FKIE_CVE-2026-31715
Vulnerability from fkie_nvd - Published: 2026-05-01 14:16 - Updated: 2026-05-07 06:16
Severity ?
Summary
In the Linux kernel, the following vulnerability has been resolved:
f2fs: fix UAF caused by decrementing sbi->nr_pages[] in f2fs_write_end_io()
The xfstests case "generic/107" and syzbot have both reported a NULL
pointer dereference.
The concurrent scenario that triggers the panic is as follows:
F2FS_WB_CP_DATA write callback umount
- f2fs_write_checkpoint
- f2fs_wait_on_all_pages(sbi, F2FS_WB_CP_DATA)
- blk_mq_end_request
- bio_endio
- f2fs_write_end_io
: dec_page_count(sbi, F2FS_WB_CP_DATA)
: wake_up(&sbi->cp_wait)
- kill_f2fs_super
- kill_block_super
- f2fs_put_super
: iput(sbi->node_inode)
: sbi->node_inode = NULL
: f2fs_in_warm_node_list
- is_node_folio // sbi->node_inode is NULL and panic
The root cause is that f2fs_put_super() calls iput(sbi->node_inode) and
sets sbi->node_inode to NULL after sbi->nr_pages[F2FS_WB_CP_DATA] is
decremented to zero. As a result, f2fs_in_warm_node_list() may
dereference a NULL node_inode when checking whether a folio belongs to
the node inode, leading to a panic.
This patch fixes the issue by calling f2fs_in_warm_node_list() before
decrementing sbi->nr_pages[F2FS_WB_CP_DATA], thus preventing the
use-after-free condition.
References
Impacted products
| Vendor | Product | Version | |
|---|---|---|---|
| linux | linux_kernel | * | |
| linux | linux_kernel | * | |
| linux | linux_kernel | 7.1 |
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"descriptions": [
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"lang": "en",
"value": "In the Linux kernel, the following vulnerability has been resolved:\n\nf2fs: fix UAF caused by decrementing sbi-\u003enr_pages[] in f2fs_write_end_io()\n\nThe xfstests case \"generic/107\" and syzbot have both reported a NULL\npointer dereference.\n\nThe concurrent scenario that triggers the panic is as follows:\n\nF2FS_WB_CP_DATA write callback umount\n - f2fs_write_checkpoint\n - f2fs_wait_on_all_pages(sbi, F2FS_WB_CP_DATA)\n- blk_mq_end_request\n - bio_endio\n - f2fs_write_end_io\n : dec_page_count(sbi, F2FS_WB_CP_DATA)\n : wake_up(\u0026sbi-\u003ecp_wait)\n - kill_f2fs_super\n - kill_block_super\n - f2fs_put_super\n : iput(sbi-\u003enode_inode)\n : sbi-\u003enode_inode = NULL\n : f2fs_in_warm_node_list\n - is_node_folio // sbi-\u003enode_inode is NULL and panic\n\nThe root cause is that f2fs_put_super() calls iput(sbi-\u003enode_inode) and\nsets sbi-\u003enode_inode to NULL after sbi-\u003enr_pages[F2FS_WB_CP_DATA] is\ndecremented to zero. As a result, f2fs_in_warm_node_list() may\ndereference a NULL node_inode when checking whether a folio belongs to\nthe node inode, leading to a panic.\n\nThis patch fixes the issue by calling f2fs_in_warm_node_list() before\ndecrementing sbi-\u003enr_pages[F2FS_WB_CP_DATA], thus preventing the\nuse-after-free condition."
}
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"id": "CVE-2026-31715",
"lastModified": "2026-05-07T06:16:04.013",
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"attackComplexity": "LOW",
"attackVector": "LOCAL",
"availabilityImpact": "HIGH",
"baseScore": 7.8,
"baseSeverity": "HIGH",
"confidentialityImpact": "HIGH",
"integrityImpact": "HIGH",
"privilegesRequired": "LOW",
"scope": "UNCHANGED",
"userInteraction": "NONE",
"vectorString": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H",
"version": "3.1"
},
"exploitabilityScore": 1.8,
"impactScore": 5.9,
"source": "nvd@nist.gov",
"type": "Primary"
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"published": "2026-05-01T14:16:21.637",
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Experimental. This forecast is provided for visualization only and may change without notice. Do not use it for operational decisions.
Forecast uses a logistic model when the trend is rising, or an exponential decay model when the trend is falling. Fitted via linearized least squares.
Sightings
| Author | Source | Type | Date | Other |
|---|
Nomenclature
- Seen: The vulnerability was mentioned, discussed, or observed by the user.
- Confirmed: The vulnerability has been validated from an analyst's perspective.
- Published Proof of Concept: A public proof of concept is available for this vulnerability.
- Exploited: The vulnerability was observed as exploited by the user who reported the sighting.
- Patched: The vulnerability was observed as successfully patched by the user who reported the sighting.
- Not exploited: The vulnerability was not observed as exploited by the user who reported the sighting.
- Not confirmed: The user expressed doubt about the validity of the vulnerability.
- Not patched: The vulnerability was not observed as successfully patched by the user who reported the sighting.
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