://git.kernel.org/stable/c/6470078ab3d8f222115e11c4ec67351f3031b3dd
	https://git.kernel.org/stable/c/a55677878b93e9ebc31f66d0e2fb93be5e7836a6
	https://git.kernel.org/stable/c/b7f6c3630eb3f103115ab0d7613588064f665d0d
	https://git.kernel.org/stable/c/a64ab862e84e3e698cd351a87cdb504c7fc575ca
	https://git.kernel.org/stable/c/befb7f889594d23e1b475720cf93efd2f77df000
	https://git.kernel.org/stable/c/394b6d8bbdf9ddee6d5bcf3e1f3e9f23eecd6484
	https://git.kernel.org/stable/c/50ed48c80fecbe17218afed4f8bed005c802976c