| Message ID | 20190531191204.4044-3-palmer@sifive.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | [1/5] Non-functional cleanup of a "__user * filename" | expand |
On Fri, May 31, 2019 at 9:23 PM Palmer Dabbelt <palmer@sifive.com> wrote: > > man 3p says that fchmodat() takes a flags argument, but the Linux > syscall does not. There doesn't appear to be a good userspace > workaround for this issue but the implementation in the kernel is pretty > straight-forward. The specific use case where the missing flags came up > was WRT a fuse filesystem implemenation, but the functionality is pretty > generic so I'm assuming there would be other use cases. > > Signed-off-by: Palmer Dabbelt <palmer@sifive.com> > --- > fs/open.c | 21 +++++++++++++++++++-- > include/linux/syscalls.h | 5 +++++ > 2 files changed, 24 insertions(+), 2 deletions(-) > > diff --git a/fs/open.c b/fs/open.c > index a00350018a47..cfad7684e8d3 100644 > --- a/fs/open.c > +++ b/fs/open.c > @@ -568,11 +568,17 @@ SYSCALL_DEFINE2(fchmod, unsigned int, fd, umode_t, mode) > return ksys_fchmod(fd, mode); > } > > -int do_fchmodat(int dfd, const char __user *filename, umode_t mode) > +int do_fchmodat4(int dfd, const char __user *filename, umode_t mode, int flags) ... > + > +int do_fchmodat(int dfd, const char __user *filename, umode_t mode) > +{ > + return do_fchmodat4(dfd, filename, mode, 0); > +} > + There is only one external caller of do_fchmodat(), so just change that to pass the extra argument here, and keep a single do_fchmodat() function used by the sys_fchmod(), sys_fchmod4(), sys_chmod() and ksys_chmod(). Arnd
On Fri, 31 May 2019 12:51:00 PDT (-0700), Arnd Bergmann wrote: > On Fri, May 31, 2019 at 9:23 PM Palmer Dabbelt <palmer@sifive.com> wrote: >> >> man 3p says that fchmodat() takes a flags argument, but the Linux >> syscall does not. There doesn't appear to be a good userspace >> workaround for this issue but the implementation in the kernel is pretty >> straight-forward. The specific use case where the missing flags came up >> was WRT a fuse filesystem implemenation, but the functionality is pretty >> generic so I'm assuming there would be other use cases. >> >> Signed-off-by: Palmer Dabbelt <palmer@sifive.com> >> --- >> fs/open.c | 21 +++++++++++++++++++-- >> include/linux/syscalls.h | 5 +++++ >> 2 files changed, 24 insertions(+), 2 deletions(-) >> >> diff --git a/fs/open.c b/fs/open.c >> index a00350018a47..cfad7684e8d3 100644 >> --- a/fs/open.c >> +++ b/fs/open.c >> @@ -568,11 +568,17 @@ SYSCALL_DEFINE2(fchmod, unsigned int, fd, umode_t, mode) >> return ksys_fchmod(fd, mode); >> } >> >> -int do_fchmodat(int dfd, const char __user *filename, umode_t mode) >> +int do_fchmodat4(int dfd, const char __user *filename, umode_t mode, int flags) > ... >> + >> +int do_fchmodat(int dfd, const char __user *filename, umode_t mode) >> +{ >> + return do_fchmodat4(dfd, filename, mode, 0); >> +} >> + > > There is only one external caller of do_fchmodat(), so just change that > to pass the extra argument here, and keep a single do_fchmodat() > function used by the sys_fchmod(), sys_fchmod4(), sys_chmod() > and ksys_chmod(). OK, I'll roll that up into a v2.
diff --git a/fs/open.c b/fs/open.c index a00350018a47..cfad7684e8d3 100644 --- a/fs/open.c +++ b/fs/open.c @@ -568,11 +568,17 @@ SYSCALL_DEFINE2(fchmod, unsigned int, fd, umode_t, mode) return ksys_fchmod(fd, mode); } -int do_fchmodat(int dfd, const char __user *filename, umode_t mode) +int do_fchmodat4(int dfd, const char __user *filename, umode_t mode, int flags) { struct path path; int error; - unsigned int lookup_flags = LOOKUP_FOLLOW; + unsigned int lookup_flags; + + if (unlikely(flags & ~AT_SYMLINK_NOFOLLOW)) + return -EINVAL; + + lookup_flags = flags & AT_SYMLINK_NOFOLLOW ? 0 : LOOKUP_FOLLOW; + retry: error = user_path_at(dfd, filename, lookup_flags, &path); if (!error) { @@ -586,6 +592,17 @@ int do_fchmodat(int dfd, const char __user *filename, umode_t mode) return error; } +SYSCALL_DEFINE4(fchmodat4, int, dfd, const char __user *, filename, + umode_t, mode, int, flags) +{ + return do_fchmodat4(dfd, filename, mode, flags); +} + +int do_fchmodat(int dfd, const char __user *filename, umode_t mode) +{ + return do_fchmodat4(dfd, filename, mode, 0); +} + SYSCALL_DEFINE3(fchmodat, int, dfd, const char __user *, filename, umode_t, mode) { diff --git a/include/linux/syscalls.h b/include/linux/syscalls.h index 396871b218f4..cb040a412a4c 100644 --- a/include/linux/syscalls.h +++ b/include/linux/syscalls.h @@ -435,6 +435,8 @@ asmlinkage long sys_chroot(const char __user *filename); asmlinkage long sys_fchmod(unsigned int fd, umode_t mode); asmlinkage long sys_fchmodat(int dfd, const char __user *filename, umode_t mode); +asmlinkage long sys_fchmodat4(int dfd, const char __user *filename, + umode_t mode, int flags); asmlinkage long sys_fchownat(int dfd, const char __user *filename, uid_t user, gid_t group, int flag); asmlinkage long sys_fchown(unsigned int fd, uid_t user, gid_t group); @@ -1315,6 +1317,9 @@ static inline long ksys_link(const char __user *oldname, extern int do_fchmodat(int dfd, const char __user *filename, umode_t mode); +extern int do_fchmodat4(int dfd, const char __user *filename, umode_t mode, + int flags); + static inline int ksys_chmod(const char __user *filename, umode_t mode) { return do_fchmodat(AT_FDCWD, filename, mode);
man 3p says that fchmodat() takes a flags argument, but the Linux syscall does not. There doesn't appear to be a good userspace workaround for this issue but the implementation in the kernel is pretty straight-forward. The specific use case where the missing flags came up was WRT a fuse filesystem implemenation, but the functionality is pretty generic so I'm assuming there would be other use cases. Signed-off-by: Palmer Dabbelt <palmer@sifive.com> --- fs/open.c | 21 +++++++++++++++++++-- include/linux/syscalls.h | 5 +++++ 2 files changed, 24 insertions(+), 2 deletions(-)