[release-branch.go1.24] os/exec: fix incorrect expansion of ".." in LookPath on plan9
The correction in CL 685755 is incomplete for plan9, where path
search is performed even on file strings containing "/". By
applying filepath.Clean to the argument of validateLookPath,
we can check for bogus file strings containing ".." where the
later call to filepath.Join would transform a path like
"badfile/dir/.." to "badfile" even where "dir" isn't a directory
or doesn't exist.
For #74466
Fixes #75007
Change-Id: I3f8b73a1de6bc7d8001b1ca8e74b78722408548e
Reviewed-on: https://go-review.googlesource.com/c/go/+/693935
Reviewed-by: David du Colombier <0intro@gmail.com>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Reviewed-by: David Chase <drchase@google.com>
Reviewed-by: Dmitri Shuralyov <dmitshur@google.com>
(cherry picked from commit
674c5f0edd82b5d1dd5cb44eb4b85830245c151e)
Reviewed-on: https://go-review.googlesource.com/c/go/+/698655
TryBot-Bypass: Cherry Mui <cherryyz@google.com>
Reviewed-by: Cherry Mui <cherryyz@google.com>