CVE-2026-31715: Linux kernel · f2fs: fix UAF caused by decrementing sbi->nr_pages[] in f2fs_write_end_io()
Affects Linux kernelSource GCVE Database
Not known to be exploited.
Data as of 11 Nov 2026, 23:24 UTC
Rated by Threat Radar · No CVSS score from NVD or the CNA
Thin evidence
One scorer or none- EPSS
- 0.1% chance of exploitation in 30 days – higher than 1% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.
Exploitation evidence
Disclosed: evidence found.
CVE published 1 May 2026
Detectable: no evidence on record.
No public nuclei template indexed
Weaponized: no evidence on record.
No public exploit code indexed in Metasploit or Exploit-DB
Exploited in the wildExploited: no evidence on record.
Not in CISA KEV and no source reports exploitation
Observed by OffSeq MirageSeen by Mirage: no evidence on record.
No attack traffic recorded by OffSeq Mirage sensors
A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), the Metasploit, Exploit-DB and nuclei-templates index as of 11 Nov 2026.
Description
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
- git.kernel.org/stable/c/7dbdab4430e4654db9aacef12b9b3b8b29ca25cb (opens in a new tab)
- git.kernel.org/stable/c/ffb94770dbdfb5411be5d9f44a960b010ec890ad (opens in a new tab)
- git.kernel.org/stable/c/0d40b26377f891e6dcb6efaf8ef9374c99be1b1d (opens in a new tab)
- git.kernel.org/stable/c/1171f329cf1c175321251ac40fd126150d7ad1e8 (opens in a new tab)
- git.kernel.org/stable/c/7be222de96c0f9eee6e65eeb017ef855ee185cfa (opens in a new tab)
- git.kernel.org/stable/c/963d2e24d9d92a31e6773b0f642214f10013ebf7 (opens in a new tab)
- git.kernel.org/stable/c/188bb65f247a7a7c62f287c9a263aee3cad96fa5 (opens in a new tab)
- git.kernel.org/stable/c/2d9c4a4ed4eef1f82c5b16b037aee8bad819fd53 (opens in a new tab)