CVE-2022-50647 RISC-V: Make port I/O string accessors actually work
A local attacker can trigger a kernel crash by accessing specific parallel port I/O operations on RISC-V systems.
- Exploited in the wild
- Not known
- Login needed
- Any signed-in user
- Attackable
- Local or same network only
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2022-50647?
CVE-2022-50647 is a denial of service vulnerability in Linux, published on 9 Dec 2025. It can only be exploited from the same machine or local network, with no action from the victim.
Official description
In the Linux kernel, the following vulnerability has been resolved:
RISC-V: Make port I/O string accessors actually work
Fix port I/O string accessors such as `insb', `outsb', etc. which use the physical PCI port I/O address rather than the corresponding memory mapping to get at the requested location, which in turn breaks at least accesses made by our parport driver to a PCIe parallel port such as:
PCI parallel port detected: 1415:c118, I/O at 0x1000(0x1008), IRQ 20 parport0: PC-style at 0x1000 (0x1008), irq 20, using FIFO [PCSPP,TRISTATE,COMPAT,EPP,ECP]
causing a memory access fault:
Unable to handle kernel access to user memory without uaccess routines at virtual address 0000000000001008 Oops [#1] Modules linked in: CPU: 1 PID: 350 Comm: cat Not tainted 6.0.0-rc2-00283-g10d4879f9ef0-dirty #23 Hardware name: SiFive HiFive Unmatched A00 (DT) epc : parport_pc_fifo_write_block_pio+0x266/0x416 ra : parport_pc_fifo_write_block_pio+0xb4/0x416 epc : ffffffff80542c3e ra : ffffffff80542a8c sp : ffffffd88899fc60 gp : ffffffff80fa2700 tp : ffffffd882b1e900 t0 : ffffffd883d0b000 t1 : ffffffffff000002 t2 : 4646393043330a38 s0 : ffffffd88899fcf0 s1 : 0000000000001000 a0 : 0000000000000010 a1 : 0000000000000000 a2 : ffffffd883d0a010 a3 : 0000000000000023 a4 : 00000000ffff8fbb a5 : ffffffd883d0a001 a6 : 0000000100000000 a7 : ffffffc800000000 s2 : ffffffffff000002 s3 : ffffffff80d28880 s4 : ffffffff80fa1f50 s5 : 0000000000001008 s6 : 0000000000000008 s7 : ffffffd883d0a000 s8 : 0004000000000000 s9 : ffffffff80dc1d80 s10: ffffffd8807e4000 s11: 0000000000000000 t3 : 00000000000000ff t4 : 393044410a303930 t5 : 0000000000001000 t6 : 0000000000040000 status: 0000000200000120 badaddr: 0000000000001008 cause: 000000000000000f [<ffffffff80543212>] parport_pc_compat_write_block_pio+0xfe/0x200 [<ffffffff8053bbc0>] parport_write+0x46/0xf8 [<ffffffff8050530e>] lp_write+0x158/0x2d2 [<ffffffff80185716>] vfs_write+0x8e/0x2c2 [<ffffffff80185a74>] ksys_write+0x52/0xc2 [<ffffffff80185af2>] sys_write+0xe/0x16 [<ffffffff80003770>] ret_from_syscall+0x0/0x2 ---[ end trace 0000000000000000 ]---
For simplicity address the problem by adding PCI_IOBASE to the physical address requested in the respective wrapper macros only, observing that the raw accessors such as `__insb', `__outsb', etc. are not supposed to be used other than by said macros. Remove the cast to `long' that is no longer needed on `addr' now that it is used as an offset from PCI_IOBASE and add parentheses around `addr' needed for predictable evaluation in macro expansion. No need to make said adjustments in separate changes given that current code is gravely broken and does not ever work.
Which versions are affected by CVE-2022-50647?
How do I fix CVE-2022-50647?
Apply the vendor's patch.
Upgrade, then put limits on request size, rate and nesting depth so one client cannot exhaust the service. More about Denial of service.
Is CVE-2022-50647 being exploited?
There is no known exploitation of CVE-2022-50647 in the wild and no public exploit code.
Sources
Also known as DEBIAN-CVE-2022-50647, GHSA-gvvr-vj5m-jq76, UBUNTU-CVE-2022-50647.