CVE-2026-99228: io_uring/io-wq: don't lose the signal that ends work

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

iouring/io-wq: don't lose the signal that ends work

When a thread exits, only its tracked requests are cancelled. Then its io-wq is torn down. iowqexitworkers() signals every worker, to get it out of an interruptible sleep, and waits for all of them to exit. Before they do, they go through the work that is left. Unbounded work is cancelled. Bounded work is run, as it is expected to end by itself.

Not all of it does. An open has no file yet, so it counts as bounded, and the open of a FIFO waits for the other end. That is what the signal is for. But the workers are signalled once, and a worker that hasn't started the work by then loses the signal:

iowqexitworkers() ioworkerhandlework() iowqworkerwake() set TIFNOTIFYSIGNAL ioassigncurrentwork() ioruntaskwork() clear TIFNOTIFYSIGNAL iowqsubmitwork() fifoopen() waitforpartner() waitforcompletiontimeout()

The thread never gets out of doexit():

IORINGOPOPENAT of a FIFO without a writer, IOSQEASYNC exit of the thread that has submitted it

hangs in more than 9 of 10 attempts (4 CPUs, KVM), until the process is killed.

Set TIFNOTIFYSIGNAL for bounded work that is started with IOWQBITEXIT set. The bit is set before the workers are signalled, and it is tested after the flag has been cleared, with clearnotifysignal() providing the barrier. So either the flag stays, or the bit is seen.

Work that is started while the io-wq exits is treated like work that is being run at that time: it isn't interrupted unless it waits interruptibly.