[PATCH] netfilter: fix possible ZERO_SIZE_PTR pointer dereferencing error.

Since we cannot make sure the 'hook_mask' will always be none zero
here. If it equals to zero, the num_hooks will be zero too, and then
kmalloc() will return ZERO_SIZE_PTR, which is (void *)16.

Then the following error check will fails:
  ops = kmalloc(sizeof(*ops) * num_hooks, GFP_KERNEL);
  if (ops == NULL)
          return ERR_PTR(-ENOMEM);

So this patch fix this with just doing the zero check before calling
kmalloc() is called.

Maybe the case above will never happen here, but in theory.

Signed-off-by: Xiubo Li <redacted>
---
 net/netfilter/x_tables.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/net/netfilter/x_tables.c b/net/netfilter/x_tables.c
index c8a0b7d..4df8e38 100644
--- a/net/netfilter/x_tables.c
+++ b/net/netfilter/x_tables.c

@@ -1185,6 +1185,9 @@ struct nf_hook_ops *xt_hook_link(const struct xt_table *table, nf_hookfn *fn)
 	struct nf_hook_ops *ops;
 	int ret;
 
+	if (!num_hooks)
+		return ERR_PTR(-EINVAL);
+
 	ops = kmalloc(sizeof(*ops) * num_hooks, GFP_KERNEL);
 	if (ops == NULL)
 		return ERR_PTR(-ENOMEM);

-- 
1.8.3.1

On Wed, Jun 01, 2016 at 04:34:28PM +0800, Xiubo Li wrote:

What kernel version are you using? I don't see xt_hook_link() in the
development tree.

 	struct nf_hook_ops *ops;
 	int ret;
 
+	if (!num_hooks)
+		return ERR_PTR(-EINVAL);
+
 	ops = kmalloc(sizeof(*ops) * num_hooks, GFP_KERNEL);
 	if (ops == NULL)
 		return ERR_PTR(-ENOMEM);
-- 
1.8.3.1

quoted

  net/netfilter/x_tables.c | 3 +++
  1 file changed, 3 insertions(+)

diff --git a/net/netfilter/x_tables.c b/net/netfilter/x_tables.c
index c8a0b7d..4df8e38 100644
--- a/net/netfilter/x_tables.c
+++ b/net/netfilter/x_tables.c

@@ -1185,6 +1185,9 @@ struct nf_hook_ops *xt_hook_link(const struct xt_table *table, nf_hookfn *fn)

What kernel version are you using? I don't see xt_hook_link() in the
development tree.

Sorry, in the wrong tree, i just work on linux-next tree, forget to 
checkout the newest tags.

Should I will use nf.git tree or others instead ?

Thanks very much.

BRs
Xiubo Li

On Wed, Jun 01, 2016 at 05:52:59PM +0800, Xiubo Li wrote:

quoted

quoted

 net/netfilter/x_tables.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/net/netfilter/x_tables.c b/net/netfilter/x_tables.c
index c8a0b7d..4df8e38 100644
--- a/net/netfilter/x_tables.c
+++ b/net/netfilter/x_tables.c

@@ -1185,6 +1185,9 @@ struct nf_hook_ops *xt_hook_link(const struct xt_table *table, nf_hookfn *fn)

What kernel version are you using? I don't see xt_hook_link() in the
development tree.

Sorry, in the wrong tree, i just work on linux-next tree, forget to checkout
the newest tags.

Should I will use nf.git tree or others instead ?

Yes please, thanks.

On 01/06/2016 19:04, Pablo Neira Ayuso wrote:

On Wed, Jun 01, 2016 at 05:52:59PM +0800, Xiubo Li wrote:

quoted

quoted

quoted

  net/netfilter/x_tables.c | 3 +++
  1 file changed, 3 insertions(+)

diff --git a/net/netfilter/x_tables.c b/net/netfilter/x_tables.c
index c8a0b7d..4df8e38 100644
--- a/net/netfilter/x_tables.c
+++ b/net/netfilter/x_tables.c

@@ -1185,6 +1185,9 @@ struct nf_hook_ops *xt_hook_link(const struct xt_table *table, nf_hookfn *fn)

What kernel version are you using? I don't see xt_hook_link() in the
development tree.

Sorry, in the wrong tree, i just work on linux-next tree, forget to checkout
the newest tags.

Should I will use nf.git tree or others instead ?

Yes please, thanks.

Okay.

Thanks,

BRs
Xiubo Li