In the Linux kernel, the following vulnerability has been resolved: io_uring/poll: correctly handle io_poll_add() return value on update When the core of io_uring was updated to handle completions consistently and with fixed return codes, the POLL_REMOVE opcode with updates got slightly broken. If a POLL_ADD is pending and then POLL_REMOVE is used to update the events of that request, if that update causes the POLL_ADD to now trigger, then that completion is lost and a CQE is never posted. Additionally, ensure that if an update does cause an existing POLL_ADD to complete, that the completion value isn't always overwritten with -ECANCELED. For that case, whatever io_poll_add() set the value to should just be retained.
https://git.kernel.org/stable/c/c1669c03bfbc2a9b5ebff4428eecebe734c646fe
https://git.kernel.org/stable/c/8b777ab48441b153502772ecfc78c107d4353f29
https://git.kernel.org/stable/c/84230ad2d2afbf0c44c32967e525c0ad92e26b4e
https://git.kernel.org/stable/c/13a8f7b88c2d40c6b33f6216190478dda95d385f
https://git.kernel.org/stable/c/0126560370ed5217958b85657b590ad25e8b9c00