CVE-2024-44976 ata: pata_macio: Fix DMA table overflow

2024-09-0419:54:28

Linux

www.cve.org

linux kernel

vulnerability resolved

pata_macio

dma table overflow

32-bit powermacs

fix

max_segment_size

page_size

commit

powermac

scsi core

default settings

bug

max_sectors_kb

distros

udev rules

sg_tablesize

EPSS

Percentile

9.6%

JSON

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

ata: pata_macio: Fix DMA table overflow

Kolbjørn and Jonáš reported that their 32-bit PowerMacs were crashing
in pata-macio since commit 09fe2bfa6b83 (“ata: pata_macio: Fix
max_segment_size with PAGE_SIZE == 64K”).

For example:

kernel BUG at drivers/ata/pata_macio.c:544!
Oops: Exception in kernel mode, sig: 5 [#1]
BE PAGE_SIZE=4K MMU=Hash SMP NR_CPUS=2 DEBUG_PAGEALLOC PowerMac
…
NIP pata_macio_qc_prep+0xf4/0x190
LR pata_macio_qc_prep+0xfc/0x190
Call Trace:
0xc1421660 (unreliable)
ata_qc_issue+0x14c/0x2d4
__ata_scsi_queuecmd+0x200/0x53c
ata_scsi_queuecmd+0x50/0xe0
scsi_queue_rq+0x788/0xb1c
__blk_mq_issue_directly+0x58/0xf4
blk_mq_plug_issue_direct+0x8c/0x1b4
blk_mq_flush_plug_list.part.0+0x584/0x5e0
__blk_flush_plug+0xf8/0x194
__submit_bio+0x1b8/0x2e0
submit_bio_noacct_nocheck+0x230/0x304
btrfs_work_helper+0x200/0x338
process_one_work+0x1a8/0x338
worker_thread+0x364/0x4c0
kthread+0x100/0x104
start_kernel_thread+0x10/0x14

That commit increased max_segment_size to 64KB, with the justification
that the SCSI core was already using that size when PAGE_SIZE == 64KB,
and that there was existing logic to split over-sized requests.

However with a sufficiently large request, the splitting logic causes
each sg to be split into two commands in the DMA table, leading to
overflow of the DMA table, triggering the BUG_ON().

With default settings the bug doesn’t trigger, because the request size
is limited by max_sectors_kb == 1280, however max_sectors_kb can be
increased, and apparently some distros do that by default using udev
rules.

Fix the bug for 4KB kernels by reverting to the old max_segment_size.

For 64KB kernels the sg_tablesize needs to be halved, to allow for the
possibility that each sg will be split into two.

CNA Affected

[
  {
    "product": "Linux",
    "vendor": "Linux",
    "defaultStatus": "unaffected",
    "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
    "programFiles": [
      "drivers/ata/pata_macio.c"
    ],
    "versions": [
      {
        "version": "09fe2bfa6b83",
        "lessThan": "709e4c8f78e1",
        "status": "affected",
        "versionType": "git"
      },
      {
        "version": "09fe2bfa6b83",
        "lessThan": "822c8020aebc",
        "status": "affected",
        "versionType": "git"
      }
    ]
  },
  {
    "product": "Linux",
    "vendor": "Linux",
    "defaultStatus": "affected",
    "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
    "programFiles": [
      "drivers/ata/pata_macio.c"
    ],
    "versions": [
      {
        "version": "6.10",
        "status": "affected"
      },
      {
        "version": "0",
        "lessThan": "6.10",
        "status": "unaffected",
        "versionType": "custom"
      },
      {
        "version": "6.10.7",
        "lessThanOrEqual": "6.10.*",
        "status": "unaffected",
        "versionType": "custom"
      },
      {
        "version": "6.11",
        "lessThanOrEqual": "*",
        "status": "unaffected",
        "versionType": "original_commit_for_fix"
      }
    ]
  }
]