TLDRVuln - Cybersecurity Vulnerabilities Made Simple

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

comedi: comedi_8255: Correct error in subdevice initialization

The refactoring done in commit 5c57b1ccecc7 ("comedi: comedi_8255: Rework

subdevice initialization functions") to the initialization of the io

field of struct subdev_8255_private broke all cards using the

drivers/comedi/drivers/comedi_8255.c module.

Prior to 5c57b1ccecc7, __subdev_8255_init() initialized the io field

in the newly allocated struct subdev_8255_private to the non-NULL

callback given to the function, otherwise it used a flag parameter to

select between subdev_8255_mmio and subdev_8255_io. The refactoring

removed that logic and the flag, as subdev_8255_mm_init() and

subdev_8255_io_init() now explicitly pass subdev_8255_mmio and

subdev_8255_io respectively to __subdev_8255_init(), only

__subdev_8255_init() never sets spriv->io to the supplied

callback. That spriv->io is NULL leads to a later BUG:

BUG: kernel NULL pointer dereference, address: 0000000000000000

PGD 0 P4D 0

Oops: 0010 [#1] SMP PTI

CPU: 1 PID: 1210 Comm: systemd-udevd Not tainted 6.7.3-x86_64 #1

Hardware name: XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX

RIP: 0010:0x0

Code: Unable to access opcode bytes at 0xffffffffffffffd6.

RSP: 0018:ffffa3f1c02d7b78 EFLAGS: 00010202

RAX: 0000000000000000 RBX: ffff91f847aefd00 RCX: 000000000000009b

RDX: 0000000000000003 RSI: 0000000000000001 RDI: ffff91f840f6fc00

RBP: ffff91f840f6fc00 R08: 0000000000000000 R09: 0000000000000001

R10: 0000000000000000 R11: 000000000000005f R12: 0000000000000000

R13: 0000000000000000 R14: ffffffffc0102498 R15: ffff91f847ce6ba8

FS: 00007f72f4e8f500(0000) GS:ffff91f8d5c80000(0000) knlGS:0000000000000000

CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033

CR2: ffffffffffffffd6 CR3: 000000010540e000 CR4: 00000000000406f0

Call Trace:

<TASK>

? __die_body+0x15/0x57

? page_fault_oops+0x2ef/0x33c

? insert_vmap_area.constprop.0+0xb6/0xd5

? alloc_vmap_area+0x529/0x5ee

? exc_page_fault+0x15a/0x489

? asm_exc_page_fault+0x22/0x30

__subdev_8255_init+0x79/0x8d [comedi_8255]

pci_8255_auto_attach+0x11a/0x139 [8255_pci]

comedi_auto_config+0xac/0x117 [comedi]

? __pfx___driver_attach+0x10/0x10

pci_device_probe+0x88/0xf9

really_probe+0x101/0x248

__driver_probe_device+0xbb/0xed

driver_probe_device+0x1a/0x72

__driver_attach+0xd4/0xed

bus_for_each_dev+0x76/0xb8

bus_add_driver+0xbe/0x1be

driver_register+0x9a/0xd8

comedi_pci_driver_register+0x28/0x48 [comedi_pci]

? __pfx_pci_8255_driver_init+0x10/0x10 [8255_pci]

do_one_initcall+0x72/0x183

do_init_module+0x5b/0x1e8

init_module_from_file+0x86/0xac

__do_sys_finit_module+0x151/0x218

do_syscall_64+0x72/0xdb

entry_SYSCALL_64_after_hwframe+0x6e/0x76

RIP: 0033:0x7f72f50a0cb9

Code: ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 44 00 00 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 8b 0d 47 71 0c 00 f7 d8 64 89 01 48

RSP: 002b:00007ffd47e512d8 EFLAGS: 00000246 ORIG_RAX: 0000000000000139

RAX: ffffffffffffffda RBX: 0000562dd06ae070 RCX: 00007f72f50a0cb9

RDX: 0000000000000000 RSI: 00007f72f52d32df RDI: 000000000000000e

RBP: 0000000000000000 R08: 00007f72f5168b20 R09: 0000000000000000

R10: 0000000000000050 R11: 0000000000000246 R12: 00007f72f52d32df

R13: 0000000000020000 R14: 0000562dd06785c0 R15: 0000562dcfd0e9a8

</TASK>

Modules linked in: 8255_pci(+) comedi_8255 comedi_pci comedi intel_gtt e100(+) acpi_cpufreq rtc_cmos usbhid

CR2: 0000000000000000

---[ end trace 0000000000000000 ]---