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;
+ }
vfree(entries_tmp);
tmp.entries_size = size64;
--
2.7.4
Wenwen Wang <[email protected]> wrote:
> 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]>
Reviewed-by: Florian Westphal <[email protected]>
On Sat, Jul 20, 2019 at 07:22:45AM -0500, Wenwen Wang wrote:
> 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().
Applied, thanks.
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
On Mon, Jul 22, 2019 at 7:34 AM Liam R. Howlett <[email protected]> wrote:
>
> 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.
Yes, that would make the code much clearer and easier to understand.
Thanks!
Wenwen