| Message ID | 20240705081642.12032-1-ed.tsai@mediatek.com (mailing list archive) |
|---|---|
| State | New |
| Headers | show |
| Series | [1/1] backing-file: covert to using fops->splice_write | expand |
On Fri, 2024-07-05 at 16:16 +0800, ed.tsai@mediatek.com wrote: > From: Ed Tsai <ed.tsai@mediatek.com> > > Filesystems may define their own splice write. Therefore, use file > fops instead of invoking iter_file_splice_write() directly. > > Signed-off-by: Ed Tsai <ed.tsai@mediatek.com> > --- > fs/backing-file.c | 5 ++++- > 1 file changed, 4 insertions(+), 1 deletion(-) > > diff --git a/fs/backing-file.c b/fs/backing-file.c > index 740185198db3..687a7fae7d25 100644 > --- a/fs/backing-file.c > +++ b/fs/backing-file.c > @@ -280,13 +280,16 @@ ssize_t backing_file_splice_write(struct > pipe_inode_info *pipe, > if (WARN_ON_ONCE(!(out->f_mode & FMODE_BACKING))) > return -EIO; > > + if (out->f_op->splice_write) > + return -EINVAL; > + > ret = file_remove_privs(ctx->user_file); > if (ret) > return ret; > > old_cred = override_creds(ctx->cred); > file_start_write(out); > - ret = iter_file_splice_write(pipe, out, ppos, len, flags); > + ret = out->f_op->splice_write(pipe, out, ppos, len, flags); > file_end_write(out); > revert_creds(old_cred); > s/covert/convert/ for subject
On Fri, Jul 5, 2024 at 11:17 AM <ed.tsai@mediatek.com> wrote: > > From: Ed Tsai <ed.tsai@mediatek.com> > > Filesystems may define their own splice write. Therefore, use file > fops instead of invoking iter_file_splice_write() directly. This looks sane, but can you share the scenario where you ran into this? or did you find this via code audit? I can think of these cases: 1. overlayfs with fuse (virtiofs) upper 2. fuse passthrough over fuse 3. fuse passthrough over overlayfs 4. fuse passthrough over gfs2 or some out of tree fs The first two will not cause any harm, In case #3, according to the comment above ovl_splice_write() the current code could even deadlock. So do you have a reproduction? Thanks, Amir. > > Signed-off-by: Ed Tsai <ed.tsai@mediatek.com> > --- > fs/backing-file.c | 5 ++++- > 1 file changed, 4 insertions(+), 1 deletion(-) > > diff --git a/fs/backing-file.c b/fs/backing-file.c > index 740185198db3..687a7fae7d25 100644 > --- a/fs/backing-file.c > +++ b/fs/backing-file.c > @@ -280,13 +280,16 @@ ssize_t backing_file_splice_write(struct pipe_inode_info *pipe, > if (WARN_ON_ONCE(!(out->f_mode & FMODE_BACKING))) > return -EIO; > > + if (out->f_op->splice_write) > + return -EINVAL; > + > ret = file_remove_privs(ctx->user_file); > if (ret) > return ret; > > old_cred = override_creds(ctx->cred); > file_start_write(out); > - ret = iter_file_splice_write(pipe, out, ppos, len, flags); > + ret = out->f_op->splice_write(pipe, out, ppos, len, flags); > file_end_write(out); > revert_creds(old_cred); > > -- > 2.18.0 >
On Fri, Jul 05, 2024 at 04:16:39PM +0800, ed.tsai@mediatek.com wrote: > +++ b/fs/backing-file.c > @@ -280,13 +280,16 @@ ssize_t backing_file_splice_write(struct pipe_inode_info *pipe, > if (WARN_ON_ONCE(!(out->f_mode & FMODE_BACKING))) > return -EIO; > > + if (out->f_op->splice_write) > + return -EINVAL; Umm ... shouldn't this have been !out->f_op->splice_write? > ret = file_remove_privs(ctx->user_file); > if (ret) > return ret; > > old_cred = override_creds(ctx->cred); > file_start_write(out); > - ret = iter_file_splice_write(pipe, out, ppos, len, flags); > + ret = out->f_op->splice_write(pipe, out, ppos, len, flags); > file_end_write(out); > revert_creds(old_cred); > > -- > 2.18.0 > >
On Fri, 2024-07-05 at 15:27 +0300, Amir Goldstein wrote: > > External email : Please do not click links or open attachments until > you have verified the sender or the content. > On Fri, Jul 5, 2024 at 11:17 AM <ed.tsai@mediatek.com> wrote: > > > > From: Ed Tsai <ed.tsai@mediatek.com> > > > > Filesystems may define their own splice write. Therefore, use file > > fops instead of invoking iter_file_splice_write() directly. > > This looks sane, but can you share the scenario where you ran into > this? > or did you find this via code audit? > > I can think of these cases: > 1. overlayfs with fuse (virtiofs) upper > 2. fuse passthrough over fuse > 3. fuse passthrough over overlayfs > 4. fuse passthrough over gfs2 or some out of tree fs > > The first two will not cause any harm, > In case #3, according to the comment above ovl_splice_write() > the current code could even deadlock. > > So do you have a reproduction? > > Thanks, > Amir. I came across this while checking what's new in the next LTS kernel. This appears to be taken from overlayfs, and currently, no one has encountered any issus about this. On Sun, 2024-07-07 at 21:42 +0100, Matthew Wilcox wrote: > On Fri, Jul 05, 2024 at 04:16:39PM +0800, ed.tsai@mediatek.com wrote: > > +++ b/fs/backing-file.c > > @@ -280,13 +280,16 @@ ssize_t backing_file_splice_write(struct > pipe_inode_info *pipe, > > if (WARN_ON_ONCE(!(out->f_mode & FMODE_BACKING))) > > return -EIO; > > > > +if (out->f_op->splice_write) > > +return -EINVAL; > > Umm ... shouldn't this have been !out->f_op->splice_write? > OMG... This is the wrong version. I will send the correct on later. > > ret = file_remove_privs(ctx->user_file); > > if (ret) > > return ret; > > > > old_cred = override_creds(ctx->cred); > > file_start_write(out); > > -ret = iter_file_splice_write(pipe, out, ppos, len, flags); > > +ret = out->f_op->splice_write(pipe, out, ppos, len, flags); > > file_end_write(out); > > revert_creds(old_cred); > > > > -- > > 2.18.0 > > > > >
diff --git a/fs/backing-file.c b/fs/backing-file.c index 740185198db3..687a7fae7d25 100644 --- a/fs/backing-file.c +++ b/fs/backing-file.c @@ -280,13 +280,16 @@ ssize_t backing_file_splice_write(struct pipe_inode_info *pipe, if (WARN_ON_ONCE(!(out->f_mode & FMODE_BACKING))) return -EIO; + if (out->f_op->splice_write) + return -EINVAL; + ret = file_remove_privs(ctx->user_file); if (ret) return ret; old_cred = override_creds(ctx->cred); file_start_write(out); - ret = iter_file_splice_write(pipe, out, ppos, len, flags); + ret = out->f_op->splice_write(pipe, out, ppos, len, flags); file_end_write(out); revert_creds(old_cred);