Re: [PATCH 1/1] 9p-local.c: always return -1 on error in local_unlinkat_common

[Daniel Henrique Barboza]

On 1/7/20 1:47 PM, Greg Kurz wrote:
> I've changed "9p-local.c:" to "9p: local:" which is the usual prefix used for
> fsdev backend specific changes.

Good to know. Thanks for fixing it up.

> On Tue,  7 Jan 2020 11:47:18 -0300
> Daniel Henrique Barboza <address@hidden> wrote:
>
> > local_unlinkat_common() is supposed to always return -1 on error.
> > This is being done by jumps to the 'err_out' label, which is
> > a 'return ret' call, and 'ret' is initialized with -1.
> >
> > Unfortunately there is a condition in which the function will
> > return 0 on error: in a case where flags == AT_REMOVEDIR, 'ret'
> > will be 0 when reaching
> >
> > map_dirfd = openat_dir(...)
> >
> > And, if map_dirfd == -1 and errno != ENOENT, the existing 'err_out'
> > jump will execute 'return ret', when ret is still set to zero
> > at that point.
> >
> > This patch fixes it by changing all 'err_out' labels by
> > 'return -1' calls, ensuring that the function will always
> > return -1 on error conditions. 'ret' can be left unintialized
> > since it's now being used just to store the result of 'unlinkat'
> > calls.
> >
> > CC: Greg Kurz <address@hidden>
> > Signed-off-by: Daniel Henrique Barboza <address@hidden>
> > ---
>
> Applied to 9p-next.
>
> Thanks Daniel and feliz ano novo :)


Bonne année!




> >   hw/9pfs/9p-local.c | 14 ++++++--------
> >   1 file changed, 6 insertions(+), 8 deletions(-)
> >
> > diff --git a/hw/9pfs/9p-local.c b/hw/9pfs/9p-local.c
> > index ca641390fb..de61aca216 100644
> > --- a/hw/9pfs/9p-local.c
> > +++ b/hw/9pfs/9p-local.c
> > @@ -1076,7 +1076,7 @@ out:
> >   static int local_unlinkat_common(FsContext *ctx, int dirfd, const char *name,
> >                                    int flags)
> >   {
> > -    int ret = -1;
> > +    int ret;
> >   
> >       if (ctx->export_flags & V9FS_SM_MAPPED_FILE) {
> >           int map_dirfd;
> > @@ -1094,12 +1094,12 @@ static int local_unlinkat_common(FsContext *ctx, int 
> > dirfd, const char *name,
> >   
> >               fd = openat_dir(dirfd, name);
> >               if (fd == -1) {
> > -                goto err_out;
> > +                return -1;
> >               }
> >               ret = unlinkat(fd, VIRTFS_META_DIR, AT_REMOVEDIR);
> >               close_preserve_errno(fd);
> >               if (ret < 0 && errno != ENOENT) {
> > -                goto err_out;
> > +                return -1;
> >               }
> >           }
> >           map_dirfd = openat_dir(dirfd, VIRTFS_META_DIR);
> > @@ -1107,16 +1107,14 @@ static int local_unlinkat_common(FsContext *ctx, int 
> > dirfd, const char *name,
> >               ret = unlinkat(map_dirfd, name, 0);
> >               close_preserve_errno(map_dirfd);
> >               if (ret < 0 && errno != ENOENT) {
> > -                goto err_out;
> > +                return -1;
> >               }
> >           } else if (errno != ENOENT) {
> > -            goto err_out;
> > +            return -1;
> >           }
> >       }
> >   
> > -    ret = unlinkat(dirfd, name, flags);
> > -err_out:
> > -    return ret;
> > +    return unlinkat(dirfd, name, flags);
> >   }
> >   
> >   static int local_remove(FsContext *ctx, const char *path)