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CVE-2021-47637

Vulnérabilité moyenne dans Linux (Linux)

CVSS 5.5 · Moyenne
EPSS 0.2%
Linux•Linux•Versions : 5.15.33, <=5.17.*, <70e9090acc32348cedc5def0cd6d5c126efc97b9, 5.18, <8b278c8dcfb565cb65eceb62a38cbf7a7c326db5, <9dddc8211430fb851ddf0b168e3a00c6f66cc185, 0, 9e0a1fff8db56eaaebb74b4a3ef65f86811c4798, <37bdf1ad592555ecda1d55b89f6e393e4c0589d1, <=5.10.*, <afd427048047e8efdedab30e8888044e2be5aa9c, 5.4.189, <=5.4.*, <4.9, <=4.19.*, 5.16.19, <c58af8564a7b08757173009030b74baf4b2b762b, <=5.16.*, <83e42a78428fc354f5e2049935b84c8d8d29b787, 5.10.110, 5.17.2, 4.9, 4.19.238, <=*, <=5.15.*

Description

In the Linux kernel, the following vulnerability has been resolved: ubifs: Fix deadlock in concurrent rename whiteout and inode writeback Following hung tasks: [ 77.028764] task:kworker/u8:4 state:D stack: 0 pid: 132 [ 77.028820] Call Trace: [ 77.029027] schedule+0x8c/0x1b0 [ 77.029067] mutex_lock+0x50/0x60 [ 77.029074] ubifs_write_inode+0x68/0x1f0 [ubifs] [ 77.029117] __writeback_single_inode+0x43c/0x570 [ 77.029128] writeback_sb_inodes+0x259/0x740 [ 77.029148] wb_writeback+0x107/0x4d0 [ 77.029163] wb_workfn+0x162/0x7b0 [ 92.390442] task:aa state:D stack: 0 pid: 1506 [ 92.390448] Call Trace: [ 92.390458] schedule+0x8c/0x1b0 [ 92.390461] wb_wait_for_completion+0x82/0xd0 [ 92.390469] __writeback_inodes_sb_nr+0xb2/0x110 [ 92.390472] writeback_inodes_sb_nr+0x14/0x20 [ 92.390476] ubifs_budget_space+0x705/0xdd0 [ubifs] [ 92.390503] do_rename.cold+0x7f/0x187 [ubifs] [ 92.390549] ubifs_rename+0x8b/0x180 [ubifs] [ 92.390571] vfs_rename+0xdb2/0x1170 [ 92.390580] do_renameat2+0x554/0x770 , are caused by concurrent rename whiteout and inode writeback processes: rename_whiteout(Thread 1) wb_workfn(Thread2) ubifs_rename do_rename lock_4_inodes (Hold ui_mutex) ubifs_budget_space make_free_space shrink_liability __writeback_inodes_sb_nr bdi_split_work_to_wbs (Queue new wb work) wb_do_writeback(wb work) __writeback_single_inode ubifs_write_inode LOCK(ui_mutex) ↑ wb_wait_for_completion (Wait wb work) <-- deadlock! Reproducer (Detail program in [Link]): 1. SYS_renameat2("/mp/dir/file", "/mp/dir/whiteout", RENAME_WHITEOUT) 2. Consume out of space before kernel(mdelay) doing budget for whiteout Fix it by doing whiteout space budget before locking ubifs inodes. BTW, it also fixes wrong goto tag 'out_release' in whiteout budget error handling path(It should at least recover dir i_size and unlock 4 ubifs inodes).

Gravité et risque d'exploitation

CVE-2021-47637 obtient un score CVSS de 5.5/10, soit une gravité moyenne. Selon le modèle EPSS, la probabilité qu'elle soit exploitée dans les 30 prochains jours est de 0.19 %, ce qui la place devant 8.3 % des CVE référencées.

Que faire ?

  • Vérifiez si Linux (versions 5.15.33, <=5.17.*, <70e9090acc32348cedc5def0cd6d5c126efc97b9, 5.18, <8b278c8dcfb565cb65eceb62a38cbf7a7c326db5, <9dddc8211430fb851ddf0b168e3a00c6f66cc185, 0, 9e0a1fff8db56eaaebb74b4a3ef65f86811c4798, <37bdf1ad592555ecda1d55b89f6e393e4c0589d1, <=5.10.*, <afd427048047e8efdedab30e8888044e2be5aa9c, 5.4.189, <=5.4.*, <4.9, <=4.19.*, 5.16.19, <c58af8564a7b08757173009030b74baf4b2b762b, <=5.16.*, <83e42a78428fc354f5e2049935b84c8d8d29b787, 5.10.110, 5.17.2, 4.9, 4.19.238, <=*, <=5.15.*) 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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