tree 7b9bfe412a92bc05c61e3b36db97ea571347c3ed
parent d233388d81b4e91fb281273d5c949800e5717e7c
author Peter Zijlstra <peterz@infradead.org> 1697630214 +0200
committer Oleksandr Tymoshenko <ovt@google.com> 1698783262 +0000

perf: Disallow mis-matched inherited group reads

commit 32671e3799ca2e4590773fd0e63aaa4229e50c06 upstream.

Because group consistency is non-atomic between parent (filedesc) and children
(inherited) events, it is possible for PERF_FORMAT_GROUP read() to try and sum
non-matching counter groups -- with non-sensical results.

Add group_generation to distinguish the case where a parent group removes and
adds an event and thus has the same number, but a different configuration of
events as inherited groups.

This became a problem when commit fa8c269353d5 ("perf/core: Invert
perf_read_group() loops") flipped the order of child_list and sibling_list.
Previously it would iterate the group (sibling_list) first, and for each
sibling traverse the child_list. In this order, only the group composition of
the parent is relevant. By flipping the order the group composition of the
child (inherited) events becomes an issue and the mis-match in group
composition becomes evident.

That said; even prior to this commit, while reading of a group that is not
equally inherited was not broken, it still made no sense.

(Ab)use ECHILD as error return to indicate issues with child process group
composition.

BUG=b/308500870
TEST=presubmit
RELEASE_NOTE=Fixed CVE-2023-5717 in the Linux kernel.

cos-patch: security-high
Fixes: fa8c269353d5 ("perf/core: Invert perf_read_group() loops")
Reported-by: Budimir Markovic <markovicbudimir@gmail.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lkml.kernel.org/r/20231018115654.GK33217@noisy.programming.kicks-ass.net
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Change-Id: I250e688f5ff3af3c5c7e0d52779fa7dc74d3c68b
Reviewed-on: https://cos-review.googlesource.com/c/third_party/kernel/+/60238
Tested-by: Cusky Presubmit Bot <presubmit@cos-infra-prod.iam.gserviceaccount.com>
Reviewed-by: Arnav Kansal <rnv@google.com>