| Message ID | 20171219124234.GH2277@quack2.suse.cz (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
On Tue, Dec 19 2017, Jan Kara wrote: > On Fri 08-12-17 13:17:31, NeilBrown wrote: >> On Thu, Dec 07 2017, Amir Goldstein wrote: >> >> > On Thu, Dec 7, 2017 at 5:20 AM, NeilBrown <neilb@suse.com> wrote: >> >> On Wed, Dec 06 2017, Linus Torvalds wrote: >> >> >> >>> On Thu, Nov 30, 2017 at 12:56 PM, NeilBrown <neilb@suse.com> wrote: >> >>>> >> >>>> -/* limit the handle size to NFSv4 handle size now */ >> >>>> -#define MAX_HANDLE_SZ 128 >> >>>> +/* Must be larger than NFSv4 file handle, but small >> >>>> + * enough for an on-stack allocation. overlayfs doesn't >> >>>> + * want this too close to 255. >> >>>> + */ >> >>>> +#define MAX_HANDLE_SZ 200 >> >>> >> >>> This really smells for so many reasons. >> >>> >> >>> Also, that really is starting to be a fairly big stack allocation, and >> >>> it seems to be used in exactly one place (show_mark_fhandle), which >> >>> makes me go "why is that on the stack anyway?". >> >>> >> >>> Could we just allocate a buffer at open time or something? >> >>> >> >>> Linus >> >> >> >> "open time" would be when /proc/X/fdinfo/Y was opened in >> >> seq_fdinfo_open(), and allocating a file_handle there seems a bit odd. >> >> >> >> We can allocate in fs/notify/fdinfo.c:show_fdinfo() which is >> >> the earliest 'notify' specific code to run. There is no >> >> opportunity to return an error but GFP_KERNEL allocations under 1 page >> >> never fail.. >> >> >> >> This patch allocates a single buffer for all inodes reported for a given >> >> inotify fdinfo, and if the allocation files, the filehandle is silently >> >> left blank. More surgery would be needed to be able to return an error. >> >> >> >> Is that at all suitable? >> >> >> >> Thanks, >> >> NeilBrown >> >> >> >> From: NeilBrown <neilb@suse.com> >> >> Subject: fs/notify: don't put file handle buffer on stack. >> >> >> >> A file handle buffer is not tiny, and could need to be larger in future, >> >> so it isn't safe to allocate one on the stack. Instead, we need to >> >> kmalloc(). >> >> >> >> There is no way to return an error status from a ->show_fdinfo() >> >> function, so if the kmalloc fails, we silently exclude the filehandle >> >> from the output. As it is at the end of line, this shouldn't >> >> upset parsing too much. >> > >> > It shouldn't upset parsing because that would be the same out >> > output as without CONFIG_EXPORTFS. AFAIK this information >> > is used by CRUI. >> > >> >> >> >> Signed-off-by: NeilBrown <neilb@suse.com> >> >> >> >> diff --git a/fs/notify/fdinfo.c b/fs/notify/fdinfo.c >> >> index d478629c728b..20d863b9ae16 100644 >> >> --- a/fs/notify/fdinfo.c >> >> +++ b/fs/notify/fdinfo.c >> >> @@ -23,56 +23,58 @@ >> >> >> >> static void show_fdinfo(struct seq_file *m, struct file *f, >> >> void (*show)(struct seq_file *m, >> >> - struct fsnotify_mark *mark)) >> >> + struct fsnotify_mark *mark, >> >> + struct fid *fh)) >> >> { >> >> struct fsnotify_group *group = f->private_data; >> >> struct fsnotify_mark *mark; >> >> + struct fid *fh = kmalloc(MAX_HANDLE_SZ, GFP_KERNEL); >> >> >> >> mutex_lock(&group->mark_mutex); >> >> list_for_each_entry(mark, &group->marks_list, g_list) { >> >> - show(m, mark); >> >> + show(m, mark, fh); >> >> if (seq_has_overflowed(m)) >> >> break; >> >> } >> >> mutex_unlock(&group->mark_mutex); >> >> + kfree(fh); >> >> } >> >> >> >> #if defined(CONFIG_EXPORTFS) >> >> -static void show_mark_fhandle(struct seq_file *m, struct inode *inode) >> >> +static void show_mark_fhandle(struct seq_file *m, struct inode *inode, >> >> + struct