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CVE-2026-92501

Vulnérabilité non évaluée dans Linux (Linux)

CVSS 0.0 · Non évaluée
EPSS 0.2%
Linux•Linux•Versions : <4e4e3eec506247c8f8bd8aaa1eb25e67016681a5, <=6.1.*, <15cdefd0c0522f9d5e12d947fa04f4c11649b699, <=6.12.*, <74eee4ff9698a65b2e6e15dac0e50d6526ad5f20, 5.15.221, 5.10.270, 0, 6.1.188, 6.18.52, <d47cdadd6e49023f7ee248048463807f1214f1ee, <fd7e0dab20837b9ea1eeef7c26f78ace8ac8258c, <=5.10.*, <=6.6.*, 6.6.157, 7.2.6, <f0af3ae09fb72382da1a5371bf6761b0264668e4, <5.5, <=6.18.*, 5.5, 6.12.110, <=7.2.*, <7341e234927ff215f1d5d0bcfe04b74f53af378d, <9fd3ffc3c51c9deaba99bd7b338fff2d08f52416, <=*, 378f32bab3714f04c4e0c3aee4129f6703805550, <=5.15.*, 7.3

Description

In the Linux kernel, the following vulnerability has been resolved: ext4: drain in-flight DIO before buffered write fallback generic/746 started failing intermittently on ext3 (no-extent inodes). The test triggers 'Page cache invalidation failure on direct I/O' warnings and subsequent fsync returns -EIO. Adding a 50ms delay between ext4_buffered_write_iter() and filemap_write_and_wait_range() in ext4_dio_write_iter() makes the race almost always reproducible. On no-extent inodes, DIO writes to holes cannot use unwritten extents, so ext4_iomap_alloc() leaves m_flags=0 and ext4_map_blocks() returns 0. The iomap layer then returns -ENOTBLK, causing fallback to buffered I/O. The fallback path in ext4_dio_write_iter() calls ext4_buffered_write_iter() which dirties pages, then does flush and invalidate. However, there's an unprotected window between ext4_buffered_write_iter() returning (with inode lock released) and the subsequent flush+invalidate. Concurrent async DIO completions from other threads can run kiocb_invalidate_post_direct_write() during this window. If pages have been re-dirtied, post-invalidation finds dirty pages and triggers the warning, setting -EIO in the error sequence. Consider a file with two 4k extents: [hole][written]. Thread A does DIO to the written extent, while thread B does DIO spanning both: kworker A (4k DIO, allocated block) kworker B (8k DIO, fallback) ----------------------------------- ---------------------------- inode_lock_shared() inode_lock_shared() iomap_dio_rw(): iomap_dio_rw(): kiocb_invalidate_pages -> clean iomap_begin -> -ENOTBLK submit_bio (async) dio->size = 0 inode_unlock_shared() inode_unlock_shared() [bio pending in block layer] /* fallback: lock released */ ext4_buffered_write_iter() inode_lock(exclusive) generic_perform_write() -> dirty pages [0, 8k] inode_unlock(exclusive) /* pages dirty, no lock */ [bio completes] filemap_write_and_wait_range() iomap_dio_complete() -> flush dirty pages kiocb_invalidate_post_direct_write() invalidate_mapping_pages() invalidate_inode_pages2_range() -> finds dirty page! -> dio_warn_stale_pagecache() -> errseq_set(-EIO) This issue can be triggered through normal I/O paths, not just intentionally overlapping DIO writes from userspace. For example, generic/746 uses a loop device where multiple kworkers issue concurrent I/O to the backing file. Additionally, when block_size < folio_size, non-overlapping DIO writes that share a large folio can also trigger the race. Add inode_dio_wait() in ext4_buffered_write_iter() before ext4_write_checks() to drain all in-flight DIO. This ensures that all DIO clears existing pages before submitting IO (via kiocb_invalidate_pages()), all BIO waits for all DIO to complete (via inode_dio_wait()), and ext4_write_checks() observes the inode size after all completed DIO so that ext4_block_zero_eof() does not race with in-flight DIO, thus eliminating the race.

Gravité et risque d'exploitation

CVE-2026-92501 obtient un score CVSS de 0.0/10, soit une gravité non évaluée. Selon le modèle EPSS, la probabilité qu'elle soit exploitée dans les 30 prochains jours est de 0.18 %, ce qui la place devant 6.8 % des CVE référencées.

Que faire ?

  • Vérifiez si Linux (versions <4e4e3eec506247c8f8bd8aaa1eb25e67016681a5, <=6.1.*, <15cdefd0c0522f9d5e12d947fa04f4c11649b699, <=6.12.*, <74eee4ff9698a65b2e6e15dac0e50d6526ad5f20, 5.15.221, 5.10.270, 0, 6.1.188, 6.18.52, <d47cdadd6e49023f7ee248048463807f1214f1ee, <fd7e0dab20837b9ea1eeef7c26f78ace8ac8258c, <=5.10.*, <=6.6.*, 6.6.157, 7.2.6, <f0af3ae09fb72382da1a5371bf6761b0264668e4, <5.5, <=6.18.*, 5.5, 6.12.110, <=7.2.*, <7341e234927ff215f1d5d0bcfe04b74f53af378d, <9fd3ffc3c51c9deaba99bd7b338fff2d08f52416, <=*, 378f32bab3714f04c4e0c3aee4129f6703805550, <=5.15.*, 7.3) est présent sur votre parc.
  • Appliquez le correctif ou la version corrigée indiqués dans les références de l'éditeur.
  • À défaut de correctif, limitez l'exposition (filtrage réseau, désactivation du composant).
  • Automatisez la détection : les agents CVE Heimdall (gratuits, open source) corrèlent l'inventaire de vos serveurs avec la base CVE.

Références

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