CVE-2026-31484io_uring/fdinfo: fix OOB read in SQE_MIXED wrap check

Official description

In the Linux kernel, the following vulnerability has been resolved: io_uring/fdinfo: fix OOB read in SQE_MIXED wrap check __io_uring_show_fdinfo() iterates over pending SQEs and, for 128-byte SQEs on an IORING_SETUP_SQE_MIXED ring, needs to detect when the second half of the SQE would be past the end of the sq_sqes array. The current check tests (++sq_head & sq_mask) == 0, but sq_head is only incremented when a 128-byte SQE is encountered, not on every iteration. The actual array index is sq_idx = (i + sq_head) & sq_mask, which can be sq_mask (the last slot) while the wrap check passes. Fix by checking sq_idx directly. Keep the sq_head increment so the loop still skips the second half of the 128-byte SQE on the next iteration.

Affected packages & fixed versions

Affected products (as reported)

References

• https://git.kernel.org/stable/c/ba21ab247a5be5382da7464b95afbe5f0e9aa503
• https://git.kernel.org/stable/c/5170efd9c344c68a8075dcb8ed38d3f8a60e7ed4