CVE-2024-44976

published 2024-09-04

CVE-2024-44976: 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…

Priority P4 22 medium 5.5 CVSS 3.1

AV L AC L PR L UI N S U C N I N A H

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.

Affected

8 ranges

Vendor	Product	Version range	Fixed in
debian	linux	< linux 6.10.7-1 (forky)	linux 6.10.7-1 (forky)
linux	linux	—	—
linux	linux	>= 09fe2bfa6b83f865126ce3964744863f69a4a030 < 709e4c8f78e156ab332297bdd87527ec3da4e2d4	709e4c8f78e156ab332297bdd87527ec3da4e2d4
linux	linux	>= 09fe2bfa6b83f865126ce3964744863f69a4a030 < 822c8020aebcf5804a143b891e34f29873fee5e2	822c8020aebcf5804a143b891e34f29873fee5e2
linux	linux_kernel	—	—
linux	linux_kernel	>= 0 < 6.10.7-1	6.10.7-1
linux	linux_kernel	>= 0 < 6.10.7-1	6.10.7-1
linux	linux_kernel	>= 6.10 < 6.10.7	6.10.7

CVSS provenance

nvd v3.1 5.5 MEDIUM CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H

osv 5.5 MEDIUM

vendor_debian 5.5 LOW

vendor_redhat 5.5 MEDIUM

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