CVE-2026-31484

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

iouring/fdinfo: fix OOB read in SQEMIXED wrap check

__iouringshowfdinfo() iterates over pending SQEs and, for 128-byte SQEs on an IORINGSETUPSQEMIXED ring, needs to detect when the second half of the SQE would be past the end of the sqsqes array. The current check tests (++sqhead & sqmask) == 0, but sqhead is only incremented when a 128-byte SQE is encountered, not on every iteration. The actual array index is sqidx = (i + sqhead) & sqmask, which can be sqmask (the last slot) while the wrap check passes.

Fix by checking sqidx directly. Keep the sqhead increment so the loop still skips the second half of the 128-byte SQE on the next iteration.