On 2021-10-12 at 00:48 +0700, Robert Elz wrote: > | When execve returns this error for what is a clearly invalid > reason, > > The problem is that sometimes it will probably be an invalid reason > (that's where the race conditions can matter, that the file was there > when it was checked doesn't mean it is still there now, so the reason > might be valid, and I'm not sure it is really worth another stat() to > find out - and even if the stat() is done and that says the file > exists,
Note I did NOT add a stat() call. It was already there in bash, *after* execve() fails (so it can do a manual script run, etc.). I only changed the error message it outputs in this case. > the exec attempt might just have happened in the middle of a > mv a a.old; mv a.new a > sequence). Sure, that could happen.¹ Still, I think the error message saying that execve() failed but the program exists is not that misguided. And, more importantly, fixes the general issue of the misleading "No such file or directory" for files requesting an ELF interpreter which is not available in the current system. If this race condition was such a big deal, then we should also be concerned about a program being replaced with a directory. Or a shell script with a binary file once it decides it can be executed as a script. If someone changes the binary between execve() time and when bash examines it (as it already does), the diagnostic can be wrong. But that's still no worse than the alternative of letting the user inspect it manually. Best regards ¹ And the obvious solution if it is expected a can be run at any point would have been to instead do: ln a a.old; mv a.new a
