Affected: Linux

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: 00000…