fid *fhbuf) >> >> { >> >> - struct { >> >> - struct file_handle handle; >> >> - u8 pad[MAX_HANDLE_SZ]; >> >> - } f; >> >> int size, ret, i; >> >> + unsigned char *bytes; >> >> >> >> - f.handle.handle_bytes = sizeof(f.pad); >> >> - size = f.handle.handle_bytes >> 2; >> >> + if (!fhbuf) >> >> + return; >> >> + size = MAX_HANDLE_SZ >> 2; >> >> >> >> - ret = exportfs_encode_inode_fh(inode, (struct fid *)f.handle.f_handle, &size, 0); >> >> + ret = exportfs_encode_inode_fh(inode, fhbuf, &size, 0); >> >> if ((ret == FILEID_INVALID) || (ret < 0)) { >> >> WARN_ONCE(1, "Can't encode file handler for inotify: %d\n", ret); >> > >> > This WARN_ONCE is out of order. It is perfectly valid for inotify/fanotify >> > to watch over fs that doesn't support exportfs. Care to clean it up? >> > Perhaps a pr_warn_ratelimited() for either !fhbuf or can't encode? >> >> If I were going to clean it up, I would need to do more than remove the >> WARN_ONCE(), which almost certainly never fires. >> >> exportfs_encode_inode_fh() should only be called if sb->s_export_op is >> not NULL. >> When it is NULL, it means that the filesystem doesn't support file >> handles. >> do_sys_name_to_handle() tests this, as does nfsd. But this inotify code >> doesn't. >> So it can report a "file handle" for a file for which file handles >> aren't supported. It will use the default export_encode_fh which >> reports i_ino and i_generation, which may or may not be stable or >> meaningful. >> >> So yes, this code does need a bit of cleaning up.... > > So something like the patch below? > I prefer to fix it in exportfs, as in https://patchwork.kernel.org/patch/10104253/ Thanks, NeilBrown > Honza > -- > Jan Kara <jack@suse.com> > SUSE Labs, CR > From 66a6c05ae2fbe6cfcb24ca3088de39885a6fa5b8 Mon Sep 17 00:00:00 2001 > From: Jan Kara <jack@suse.cz> > Date: Tue, 19 Dec 2017 13:38:54 +0100 > Subject: [PATCH] fsnotify: Do not show file handles for unsupported > filesystems > > Filesystems not setting their s_export_op do not support file handles. > Do no try to encode them using exportfs_encode_inode_fh() since that may > fail or return garbage. > > Reported-by: NeilBrown <neilb@suse.com> > Signed-off-by: Jan Kara <jack@suse.cz> > --- > fs/notify/fdinfo.c | 3 +++ > 1 file changed, 3 insertions(+) > > diff --git a/fs/notify/fdinfo.c b/fs/notify/fdinfo.c > index d478629c728b..041c2b0cc145 100644 > --- a/fs/notify/fdinfo.c > +++ b/fs/notify/fdinfo.c > @@ -46,6 +46,9 @@ static void show_mark_fhandle(struct seq_file *m, struct inode *inode) > } f; > int size, ret, i; > > + if (!inode->i_sb->s_export_op) > + return; > + > f.handle.handle_bytes = sizeof(f.pad); > size = f.handle.handle_bytes >> 2; > > -- > 2.12.3
From 66a6c05ae2fbe6cfcb24ca3088de39885a6fa5b8 Mon Sep 17 00:00:00 2001 From: Jan Kara <jack@suse.cz> Date: Tue, 19 Dec 2017 13:38:54 +0100 Subject: [PATCH] fsnotify: Do not show file handles for unsupported filesystems Filesystems not setting their s_export_op do not support file handles. Do no try to encode them using exportfs_encode_inode_fh() since that may fail or return garbage. Reported-by: NeilBrown <neilb@suse.com> Signed-off-by: Jan Kara <jack@suse.cz> --- fs/notify/fdinfo.c | 3 +++ 1 file changed, 3 insertions(+) diff --git a/fs/notify/fdinfo.c b/fs/notify/fdinfo.c index d478629c728b..041c2b0cc145 100644 --- a/fs/notify/fdinfo.c +++ b/fs/notify/fdinfo.c @@ -46,6 +46,9 @@ static void show_mark_fhandle(struct seq_file *m, struct inode *inode) } f; int size, ret, i; + if (!inode->i_sb->s_export_op) + return; + f.handle.handle_bytes = sizeof(f.pad); size = f.handle.handle_bytes >> 2; -- 2.12.3