CVE-2026-80734
Estado: RecibidaAlta (8.8)—
In the Linux kernel, the following vulnerability has been resolved:
btrfs: initialize inode mapping flags for cached inodes
[BUG] When running generic/795 with 8K block size, 4K page size, the test always fails, triggering some ASSERT()s related to folio size:
The ASSERT() itself is added by a later patch. The crash is triggered with that new debug patch, and without this fix.
[CAUSE] In the above case, the start 16826368 is properly 8K aligned, but the end (16830463 + 1) is not 8K aligned. Furthermore the mapping's minimal folio order is 0, not the expected 1 for 8K block size with 4K page size.
So this means some inodes do not have btrfs_set_inode_mapping_order() called on it.
Leer descripción completaMostrar menos
The missing btrfs_set_inode_mapping_order() call happens for cached inodes, through the following events:
- btrfs_iget() for inode X called again
Thus later page cache read will get a folio whose size is smaller than block size, as the mapping has its minimal folio order set as 0 not 1, then trigger the ASSERT().
[FIX] Move the btrfs_update_inode_mapping_flags() and btrfs_set_inode_mapping_order() calls under cache_index label, so that the mapping flags and minimal folio order is always set no matter if we have a cached inode.
Detalles técnicos trazas, registros y código del informe original
795 (241074): drop_caches: 3
assertion failed: IS_ALIGNED(start, blocksize) && IS_ALIGNED(end + 1, blocksize), in extent_io.c:1404 (blocksize=8192 root=262 ino=258 start=16826368 end=16830463 mapping min order=0)
------------[ cut here ]------------
kernel BUG at extent_io.c:1404!
Oops: invalid opcode: 0000 [#1] SMP
CPU: 8 UID: 0 PID: 241105 Comm: fsstress Tainted: G OE 7.2.0-rc5-custom+ #442 PREEMPT(full) f4bfb352566f3949f29c233ce6f735050a03b245
Tainted: [O]=OOT_MODULE, [E]=UNSIGNED_MODULE
Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS unknown 02/02/2022
RIP: 0010:assert_folio_range.cold+0x3d/0x3f [btrfs]
Call Trace:
<TASK>
btrfs_read_folio+0x9e/0x170 [btrfs 4cd1dd93b341b8ef766643f9512f4a86259567a3]
prepare_one_folio.constprop.0+0x104/0x2a0 [btrfs 4cd1dd93b341b8ef766643f9512f4a86259567a3]
btrfs_buffered_write+0x285/0xa50 [btrfs 4cd1dd93b341b8ef766643f9512f4a86259567a3]
btrfs_do_write_iter+0x1aa/0x210 [btrfs 4cd1dd93b341b8ef766643f9512f4a86259567a3]
iter_file_splice_write+0x31a/0x540
direct_splice_actor+0x53/0x170
splice_direct_to_actor+0xe9/0x240
do_splice_direct+0x76/0xb0
vfs_copy_file_range+0x1fd/0x630
__x64_sys_copy_file_range+0xf9/0x220
do_syscall_64+0xe1/0x790
entry_SYSCALL_64_after_hwframe+0x4b/0x53
</TASK>
---[ end trace 0000000000000000 ]---
- btrfs_create_new_inode() called for inode X
Which properly sets minimal folio order for the VFS inode.
- btrfs_update_inode() called for inode X
Which calls btrfs_delayed_update_inode() to create a delayed_node
into root->delayed_nodes xarray.
- Drop cache/memory pressure, evicting in-memory inode X
Which evicted the inode X, but delayed_node is still in
root->delayed_nodes for future reuse.
btrfs_iget()
|- btrfs_iget_locked()
| |- iget5_locked_rcu()
| Which creates a new vfs_inode for btrfs, whose mapping still
| has the minimal order as 0.
|
|- btrfs_read_locked_inode()
|- btrfs_fill_inode()
| |- btrfs_get_delayed_node()
| Which found out the previous node, and use that delayed
| node to initialize the new inode.
|
|- filled = true;
|- if (filled) goto cache_index;
Which skips the btrfs_update_inode_mapping_flags() and
btrfs_set_inode_mapping_order() calls.
