CVE-2026-46315: io_uring/waitid: clear waitid info before copying it to userspace

CVE-2026-46315: io_uring/waitid: clear waitid info before copying it to userspace

[Greg Kroah-Hartman]

From: Greg Kroah-Hartman <gregkh@kernel.org>

Description
===========

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

io_uring/waitid: clear waitid info before copying it to userspace

IORING_OP_WAITID stores its result fields in struct io_waitid::info and
later copies them to userspace siginfo. The prep path initializes the
request arguments, but it does not initialize info itself.

If the wait operation completes without reporting a child event, the common
wait code can return without writing wo_info. In that case io_waitid_finish()
still copies iw->info to userspace, exposing stale bytes from the reused
io_kiocb command storage.

Clear the result storage during prep so the io_uring path matches the
regular waitid syscall, which uses a zero-initialized struct waitid_info.

The Linux kernel CVE team has assigned CVE-2026-46315 to this issue.


Affected and fixed versions
===========================

	Issue introduced in 6.7 with commit f31ecf671ddc498f20219453395794ff2383e06b and fixed in 6.12.92 with commit 954518e5a4a5efc5033253f6e36fc7b9f98363a3
	Issue introduced in 6.7 with commit f31ecf671ddc498f20219453395794ff2383e06b and fixed in 6.18.34 with commit b737c6612c60c23b40a9f31749b99e6f61943847
	Issue introduced in 6.7 with commit f31ecf671ddc498f20219453395794ff2383e06b and fixed in 7.0.11 with commit 4d2a0de611ab60d02fc768ae0cd5918b16bd5474
	Issue introduced in 6.7 with commit f31ecf671ddc498f20219453395794ff2383e06b and fixed in 7.1-rc5 with commit 93d93f5f8da791e98159795c6ef683f45bd95d13

Please see https://www.kernel.org for a full list of currently supported
kernel versions by the kernel community.

Unaffected versions might change over time as fixes are backported to
older supported kernel versions.  The official CVE entry at
	https://cve.org/CVERecord/?id=CVE-2026-46315
will be updated if fixes are backported, please check that for the most
up to date information about this issue.


Affected files
==============

The file(s) affected by this issue are:
	io_uring/waitid.c


Mitigation
==========

The Linux kernel CVE team recommends that you update to the latest
stable kernel version for this, and many other bugfixes.  Individual
changes are never tested alone, but rather are part of a larger kernel
release.  Cherry-picking individual commits is not recommended or
supported by the Linux kernel community at all.  If however, updating to
the latest release is impossible, the individual changes to resolve this
issue can be found at these commits:
	https://git.kernel.org/stable/c/954518e5a4a5efc5033253f6e36fc7b9f98363a3
	https://git.kernel.org/stable/c/b737c6612c60c23b40a9f31749b99e6f61943847
	https://git.kernel.org/stable/c/4d2a0de611ab60d02fc768ae0cd5918b16bd5474
	https://git.kernel.org/stable/c/93d93f5f8da791e98159795c6ef683f45bd95d13