Description

In the Linux kernel, the following vulnerability has been resolved: io_uring/poll: fix signed comparison in io_poll_get_ownership() io_poll_get_ownership() uses a signed comparison to check whether poll_refs has reached the threshold for the slowpath: if (unlikely(atomic_read(&req->poll_refs) >= IO_POLL_REF_BIAS)) atomic_read() returns int (signed). When IO_POLL_CANCEL_FLAG (BIT(31)) is set in poll_refs, the value becomes negative in signed arithmetic, so the >= 128 comparison always evaluates to false and the slowpath is never taken. Fix this by casting the atomic_read() result to unsigned int before the comparison, so that the cancel flag is treated as a large positive value and correctly triggers the slowpath.

References 6

• git.kernel.org https://git.kernel.org/stable/c/326941b22806cbf2df1fbfe902b7908b368cce42
• git.kernel.org https://git.kernel.org/stable/c/81bf96b0abbfa4cd47ea32e12596aed3855fb2f3
• git.kernel.org https://git.kernel.org/stable/c/c6d191164dc81838d8dbf452a6000f68c558d1ae
• git.kernel.org https://git.kernel.org/stable/c/cf522703d4f194991615763697ae25a3f9539763
• git.kernel.org https://git.kernel.org/stable/c/ea0697129807d718037f618221037aa0660ee3c5
• git.kernel.org https://git.kernel.org/stable/c/fc47043f3d9af3efa407665b47f8378ec691ba18

Remediation