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CVE-2026-74363

bpf: fix UAF by restoring RCU-delayed inode freeing in bpffs

Published
Last modified
published
Not listed in CISA KEV
Fix
Fixed in 5.15.212, 6.1.178, 6.6.145, 6.12.97, 6.18, and 2 more
None on Exploit-DB, Metasploit or GitHub
  • Exploitation: none
  • Automatable: no
  • Technical impact: total

Summary

In the Linux kernel, the following vulnerability has been resolved: bpf: fix UAF by restoring RCU-delayed inode freeing in bpffs commit 4f375ade6aa9 ("bpf: Avoid RCU context warning when unpinning htab with internal structs") moved inode cleanup from ->free_inode() into ->destroy_inode() to avoid sleeping in RCU context when calling bpf_any_put(). However this removed the RCU delay on freeing the inode itself and the cached symlink body (i_link), both of which can be accessed by RCU pathwalk (pick_link, may_lookup etc.). This causes a use-after-free when a concurrent unlinkat() drops the last inode reference and destroy_inode() frees the inode immediately, while another task is still walking the path in RCU mode and reads inode->i_opflags (offset +2) inside current_time() -> is_mgtime(). KASAN reports: BUG: KASAN: slab-use-after-free in is_mgtime include/linux/fs.h:2313 Read of size 2 at addr ffff8880407e4282 (offset +2 = i_opflags) The rules (per Al Viro): ->destroy_inode() called immediately, can sleep, use for blocking cleanup e.g. bpf_any_put() ->free_inode() called after RCU grace period, use for freeing inode and anything RCU-accessible e.g. i_link Fix: split the two concerns properly: • keep bpf_any_put() in bpf_destroy_inode() since it is blocking and needs to run promptly • introduce bpf_free_inode() to handle kfree(i_link) and free_inode_nonrcu() with proper RCU delay, preventing the UAF

Timeline

  1. CVE published
  2. CISA SSVC assessment

    Exploitation: none · Automatable: no · Technical impact: total

  3. Record last updated

Affected versions

  • Linux Linux

    From e28616ca3d67e745ecb2f10eba4a626e1fc9a203 · fixed in ea1c243c39e32b7fc1c2edfe32081ff7e30a877c; From 743a620c661994c7f0938e6dd32fb0883fb1e0ea · fixed in 5fecb71c10c28aef276ba49c718dc961745fdcf0; From b6e9645be9eb93f7aff3ca887f8edb6f1d63358f · fixed in c70d0f9114c3cc156f6029a400c4eb7e6f7c82b2; From ee04cff9ed4d6bb25802f5cecfcd0750500410f3 · fixed in 53649846e0437d1d9b7cb993cfe54c367addf7ae; From 4f375ade6aa9f37fd72d7a78682f639772089eed · fixed in 61f19729728243c82476dee31315143ed3275e7f; From 4f375ade6aa9f37fd72d7a78682f639772089eed · fixed in 0497ff765746d9b2d17445c8f7cc737b36c0152a; From 4f375ade6aa9f37fd72d7a78682f639772089eed · fixed in b93c55b4932dd7e32dca8cf34a3443cc87a02906; From 5.15.195 · fixed in 5.15.212; From 6.1.157 · fixed in 6.1.178; From 6.6.113 · fixed in 6.6.145; From 6.12.54 · fixed in 6.12.97; From 6.17.4 · fixed in 6.18

  • Linux Linux

    6.18

  • KernelLinux

    fixed in 5.15.212; From 5.16.0 · fixed in 6.1.178; From 6.2.0 · fixed in 6.6.145; From 6.7.0 · fixed in 6.12.97; From 6.13.0 · fixed in 6.18.40; From 6.18.0 · fixed in 7.1.5

References 7

git.kernel.org