CVE-2024-43874

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

crypto: ccp - Fix null pointer dereference in __sev_snp_shutdown_locked

Fix a null pointer dereference induced by DEBUG_TEST_DRIVER_REMOVE. Return from __sev_snp_shutdown_locked() if the psp_device or the sev_device structs are not initialized. Without the fix, the driver will produce the following splat:

ccp 0000:55:00.5: enabling device (0000 -> 0002) ccp 0000:55:00.5: sev enabled ccp 0000:55:00.5: psp enabled BUG: kernel NULL pointer dereference, address: 00000000000000f0 #PF: supervisor read access in kernel mode #PF: error_code(0x0000) - not-present page PGD 0 P4D 0 Oops: 0000 [#1] PREEMPT SMP DEBUG_PAGEALLOC NOPTI CPU: 262 PID: 1 Comm: swapper/0 Not tainted 6.9.0-rc1+ #29 RIP: 0010:__sev_snp_shutdown_locked+0x2e/0x150 Code: 00 55 48 89 e5 41 57 41 56 41 54 53 48 83 ec 10 41 89 f7 49 89 fe 65 48 8b 04 25 28 00 00 00 48 89 45 d8 48 8b 05 6a 5a 7f 06 <4c> 8b a0 f0 00 00 00 41 0f b6 9c 24 a2 00 00 00 48 83 fb 02 0f 83 RSP: 0018:ffffb2ea4014b7b8 EFLAGS: 00010286 RAX: 0000000000000000 RBX: ffff9e4acd2e0a28 RCX: 0000000000000000 RDX: 0000000000000000 RSI: 0000000000000000 RDI: ffffb2ea4014b808 RBP: ffffb2ea4014b7e8 R08: 0000000000000106 R09: 000000000003d9c0 R10: 0000000000000001 R11: ffffffffa39ff070 R12: ffff9e49d40590c8 R13: 0000000000000000 R14: ffffb2ea4014b808 R15: 0000000000000000 FS: 0000000000000000(0000) GS:ffff9e58b1e00000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 00000000000000f0 CR3: 0000000418a3e001 CR4: 0000000000770ef0 PKRU: 55555554 Call Trace: ? __die_body+0x6f/0xb0 ? __die+0xcc/0xf0 ? page_fault_oops+0x330/0x3a0 ? save_trace+0x2a5/0x360 ? do_user_addr_fault+0x583/0x630 ? exc_page_fault+0x81/0x120 ? asm_exc_page_fault+0x2b/0x30 ? __sev_snp_shutdown_locked+0x2e/0x150 __sev_firmware_shutdown+0x349/0x5b0 ? pm_runtime_barrier+0x66/0xe0 sev_dev_destroy+0x34/0xb0 psp_dev_destroy+0x27/0x60 sp_destroy+0x39/0x90 sp_pci_remove+0x22/0x60 pci_device_remove+0x4e/0x110 really_probe+0x271/0x4e0 __driver_probe_device+0x8f/0x160 driver_probe_device+0x24/0x120 __driver_attach+0xc7/0x280 ? driver_attach+0x30/0x30 bus_for_each_dev+0x10d/0x130 driver_attach+0x22/0x30 bus_add_driver+0x171/0x2b0 ? unaccepted_memory_init_kdump+0x20/0x20 driver_register+0x67/0x100 __pci_register_driver+0x83/0x90 sp_pci_init+0x22/0x30 sp_mod_init+0x13/0x30 do_one_initcall+0xb8/0x290 ? sched_clock_noinstr+0xd/0x10 ? local_clock_noinstr+0x3e/0x100 ? stack_depot_save_flags+0x21e/0x6a0 ? local_clock+0x1c/0x60 ? stack_depot_save_flags+0x21e/0x6a0 ? sched_clock_noinstr+0xd/0x10 ? local_clock_noinstr+0x3e/0x100 ? __lock_acquire+0xd90/0xe30 ? sched_clock_noinstr+0xd/0x10 ? local_clock_noinstr+0x3e/0x100 ? __create_object+0x66/0x100 ? local_clock+0x1c/0x60 ? __create_object+0x66/0x100 ? parameq+0x1b/0x90 ? parse_one+0x6d/0x1d0 ? parse_args+0xd7/0x1f0 ? do_initcall_level+0x180/0x180 do_initcall_level+0xb0/0x180 do_initcalls+0x60/0xa0 ? kernel_init+0x1f/0x1d0 do_basic_setup+0x41/0x50 kernel_init_freeable+0x1ac/0x230 ? rest_init+0x1f0/0x1f0 kernel_init+0x1f/0x1d0 ? rest_init+0x1f0/0x1f0 ret_from_fork+0x3d/0x50 ? rest_init+0x1f0/0x1f0 ret_from_fork_asm+0x11/0x20 Modules linked in: CR2: 00000000000000f0 —[ end trace 0000000000000000 ]— RIP: 0010:__sev_snp_shutdown_locked+0x2e/0x150 Code: 00 55 48 89 e5 41 57 41 56 41 54 53 48 83 ec 10 41 89 f7 49 89 fe 65 48 8b 04 25 28 00 00 00 48 89 45 d8 48 8b 05 6a 5a 7f 06 <4c> 8b a0 f0 00 00 00 41 0f b6 9c 24 a2 00 00 00 48 83 fb 02 0f 83 RSP: 0018:ffffb2ea4014b7b8 EFLAGS: 00010286 RAX: 0000000000000000 RBX: ffff9e4acd2e0a28 RCX: 0000000000000000 RDX: 0000000 —truncated—

Weakness

A NULL pointer dereference occurs when the application dereferences a pointer that it expects to be valid, but is NULL, typically causing a crash or exit.

Affected Software

Potential Mitigations

References

• https://git.kernel.org/stable/c/468e3295774d0edce15f4ae475913b5076dd4f40
• https://git.kernel.org/stable/c/bbf2c94503f6a421ed9b79e300d8085810da765d