So the inode still has minimal folio order set as 0, not
the required 1.CVSS
- Versión: 3.1
- Vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
- Puntuación base: 8.8
Probabilidad de explotación (EPSS)
- Probabilidad de explotación en los próximos 30 días: 0.51%
- Percentil entre todas las CVEs puntuadas: 41
- Fecha de la puntuación: 6/10/2026
EPSS (Exploit Prediction Scoring System, de FIRST) estima la probabilidad de que una vulnerabilidad sea explotada en 30 días. Complementa a CVSS (impacto) y a CISA KEV (explotación confirmada).
🎯 Técnicas ATT&CK
Cómo se explota esta vulnerabilidad y qué consigue el atacante, en el lenguaje de MITRE ATT&CK.
- Explotación
T1210Exploitation of Remote Serviceslateral movement25 % - Impacto principal
T1499.004Application or System Exploitationimpact45 % - Impacto secundario
T1565.001Stored Data Manipulationimpact35 %
Vector CVSS:3.1/AV:N/AC:L/PR:L sugiere T1210, pero el CVE es un bug de inicialización de kernel sin explotación activa documentada. Los impactos son corrupción de datos y DoS por lecturas de folio desalineadas.
Inferido por nuestro agente de análisis a partir de la descripción oficial, el vector CVSS y la CWE, y comprobado por un supervisor. Puede contener errores.
🛡️ Mitigaciones ATT&CK que cubren estas técnicas
Tecnologías afectadas (1)
⚠ Inferidas por IA a partir de la descripción — NVD aún no ha analizado esta CVE; no son CPE verificados.
Referencias
JSON original (NVD)
Mostrar
{
"id": "CVE-2026-80734",
"cveTags": [],
"metrics": {
"cvssMetricV31": [
{
"type": "Secondary",
"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
"cvssData": {
"scope": "UNCHANGED",
"version": "3.1",
"baseScore": 8.8,
"attackVector": "NETWORK",
"baseSeverity": "HIGH",
"vectorString": "CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H",
"integrityImpact": "HIGH",
"userInteraction": "NONE",
"attackComplexity": "LOW",
"availabilityImpact": "HIGH",
"privilegesRequired": "LOW",
"confidentialityImpact": "HIGH"
},
"impactScore": 5.9,
"exploitabilityScore": 2.8
}
]
},
"affected": [
{
"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
"affectedData": [
{
"repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
"vendor": "Linux",
"product": "Linux",
"versions": [
{
"status": "affected",
"version": "ecde48a1a6b3256bd49db8780bf37556b157783c",
"lessThan": "0d26249671171ab759cb4fdce673554a690fa655",
"versionType": "git"
},
{
"status": "affected",
"version": "ecde48a1a6b3256bd49db8780bf37556b157783c",
"lessThan": "0ef349734a93227b45f65fc50a3311d1cc5f03e9",
"versionType": "git"
},
{
"status": "affected",
"version": "01b002151539a4c2b27bfff9af033329a9b659e7",
"versionType": "git"
},
{
"status": "affected",
"version": "ae584726e6eddf6cfbe49b3f4a78b3197716b6f8",
"versionType": "git"
},
{
"status": "affected",
"version": "6.12.111",
"lessThan": "6.13",
"versionType": "semver"
},
{
"status": "affected",
"version": "6.14.6",
"lessThan": "6.15",
"versionType": "semver"
}
],
"programFiles": [
"fs/btrfs/inode.c"
],
"defaultStatus": "unaffected"
},
{
"repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
"vendor": "Linux",
"product": "Linux",
"versions": [
{
"status": "affected",
"version": "6.15"
},
{
"status": "unaffected",
"version": "0",
"lessThan": "6.15",
"versionType": "semver"
},
{
"status": "unaffected",
"version": "7.1.9",
"versionType": "semver",
"lessThanOrEqual": "7.1.*"
},
{
"status": "unaffected",
"version": "7.2",
"versionType": "original_commit_for_fix",
"lessThanOrEqual": "*"
}
],
"programFiles": [
"fs/btrfs/inode.c"
],
"defaultStatus": "affected"
}
]
}
],
"published": "2026-09-03T13:06:12.200",
"references": [
{
"url": "https://git.kernel.org/stable/c/0d26249671171ab759cb4fdce673554a690fa655",
"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
},
{
"url": "https://git.kernel.org/stable/c/0ef349734a93227b45f65fc50a3311d1cc5f03e9",
