CVE-2024-26957

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:

---truncated---