CVE-2024-50010

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

exec: don't WARN for racy path_noexec check

Both i_mode and noexec checks wrapped in WARN_ON 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 S_ISREG() check earlier")

0fd338b2d2cd ("exec: move path_noexec() 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]