Re: [PATCH 2/2] vfs: Make sure {statx,fstatat}(..., AT_EMPTY_PATH | ..., NULL, ...) behave as (..., AT_EMPTY_PATH | ..., "", ...)

[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

 



On Mon, Oct 7, 2024 at 3:08 PM Xi Ruoyao <xry111@xxxxxxxxxxx> wrote:
>
> We've supported {statx,fstatat}(real_fd, NULL, AT_EMPTY_PATH, ...) since
> Linux 6.11 for better performance.  However there are other cases, for
> example using AT_FDCWD as the fd or having AT_SYMLINK_NOFOLLOW in flags,
> not covered by the fast path.  While it may be impossible, too
> difficult, or not very beneficial to optimize these cases, we should
> still turn NULL into "" for them in the slow path to make the API easier
> to be documented and used.
>
> Fixes: 0ef625bba6fb ("vfs: support statx(..., NULL, AT_EMPTY_PATH, ...)")
> Cc: stable@xxxxxxxxxxxxxxx
> Signed-off-by: Xi Ruoyao <xry111@xxxxxxxxxxx>
> ---
>  fs/stat.c | 10 ++++++++--
>  1 file changed, 8 insertions(+), 2 deletions(-)
>
> diff --git a/fs/stat.c b/fs/stat.c
> index ed9d4fd8ba2c..5d1b51c23c62 100644
> --- a/fs/stat.c
> +++ b/fs/stat.c
> @@ -337,8 +337,11 @@ int vfs_fstatat(int dfd, const char __user *filename,
>         flags &= ~AT_NO_AUTOMOUNT;
>         if (flags == AT_EMPTY_PATH && vfs_empty_path(dfd, filename))
>                 return vfs_fstat(dfd, stat);
> +       else if ((flags & AT_EMPTY_PATH) && !filename)
> +               name = getname_kernel("");
> +       else
> +               name = getname_flags(filename, getname_statx_lookup_flags(statx_flags));
>
> -       name = getname_flags(filename, getname_statx_lookup_flags(statx_flags));
>         ret = vfs_statx(dfd, name, statx_flags, stat, STATX_BASIC_STATS);
>         putname(name);
>
> @@ -791,8 +794,11 @@ SYSCALL_DEFINE5(statx,
>         lflags = flags & ~(AT_NO_AUTOMOUNT | AT_STATX_SYNC_TYPE);
>         if (lflags == AT_EMPTY_PATH && vfs_empty_path(dfd, filename))
>                 return do_statx_fd(dfd, flags & ~AT_NO_AUTOMOUNT, mask, buffer);
> +       else if ((lflags & AT_EMPTY_PATH) && !filename)
> +               name = getname_kernel("");
> +       else
> +               name = getname_flags(filename, getname_statx_lookup_flags(flags));
>
> -       name = getname_flags(filename, getname_statx_lookup_flags(flags));
>         ret = do_statx(dfd, name, flags, mask, buffer);
>         putname(name);
>

I thought you are going to patch up the 2 callsites of
vfs_empty_path() or add the flags argument to said routine so that it
can do the branching internally.

Either way I don't think implementing AT_FDCWD + NULL + AT_EMPTY_PATH
with  getname_kernel("") is necessary.

-- 
Mateusz Guzik <mjguzik gmail.com>





[Index of Archives]     [Linux Ext4 Filesystem]     [Union Filesystem]     [Filesystem Testing]     [Ceph Users]     [Ecryptfs]     [NTFS 3]     [AutoFS]     [Kernel Newbies]     [Share Photos]     [Security]     [Netfilter]     [Bugtraq]     [Yosemite News]     [MIPS Linux]     [ARM Linux]     [Linux Security]     [Linux Cachefs]     [Reiser Filesystem]     [Linux RAID]     [NTFS 3]     [Samba]     [Device Mapper]     [CEPH Development]

  Powered by Linux