loop: Fix use-after-free issues

Summary

In the Linux kernel, the following vulnerability has been resolved: loop: Fix use-after-free issues do_req_filebacked() calls blk_mq_complete_request() synchronously or asynchronously when using asynchronous I/O unless memory allocation fails. Hence, modify loop_handle_cmd() such that it does not dereference 'cmd' nor 'rq' after do_req_filebacked() finished unless we are sure that the request has not yet been completed. This patch fixes the following kernel crash: Unable to handle kernel NULL pointer dereference at virtual address 0000000000000054 Call trace: css_put.42938+0x1c/0x1ac loop_process_work+0xc8c/0xfd4 loop_rootcg_workfn+0x24/0x34 process_one_work+0x244/0x558 worker_thread+0x400/0x8fc kthread+0x16c/0x1e0 ret_from_fork+0x10/0x20

Timeline

1. May 2, 2025, 3:55 PM UTCCVE published
2. Oct 15, 2026, 9:33 PM UTCCISA SSVC assessment

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

3. Oct 15, 2026, 9:41 PM UTCRecord last updated

Affected versions

• Linux Linux

  From bc07c10a3603a5ab3ef01ba42b3d41f9ac63d1b6 · fixed in 407badf73ec9fb0d5744bf2ca1745c1818aa222f; From bc07c10a3603a5ab3ef01ba42b3d41f9ac63d1b6 · fixed in e3fda704903f6d1fc351412f1bc6620333959ada; From bc07c10a3603a5ab3ef01ba42b3d41f9ac63d1b6 · fixed in 6917395c4667cfb607ed8bf1826205a59414657c; From bc07c10a3603a5ab3ef01ba42b3d41f9ac63d1b6 · fixed in 9b0cb770f5d7b1ff40bea7ca385438ee94570eec

• Linux Linux

  4.4

• KernelLinux

  From 4.4.0 · fixed in 5.15.104; From 5.16.0 · fixed in 6.1.21; From 6.2.0 · fixed in 6.2.8

References 4