On Tue, Jul 11, 2023 at 06:16:04PM +0200, Alexey Gladkov wrote: > On the userspace side fchmodat(3) is implemented as a wrapper > function which implements the POSIX-specified interface. This > interface differs from the underlying kernel system call, which does not > have a flags argument. Most implementations require procfs [1][2]. > > There doesn't appear to be a good userspace workaround for this issue > but the implementation in the kernel is pretty straight-forward. > > The new fchmodat2() syscall allows to pass the AT_SYMLINK_NOFOLLOW flag, > unlike existing fchmodat. > > [1] https://sourceware.org/git/?p=glibc.git;a=blob;f=sysdeps/unix/sysv/linux/fchmodat.c;h=17eca54051ee28ba1ec3f9aed170a62630959143;hb=a492b1e5ef7ab50c6fdd4e4e9879ea5569ab0a6c#l35 > [2] https://git.musl-libc.org/cgit/musl/tree/src/stat/fchmodat.c?id=718f363bc2067b6487900eddc9180c84e7739f80#n28 > > Co-developed-by: Palmer Dabbelt <palmer@xxxxxxxxxx> > Signed-off-by: Palmer Dabbelt <palmer@xxxxxxxxxx> > Signed-off-by: Alexey Gladkov <legion@xxxxxxxxxx> > Acked-by: Arnd Bergmann <arnd@xxxxxxxx> > --- > fs/open.c | 18 ++++++++++++++---- > include/linux/syscalls.h | 2 ++ > 2 files changed, 16 insertions(+), 4 deletions(-) > > diff --git a/fs/open.c b/fs/open.c > index 0c55c8e7f837..39a7939f0d00 100644 > --- a/fs/open.c > +++ b/fs/open.c > @@ -671,11 +671,11 @@ SYSCALL_DEFINE2(fchmod, unsigned int, fd, umode_t, mode) > return err; > } > > -static int do_fchmodat(int dfd, const char __user *filename, umode_t mode) > +static int do_fchmodat(int dfd, const char __user *filename, umode_t mode, int lookup_flags) Should all be unsigned instead of int here for flags. We also had a documentation update to that effect but smh never sent it. user_path_at() itself takes an unsigned as well. I'll fix that up though.
