CVE-2025-21633 Information

Description

In the Linux kernel the following vulnerability has been resolved:

io_uring/sqpoll: zero sqd->thread on tctx errors

Syzkeller reports:

BUG: KASAN: slab-use-after-free in thread_group_cputime+0x409/0x700 kernel/sched/cputime.c:341 Read of size 8 at addr ffff88803578c510 by task syz.2.3223/27552 Call Trace: … kasan_report+0x143/0x180 mm/kasan/report.c:602 thread_group_cputime+0x409/0x700 kernel/sched/cputime.c:341 thread_group_cputime_adjusted+0xa6/0x340 kernel/sched/cputime.c:639 getrusage+0x1000/0x1340 kernel/sys.c:1863 io_uring_show_fdinfo+0xdfe/0x1770 io_uring/fdinfo.c:197 seq_show+0x608/0x770 fs/proc/fd.c:68 …

That’s due to sqd->task not being cleared properly in cases where SQPOLL task tctx setup fails which can essentially only happen with fault injection to insert allocation errors.

Reference

https://git.kernel.org/stable/c/4b7cfa8b6c28a9fa22b86894166a1a34f6d630ba https://git.kernel.org/stable/c/aa7496d668c30ca7421b3bfdcd948ee861a13d17