Re: [PATCH] fchmodat, lchmod: port to buggy Linux filesystems

2020-03-11 Thread Paul Eggert
On 3/11/20 2:04 AM, Kamil Dudka wrote: Would not it make sense to fix this in mknod by turning the EOPNOTSUPP failure into a warning only? No, because that would be a regression. mknod used to work in this case, and now it doesn't. Formerly, Gnulib-using programs like mknod worked around

Re: [PATCH] fchmodat, lchmod: port to buggy Linux filesystems

2020-03-11 Thread Paul Eggert
On 3/11/20 1:45 AM, Florian Weimer wrote: I now wonder if neither gnulib nor glibc should pretend that they can implement lchmod and fchmodat on Linux in a usable fashion. That ship sailed long ago for Gnulib, since it long emulated lchmod by using chmod (with no symlink check!), and

Re: [PATCH] fchmodat, lchmod: port to buggy Linux filesystems

2020-03-11 Thread Kamil Dudka
On Tuesday, March 10, 2020 8:30:36 PM CET Florian Weimer wrote: > * Pádraig Brady: > > On 10/03/2020 11:52, Florian Weimer wrote: > >> * Pádraig Brady: > >>> On 09/03/2020 18:51, Paul Eggert wrote: > On 3/9/20 10:30 AM, Pádraig Brady wrote: > > A very similar "ENOTSUP" problem is being

Re: [PATCH] fchmodat, lchmod: port to buggy Linux filesystems

2020-03-11 Thread Florian Weimer
* Paul Eggert: > On 3/10/20 12:30 PM, Florian Weimer wrote: >> The glibc implementation needs /proc to avoid the race. There is no >> way around that, otherwise we introduce a security vulnerability. > > It is unfortunate that we have dueling paranoia here. coreutils mknod is > paranoid so it

Re: [PATCH] fchmodat, lchmod: port to buggy Linux filesystems

2020-03-11 Thread Florian Weimer
* Paul Eggert: > On 3/10/20 12:30 PM, Florian Weimer wrote: > >> Is the concern here that >> you would get a different mode from the requested one if you use >> umask+mknod and not mknod+some form of chmod? > > Yes. See: > > https://bugs.gnu.org/14371 Wrong bug? There is no --mode argument

Re: [PATCH] fchmodat, lchmod: port to buggy Linux filesystems

2020-03-11 Thread Paul Eggert
On 3/10/20 12:30 PM, Florian Weimer wrote: Is the concern here that you would get a different mode from the requested one if you use umask+mknod and not mknod+some form of chmod? Yes. See: https://bugs.gnu.org/14371

Re: [PATCH] fchmodat, lchmod: port to buggy Linux filesystems

2020-03-11 Thread Paul Eggert
On 3/10/20 12:30 PM, Florian Weimer wrote: The glibc implementation needs /proc to avoid the race. There is no way around that, otherwise we introduce a security vulnerability. It is unfortunate that we have dueling paranoia here. coreutils mknod is paranoid so it uses lchmod to avoid a