[looks like linux-abi is a typo, Cc'ed linux-api instead] On Thu, May 16, 2019 at 05:50:22PM +0100, Al Viro wrote: > [linux-abi cc'd] > > On Thu, May 16, 2019 at 06:31:52PM +0200, Christian Brauner wrote: > > On Thu, May 16, 2019 at 05:22:59PM +0100, Al Viro wrote: > > > On Thu, May 16, 2019 at 12:52:04PM +0100, David Howells wrote: > > > > > > > > Hi Linus, Al, > > > > > > > > Here are some patches that make changes to the mount API UAPI and two of > > > > them really need applying, before -rc1 - if they're going to be applied at > > > > all. > > > > > > I'm fine with 2--4, but I'm not convinced that cloexec-by-default crusade > > > makes any sense. Could somebody give coherent arguments in favour of > > > abandoning the existing conventions? > > > > So as I said in the commit message. From a userspace perspective it's > > more of an issue if one accidently leaks an fd to a task during exec. > > > > Also, most of the time one does not want to inherit an fd during an > > exec. It is a hazzle to always have to specify an extra flag. > > > > As Al pointed out to me open() semantics are not going anywhere. Sure, > > no argument there at all. > > But the idea of making fds cloexec by default is only targeted at fds > > that come from separate syscalls. fsopen(), open_tree_clone(), etc. they > > all return fds independent of open() so it's really easy to have them > > cloexec by default without regressing anyone and we also remove the need > > for a bunch of separate flags for each syscall to turn them into > > cloexec-fds. I mean, those for syscalls came with 4 separate flags to be > > able to specify that the returned fd should be made cloexec. The other > > way around, cloexec by default, fcntl() to remove the cloexec bit is way > > saner imho. > > Re separate flags - it is, in principle, a valid argument. OTOH, I'm not > sure if they need to be separate - they all have the same value and > I don't see any reason for that to change... > > Only tangentially related, but I wonder if something like close_range(from, to) > would be a more useful approach... That kind of open-coded loops is not > rare in userland and kernel-side code can do them much cheaper. Something > like > /* that exec is sensitive */ > unshare(CLONE_FILES); > /* we don't want anything past stderr here */ > close_range(3, ~0U); > execve(....); > on the userland side of thing. Comments? glibc people need a syscall to implement closefrom properly, see https://sourceware.org/bugzilla/show_bug.cgi?id=10353#c14 -- ldv
