Nice catch. The code that exists is confusing due to newinfo->entries being overwritten and then freed in the existing code path as you state in your commit log.
* Wenwen Wang <[email protected]> [190720 08:23]: > From: Wenwen Wang <[email protected]> > > In compat_do_replace(), a temporary buffer is allocated through vmalloc() > to hold entries copied from the user space. The buffer address is firstly > saved to 'newinfo->entries', and later on assigned to 'entries_tmp'. Then > the entries in this temporary buffer is copied to the internal kernel > structure through compat_copy_entries(). If this copy process fails, > compat_do_replace() should be terminated. However, the allocated temporary > buffer is not freed on this path, leading to a memory leak. > > To fix the bug, free the buffer before returning from compat_do_replace(). > > Signed-off-by: Wenwen Wang <[email protected]> > --- > net/bridge/netfilter/ebtables.c | 4 +++- > 1 file changed, 3 insertions(+), 1 deletion(-) > > diff --git a/net/bridge/netfilter/ebtables.c b/net/bridge/netfilter/ebtables.c > index 963dfdc..fd84b48e 100644 > --- a/net/bridge/netfilter/ebtables.c > +++ b/net/bridge/netfilter/ebtables.c > @@ -2261,8 +2261,10 @@ static int compat_do_replace(struct net *net, void > __user *user, > state.buf_kern_len = size64; > > ret = compat_copy_entries(entries_tmp, tmp.entries_size, &state); > - if (WARN_ON(ret < 0)) > + if (WARN_ON(ret < 0)) { > + vfree(entries_tmp); > goto out_unlock; > + } Would it be worth adding a new goto label above out_unlock and free this entries_tmp? It could then be used in previous failure path as well. Thanks, Liam
