| Message ID | 20220913140410.277221532@linuxfoundation.org (mailing list archive) |
|---|---|
| State | Not Applicable |
| Delegated to: | Netdev Maintainers |
| Headers | show |
| Series | None | expand |
On Tue, Sep 13, 2022 at 04:01:51PM +0200, Greg Kroah-Hartman wrote: > From: Greg Kroah-Hartman <gregkh@linuxfoundation.org> > > commit fe2c9c61f668cde28dac2b188028c5299cedcc1e upstream. > > When calling debugfs_lookup() the result must have dput() called on it, > otherwise the memory will leak over time. Fix this up to be much > simpler logic and only create the root debugfs directory once when the > driver is first accessed. That resolves the memory leak and makes > things more obvious as to what the intent is. > > Cc: Marcin Wojtas <mw@semihalf.com> > Cc: Russell King <linux@armlinux.org.uk> > Cc: "David S. Miller" <davem@davemloft.net> > Cc: Eric Dumazet <edumazet@google.com> > Cc: Jakub Kicinski <kuba@kernel.org> > Cc: Paolo Abeni <pabeni@redhat.com> > Cc: netdev@vger.kernel.org > Cc: stable <stable@kernel.org> > Fixes: 21da57a23125 ("net: mvpp2: add a debugfs interface for the Header Parser") > Signed-off-by: David S. Miller <davem@davemloft.net> > Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> > --- > drivers/net/ethernet/marvell/mvpp2/mvpp2_debugfs.c | 4 ++-- > 1 file changed, 2 insertions(+), 2 deletions(-) > > --- a/drivers/net/ethernet/marvell/mvpp2/mvpp2_debugfs.c > +++ b/drivers/net/ethernet/marvell/mvpp2/mvpp2_debugfs.c > @@ -700,10 +700,10 @@ void mvpp2_dbgfs_cleanup(struct mvpp2 *p > > void mvpp2_dbgfs_init(struct mvpp2 *priv, const char *name) > { > - struct dentry *mvpp2_dir, *mvpp2_root; > + static struct dentry *mvpp2_root; > + struct dentry *mvpp2_dir; > int ret, i; > > - mvpp2_root = debugfs_lookup(MVPP2_DRIVER_NAME, NULL); > if (!mvpp2_root) > mvpp2_root = debugfs_create_dir(MVPP2_DRIVER_NAME, NULL); This looks broken to me. What happens if this is built as a module, and the module is loaded, binds (and creates the directory), then is removed, and then re- inserted? Nothing removes the old directory, so doesn't debugfs_create_dir() fail, resulting in subsequent failure to add any subsequent debugfs entries? I don't think this patch should be backported to stable trees until this point is addressed.
On Tue, Sep 13, 2022 at 05:48:58PM +0100, Russell King (Oracle) wrote: > On Tue, Sep 13, 2022 at 04:01:51PM +0200, Greg Kroah-Hartman wrote: > > From: Greg Kroah-Hartman <gregkh@linuxfoundation.org> > > > > commit fe2c9c61f668cde28dac2b188028c5299cedcc1e upstream. > > > > When calling debugfs_lookup() the result must have dput() called on it, > > otherwise the memory will leak over time. Fix this up to be much > > simpler logic and only create the root debugfs directory once when the > > driver is first accessed. That resolves the memory leak and makes > > things more obvious as to what the intent is. > > > > Cc: Marcin Wojtas <mw@semihalf.com> > > Cc: Russell King <linux@armlinux.org.uk> > > Cc: "David S. Miller" <davem@davemloft.net> > > Cc: Eric Dumazet <edumazet@google.com> > > Cc: Jakub Kicinski <kuba@kernel.org> > > Cc: Paolo Abeni <pabeni@redhat.com> > > Cc: netdev@vger.kernel.org > > Cc: stable <stable@kernel.org> > > Fixes: 21da57a23125 ("net: mvpp2: add a debugfs interface for the Header Parser") > > Signed-off-by: David S. Miller <davem@davemloft.net> > > Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> > > --- > > drivers/net/ethernet/marvell/mvpp2/mvpp2_debugfs.c | 4 ++-- > > 1 file changed, 2 insertions(+), 2 deletions(-) > > > > --- a/drivers/net/ethernet/marvell/mvpp2/mvpp2_debugfs.c > > +++ b/drivers/net/ethernet/marvell/mvpp2/mvpp2_debugfs.c > > @@ -700,10 +700,10 @@ void mvpp2_dbgfs_cleanup(struct mvpp2 *p > > > > void mvpp2_dbgfs_init(struct mvpp2 *priv, const char *name) > > { > > - struct dentry *mvpp2_dir, *mvpp2_root; > > + static struct dentry *mvpp2_root; > > + struct dentry *mvpp2_dir; > > int ret, i; > > > > - mvpp2_root = debugfs_lookup(MVPP2_DRIVER_NAME, NULL); > > if (!mvpp2_root) > > mvpp2_root = debugfs_create_dir(MVPP2_DRIVER_NAME, NULL); > > This looks broken to me. > > What happens if this is built as a module, and the module is loaded, > binds (and creates the directory), then is removed, and then re- > inserted? Nothing removes the old directory, so doesn't > debugfs_create_dir() fail, resulting in subsequent failure to add > any subsequent debugfs entries? > > I don't think this patch should be backported to stable trees until > this point is addressed. I'll drop this for now and get back to the fixup next week. thanks, greg k-h
--- a/drivers/net/ethernet/marvell/mvpp2/mvpp2_debugfs.c +++ b/drivers/net/ethernet/marvell/mvpp2/mvpp2_debugfs.c @@ -700,10 +700,10 @@ void mvpp2_dbgfs_cleanup(struct mvpp2 *p void mvpp2_dbgfs_init(struct mvpp2 *priv, const char *name) { - struct dentry *mvpp2_dir, *mvpp2_root; + static struct dentry *mvpp2_root; + struct dentry *mvpp2_dir; int ret, i; - mvpp2_root = debugfs_lookup(MVPP2_DRIVER_NAME, NULL); if (!mvpp2_root) mvpp2_root = debugfs_create_dir(MVPP2_DRIVER_NAME, NULL);