GHSA-FH88-V2MJ-CP79
Vulnerability from github – Published: 2024-10-21 15:32 – Updated: 2026-07-14 15:31In the Linux kernel, the following vulnerability has been resolved:
erofs: handle overlapped pclusters out of crafted images properly
syzbot reported a task hang issue due to a deadlock case where it is waiting for the folio lock of a cached folio that will be used for cache I/Os.
After looking into the crafted fuzzed image, I found it's formed with several overlapped big pclusters as below:
Ext: logical offset | length : physical offset | length 0: 0.. 16384 | 16384 : 151552.. 167936 | 16384 1: 16384.. 32768 | 16384 : 155648.. 172032 | 16384 2: 32768.. 49152 | 16384 : 537223168.. 537239552 | 16384 ...
Here, extent 0/1 are physically overlapped although it's entirely impossible for normal filesystem images generated by mkfs.
First, managed folios containing compressed data will be marked as up-to-date and then unlocked immediately (unlike in-place folios) when compressed I/Os are complete. If physical blocks are not submitted in the incremental order, there should be separate BIOs to avoid dependency issues. However, the current code mis-arranges z_erofs_fill_bio_vec() and BIO submission which causes unexpected BIO waits.
Second, managed folios will be connected to their own pclusters for efficient inter-queries. However, this is somewhat hard to implement easily if overlapped big pclusters exist. Again, these only appear in fuzzed images so let's simply fall back to temporary short-lived pages for correctness.
Additionally, it justifies that referenced managed folios cannot be
truncated for now and reverts part of commit 2080ca1ed3e4 ("erofs: tidy
up struct z_erofs_bvec") for simplicity although it shouldn't be any
difference.
{
"affected": [],
"aliases": [
"CVE-2024-47736"
],
"database_specific": {
"cwe_ids": [
"CWE-667"
],
"github_reviewed": false,
"github_reviewed_at": null,
"nvd_published_at": "2024-10-21T13:15:03Z",
"severity": "MODERATE"
},
"details": "In the Linux kernel, the following vulnerability has been resolved:\n\nerofs: handle overlapped pclusters out of crafted images properly\n\nsyzbot reported a task hang issue due to a deadlock case where it is\nwaiting for the folio lock of a cached folio that will be used for\ncache I/Os.\n\nAfter looking into the crafted fuzzed image, I found it\u0027s formed with\nseveral overlapped big pclusters as below:\n\n Ext: logical offset | length : physical offset | length\n 0: 0.. 16384 | 16384 : 151552.. 167936 | 16384\n 1: 16384.. 32768 | 16384 : 155648.. 172032 | 16384\n 2: 32768.. 49152 | 16384 : 537223168.. 537239552 | 16384\n...\n\nHere, extent 0/1 are physically overlapped although it\u0027s entirely\n_impossible_ for normal filesystem images generated by mkfs.\n\nFirst, managed folios containing compressed data will be marked as\nup-to-date and then unlocked immediately (unlike in-place folios) when\ncompressed I/Os are complete. If physical blocks are not submitted in\nthe incremental order, there should be separate BIOs to avoid dependency\nissues. However, the current code mis-arranges z_erofs_fill_bio_vec()\nand BIO submission which causes unexpected BIO waits.\n\nSecond, managed folios will be connected to their own pclusters for\nefficient inter-queries. However, this is somewhat hard to implement\neasily if overlapped big pclusters exist. Again, these only appear in\nfuzzed images so let\u0027s simply fall back to temporary short-lived pages\nfor correctness.\n\nAdditionally, it justifies that referenced managed folios cannot be\ntruncated for now and reverts part of commit 2080ca1ed3e4 (\"erofs: tidy\nup `struct z_erofs_bvec`\") for simplicity although it shouldn\u0027t be any\ndifference.",
"id": "GHSA-fh88-v2mj-cp79",
"modified": "2026-07-14T15:31:15Z",
"published": "2024-10-21T15:32:26Z",
"references": [
{
"type": "ADVISORY",
"url": "https://nvd.nist.gov/vuln/detail/CVE-2024-47736"
},
{
"type": "WEB",
"url": "https://cert-portal.siemens.com/productcert/html/ssa-019113.html"
},
{
"type": "WEB",
"url": "https://cert-portal.siemens.com/productcert/html/ssa-082556.html"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/1bf7e414cac303c9aec1be67872e19be8b64980c"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/9cfa199bcbbbba31cbf97b2786f44f4464f3f29a"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/9e2f9d34dd12e6e5b244ec488bcebd0c2d566c50"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/b9b30af0e86ffb485301ecd83b9129c9dfb7ebf8"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/c1172e65aad4b115392ea4c6e61e56e5b9b69df4"
}
],
"schema_version": "1.4.0",
"severity": [
{
"score": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H",
"type": "CVSS_V3"
}
]
}
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