In the Linux kernel, the following vulnerability has been resolved:
dm thin: Use last transaction's pmd->root when commit failed
Recently we found a softlock up problem in dm thin pool btree lookup code due to corrupted metadata:
Kernel panic - not syncing: softlockup: hung tasks CPU: 7 PID: 2669225 Comm: kworker/u16:3 Hardware name: QEMU Standard PC (i440FX + PIIX, 1996) Workqueue: dm-thin doworker [dmthinpool] Call Trace: <IRQ> dumpstack+0x9c/0xd3 panic+0x35d/0x6b9 watchdogtimerfn.cold+0x16/0x25 runhrtimer+0xa2/0x2d0 </IRQ> RIP: 0010:relinklru+0x102/0x220 [dmbufio] _bufionew+0x11f/0x4f0 [dmbufio] newread+0xa3/0x1e0 [dmbufio] dmbmreadlock+0x33/0xd0 [dmpersistentdata] rostep+0x63/0x100 [dmpersistentdata] btreelookupraw.constprop.0+0x44/0x220 [dmpersistentdata] dmbtreelookup+0x16f/0x210 [dmpersistentdata] dmthinfindblock+0x12c/0x210 [dmthinpool] _processbioreadonly+0xc5/0x400 [dmthinpool] processthindeferredbios+0x1a4/0x4a0 [dmthinpool] processonework+0x3c5/0x730
Following process may generate a broken btree mixed with fresh and stale btree nodes, which could get dm thin trapped in an infinite loop while looking up data block: Transaction 1: pmd->root = A, A->B->C // One path in btree pmd->root = X, X->Y->Z // Copy-up Transaction 2: X,Z is updated on disk, Y write failed. // Commit failed, dm thin becomes read-only. processbioreadonly dmthinfindblock _findblock dmbtreelookup(pmd->root) The pmd->root points to a broken btree, Y may contain stale node pointing to any block, for example X, which gets dm thin trapped into a dead loop while looking up Z.
Fix this by setting pmd->root in _openmetadata(), so that dm thin will use the last transaction's pmd->root if commit failed.
Fetch a reproducer in [Link].
Linke: https://bugzilla.kernel.org/show_bug.cgi?id=216790
[
{
"target": {
"function": "__open_metadata",
"file": "drivers/md/dm-thin-metadata.c"
},
"id": "CVE-2022-50534-15119364",
"signature_type": "Function",
"signature_version": "v1",
"deprecated": false,
"source": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git@87d69b8824ca9b090f5a8ed47f758e8f6eecb871",
"digest": {
"function_hash": "317214377720489229783085366797562900571",
"length": 1546.0
}
},
{
"target": {
"file": "drivers/md/dm-thin-metadata.c"
},
"id": "CVE-2022-50534-31cdc383",
"signature_type": "Line",
"signature_version": "v1",
"deprecated": false,
"source": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git@b91f481300e3a10eaf66b94fc39b740928762aaf",
"digest": {
"threshold": 0.9,
"line_hashes": [
"229433128561273744954591760804291857500",
"170991969786588936387047963410677311106",
"337249623286969675281700392719465355825"
]
}
},
{
"target": {
"file": "drivers/md/dm-thin-metadata.c"
},
"id": "CVE-2022-50534-51e7ab6e",
"signature_type": "Line",
"signature_version": "v1",
"deprecated": false,
"source": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git@87d69b8824ca9b090f5a8ed47f758e8f6eecb871",
"digest": {
"threshold": 0.9,
"line_hashes": [
"229433128561273744954591760804291857500",
"170991969786588936387047963410677311106",
"337249623286969675281700392719465355825"
]
}
},
{
"target": {
"function": "__open_metadata",
"file": "drivers/md/dm-thin-metadata.c"
},
"id": "CVE-2022-50534-93d5c00e",
"signature_type": "Function",
"signature_version": "v1",
"deprecated": false,
"source": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git@b91f481300e3a10eaf66b94fc39b740928762aaf",
"digest": {
"function_hash": "317214377720489229783085366797562900571",
"length": 1546.0
}
}
]