"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
}
],
"vulnStatus": "Received",
"descriptions": [
{
"lang": "en",
"value": "In the Linux kernel, the following vulnerability has been resolved:\n\nbtrfs: initialize inode mapping flags for cached inodes\n\n[BUG]\nWhen running generic/795 with 8K block size, 4K page size, the test\nalways fails, triggering some ASSERT()s related to folio size:\n\n 795 (241074): drop_caches: 3\n assertion failed: IS_ALIGNED(start, blocksize) && IS_ALIGNED(end + 1, blocksize), in extent_io.c:1404 (blocksize=8192 root=262 ino=258 start=16826368 end=16830463 mapping min order=0)\n ------------[ cut here ]------------\n kernel BUG at extent_io.c:1404!\n Oops: invalid opcode: 0000 [#1] SMP\n CPU: 8 UID: 0 PID: 241105 Comm: fsstress Tainted: G OE 7.2.0-rc5-custom+ #442 PREEMPT(full) f4bfb352566f3949f29c233ce6f735050a03b245\n Tainted: [O]=OOT_MODULE, [E]=UNSIGNED_MODULE\n Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS unknown 02/02/2022\n RIP: 0010:assert_folio_range.cold+0x3d/0x3f [btrfs]\n Call Trace:\n <TASK>\n btrfs_read_folio+0x9e/0x170 [btrfs 4cd1dd93b341b8ef766643f9512f4a86259567a3]\n prepare_one_folio.constprop.0+0x104/0x2a0 [btrfs 4cd1dd93b341b8ef766643f9512f4a86259567a3]\n btrfs_buffered_write+0x285/0xa50 [btrfs 4cd1dd93b341b8ef766643f9512f4a86259567a3]\n btrfs_do_write_iter+0x1aa/0x210 [btrfs 4cd1dd93b341b8ef766643f9512f4a86259567a3]\n iter_file_splice_write+0x31a/0x540\n direct_splice_actor+0x53/0x170\n splice_direct_to_actor+0xe9/0x240\n do_splice_direct+0x76/0xb0\n vfs_copy_file_range+0x1fd/0x630\n __x64_sys_copy_file_range+0xf9/0x220\n do_syscall_64+0xe1/0x790\n entry_SYSCALL_64_after_hwframe+0x4b/0x53\n </TASK>\n ---[ end trace 0000000000000000 ]---\n\nThe ASSERT() itself is added by a later patch.\nThe crash is triggered with that new debug patch, and without this fix.\n\n[CAUSE]\nIn the above case, the start 16826368 is properly 8K aligned, but the\nend (16830463 + 1) is not 8K aligned.\nFurthermore the mapping's minimal folio order is 0, not the expected 1\nfor 8K block size with 4K page size.\n\nSo this means some inodes do not have btrfs_set_inode_mapping_order()\ncalled on it.\n\nThe missing btrfs_set_inode_mapping_order() call happens for cached\ninodes, through the following events:\n\n- btrfs_create_new_inode() called for inode X\n Which properly sets minimal folio order for the VFS inode.\n\n- btrfs_update_inode() called for inode X\n Which calls btrfs_delayed_update_inode() to create a delayed_node\n into root->delayed_nodes xarray.\n\n- Drop cache/memory pressure, evicting in-memory inode X\n Which evicted the inode X, but delayed_node is still in\n root->delayed_nodes for future reuse.\n\n- btrfs_iget() for inode X called again\n\n btrfs_iget()\n |- btrfs_iget_locked()\n | |- iget5_locked_rcu()\n | Which creates a new vfs_inode for btrfs, whose mapping still\n | has the minimal order as 0.\n |\n |- btrfs_read_locked_inode()\n |- btrfs_fill_inode()\n | |- btrfs_get_delayed_node()\n | Which found out the previous node, and use that delayed\n | node to initialize the new inode.\n |\n |- filled = true;\n |- if (filled) goto cache_index;\n Which skips the btrfs_update_inode_mapping_flags() and\n\tbtrfs_set_inode_mapping_order() calls.\n\tSo the inode still has minimal folio order set as 0, not\n\tthe required 1.\n\nThus later page cache read will get a folio whose size is smaller than\nblock size, as the mapping has its minimal folio order set as 0 not 1,\nthen trigger the ASSERT().\n\n[FIX]\nMove the btrfs_update_inode_mapping_flags() and\nbtrfs_set_inode_mapping_order() calls under cache_index label,\nso that the mapping flags and minimal folio order is always set\nno matter if we have a cached inode."
}
],
"lastModified": "2026-09-21T14:17:20.520",
"sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
}