Stefan Kempf wrote:
> Martin Pieuchot wrote:
> > On 28/02/16(Sun) 13:14, Martin Natano wrote:
> > > The ext2fs_read() and ffs_read() functions return EFBIG when uio_offset
> > > if smaller than zero or larger than the maxium file size. However this
> > > doesn't seem to be in accordance with the POSIX read(2) specification,
> > > which requires EINVAL for an invalid offset (< 2) and a return of 0
> > > (zero bytes transferred) for an offset that's at or paste the EOF. EFBIG
> > > actually means "File too large", which is clearly not true in both
> > > cases.
> >
> > This seems to be coherent with MSDOSFS.
> >
> > I'm also wondering when you say "an offset that's at or paste the
> > EOF" does that include ``uio_resid''? I mean shouldn't you check
> > for:
> >
> > if ((uio->uio_offset + uio->uio_resid) > fs->fs_maxfilesize)
> > ...
>
> I think if uio->uio_offset < fs->fs_maxfilesize, then
> min(uio->uio_resid, fs->fs_maxfilesize - uio->uio_offset)
> bytes should be read.
Ehh. Not quite true. It can't read more than the size of the file.
The read-loops of ffs_read and ext2_ind_read already check
whether uio_offset is beyond the size of the file:
for (error = 0, bp = NULL; uio->uio_resid > 0; bp = NULL) {
if ((bytesinfile = DIP(ip, size) - uio->uio_offset) <= 0)
break;
If we are assured that DIP(ip, size) cannot return a bogus size
(> fs->fs_maxfilesize), the check before the loop could be
if (uio->uio_offset >= DIP(ip, size) || uio->uio_resid == 0)
return (0);
> Maybe the check should be if (uio_offset >= fs->fs_maxfilesize)
> though. Otherwise access flags of the inode are changed at the end
> if ext2_ind_read() and ffs_read() even though there was no real access.
>
> > > Index: ufs/ext2fs/ext2fs_readwrite.c
> > > ===================================================================
> > > RCS file: /cvs/src/sys/ufs/ext2fs/ext2fs_readwrite.c,v
> > > retrieving revision 1.39
> > > diff -u -p -r1.39 ext2fs_readwrite.c
> > > --- ufs/ext2fs/ext2fs_readwrite.c 27 Feb 2016 18:50:38 -0000 1.39
> > > +++ ufs/ext2fs/ext2fs_readwrite.c 28 Feb 2016 09:10:16 -0000
> > > @@ -100,9 +100,9 @@ ext2_ind_read(struct vnode *vp, struct i
> > > } else if (vp->v_type != VREG && vp->v_type != VDIR)
> > > panic("%s: type %d", "ext2fs_read", vp->v_type);
> > > #endif
> > > - if (e2fs_overflow(fs, 0, uio->uio_offset))
> > > - return (EFBIG);
> > > - if (uio->uio_resid == 0)
> > > + if (uio->uio_offset < 0)
> > > + return (EINVAL);
> > > + if (uio->uio_offset > fs->e2fs_maxfilesize || uio->uio_resid == 0)
> > > return (0);
> > >
> > > for (error = 0, bp = NULL; uio->uio_resid > 0; bp = NULL) {
> > > @@ -163,7 +163,6 @@ ext4_ext_read(struct vnode *vp, struct i
> > > struct ext4_extent_path path;
> > > struct ext4_extent nex, *ep;
> > > struct buf *bp;
> > > - size_t orig_resid;
> > > daddr_t lbn, pos;
> > > off_t bytesinfile;
> > > int size, xfersize, blkoffset;
> > > @@ -171,12 +170,10 @@ ext4_ext_read(struct vnode *vp, struct i
> > >
> > > memset(&path, 0, sizeof path);
> > >
> > > - orig_resid = uio->uio_resid;
> > > - if (orig_resid == 0)
> > > + if (uio->uio_offset < 0)
> > > + return (EINVAL);
> > > + if (uio->uio_offset > fs->e2fs_maxfilesize || uio->uio_resid == 0)
> > > return (0);
> > > -
> > > - if (e2fs_overflow(fs, 0, uio->uio_offset))
> > > - return (EFBIG);
> > >
> > > while (uio->uio_resid > 0) {
> > > if ((bytesinfile = ext2fs_size(ip) - uio->uio_offset) <= 0)
> > > Index: ufs/ffs/ffs_vnops.c
> > > ===================================================================
> > > RCS file: /cvs/src/sys/ufs/ffs/ffs_vnops.c,v
> > > retrieving revision 1.84
> > > diff -u -p -r1.84 ffs_vnops.c
> > > --- ufs/ffs/ffs_vnops.c 27 Feb 2016 18:50:38 -0000 1.84
> > > +++ ufs/ffs/ffs_vnops.c 28 Feb 2016 09:10:16 -0000
> > > @@ -214,10 +214,9 @@ ffs_read(void *v)
> > > panic("ffs_read: type %d", vp->v_type);
> > > #endif
> > > fs = ip->i_fs;
> > > - if ((u_int64_t)uio->uio_offset > fs->fs_maxfilesize)
> > > - return (EFBIG);
> > > -
> > > - if (uio->uio_resid == 0)
> > > + if (uio->uio_offset < 0)
> > > + return (EINVAL);
> > > + if (uio->uio_offset > fs->fs_maxfilesize || uio->uio_resid == 0)
> > > return (0);
> > >
> > > for (error = 0, bp = NULL; uio->uio_resid > 0; bp = NULL) {
> > >
> >
