io_uring/cmd: don't leave list poison in ->hash_node

Overview

In the Linux kernel, the following vulnerability has been resolved:

io_uring/cmd: don't leave list poison in ->hash_node

io_uring_cmd_del_cancelable() uses hlist_del() to take a command off ->cancelable_uring_cmd, which leaves LIST_POISON1/2 behind in ->hash_node. Requests are recycled through the request cache without being reinitialised, and not every user of ->hash_node sets it up before it is used:

If a vectored futex wait is woken while futex_wait_multiple_setup() is still queueing the futexes, io_futexv_wait() doesn't add the request to ->futex_list, and leaves the completion to the task_work queued by the wake up. io_futexv_complete() ends in __io_futex_complete(), whose hlist_del_init() is fine for a request that is unhashed, which is how all other users of the node leave it. If the request was a cancelable uring_cmd in its previous life, e.g. a ublk FETCH_REQ, it writes through LIST_POISON2:

Oops: general protection fault, probably for non-canonical address KASAN: maybe wild-memory-access in range [0xdead000000000120-...] RIP: 0010:io_futexv_complete+0x219/0x420 Call Trace: tctx_task_work_run+0x804/0x950 tctx_task_work+0x71/0xa0 task_work_run+0x118/0x200

Leave the node unhashed.

Affected

• Linux >= 93b8cc60c37b9d17732b7a297e5dca29b50a990d < cc7f13d006fcefed9564bd79f135b51d344e9c77
• Linux >= 93b8cc60c37b9d17732b7a297e5dca29b50a990d < 2d5af21422060c088f6e4fb0f1e7dcf5bcdd6707
• Linux >= 93b8cc60c37b9d17732b7a297e5dca29b50a990d < 685b49483200384d7f49d338af476e26e6824637
• Linux >= 93b8cc60c37b9d17732b7a297e5dca29b50a990d < c4fe1024b2f3f40f8010591a0c0ad541e2883eda
• Linux >= 93b8cc60c37b9d17732b7a297e5dca29b50a990d < 4c83e39f4d1944d7146fd06094f2c8053238d55c
• Linux 6.7

Remediation

Refer to the linked advisories for vendor-supplied fixes and affected version ranges.