CVE-2024-50010

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

exec: don't WARN for racy path_noexec check

Both imode and noexec checks wrapped in WARNON stem from an artifact of the previous implementation. They used to legitimately check for the condition, but that got moved up in two commits: 633fb6ac3980 ("exec: move SISREG() check earlier") 0fd338b2d2cd ("exec: move pathnoexec() check earlier")

Instead of being removed said checks are WARN_ON'ed instead, which has some debug value.

However, the spurious path_noexec check is racy, resulting in unwarranted warnings should someone race with setting the noexec flag.

One can note there is more to perm-checking whether execve is allowed and none of the conditions are guaranteed to still hold after they were tested for.

Additionally this does not validate whether the code path did any perm checking to begin with -- it will pass if the inode happens to be regular.

Keep the redundant path_noexec() check even though it's mindless nonsense checking for guarantee that isn't given so drop the WARN.

Reword the commentary and do small tidy ups while here.

[brauner: keep redundant path_noexec() check]