[PATCH net] netfilter: x_tables: avoid out-of-bounds reads in xt_request_find_match()

[PATCH net] netfilter: x_tables: avoid out-of-bounds reads in xt_request_find_match()

[Eric Dumazet]

From: Eric Dumazet <edumazet@google.com>

It looks like syzbot found its way into netfilter territory.

Issue here is that @name comes from user space and might
not be null terminated.

Out-of-bound reads happen, KASAN is not happy.

Signed-off-by: Eric Dumazet <edumazet@google.com>
Reported-by: syzbot <syzkaller@googlegroups.com>
---
No Fixes: tag, bug seems to be a day-0 one.

diff --git a/net/netfilter/x_tables.c b/net/netfilter/x_tables.c
index 55802e97f906d1987ed78b4296584deb38e5f876..8516dc459b539342f44d2b2b3e21b140677c7826 100644
--- a/net/netfilter/x_tables.c
+++ b/net/netfilter/x_tables.c
@@ -210,6 +210,9 @@ xt_request_find_match(uint8_t nfproto, const char *name, uint8_t revision)
 {
 	struct xt_match *match;
 
+	if (strnlen(name, XT_EXTENSION_MAXNAMELEN) == XT_EXTENSION_MAXNAMELEN)
+		return ERR_PTR(-EINVAL);
+
 	match = xt_find_match(nfproto, name, revision);
 	if (IS_ERR(match)) {
 		request_module("%st_%s", xt_prefix[nfproto], name);

Re: [PATCH net] netfilter: x_tables: avoid out-of-bounds reads in xt_request_find_match()

[Florian Westphal]

Eric Dumazet <eric.dumazet@gmail.com> wrote:
> From: Eric Dumazet <edumazet@google.com>
> 
> It looks like syzbot found its way into netfilter territory.

Excellent.  This will sure allow to find and fix more bugs :-)

> Issue here is that @name comes from user space and might
> not be null terminated.

Indeed, thanks for fixing this Eric.

xt_find_target() and xt_find_table_lock() might have similar issues.

Re: [PATCH net] netfilter: x_tables: avoid out-of-bounds reads in xt_request_find_match()

[Pablo Neira Ayuso]

On Wed, Jan 24, 2018 at 02:49:48PM -0800, Eric Dumazet wrote:
> From: Eric Dumazet <edumazet@google.com>
> 
> It looks like syzbot found its way into netfilter territory.
> 
> Issue here is that @name comes from user space and might
> not be null terminated.
> 
> Out-of-bound reads happen, KASAN is not happy.

Applied, thanks Eric.

Re: [PATCH net] netfilter: x_tables: avoid out-of-bounds reads in xt_request_find_match()

[Pablo Neira Ayuso]

On Thu, Jan 25, 2018 at 12:19:52AM +0100, Florian Westphal wrote:
> Eric Dumazet <eric.dumazet@gmail.com> wrote:
> > From: Eric Dumazet <edumazet@google.com>
> > 
> > It looks like syzbot found its way into netfilter territory.
> 
> Excellent.  This will sure allow to find and fix more bugs :-)
> 
> > Issue here is that @name comes from user space and might
> > not be null terminated.
> 
> Indeed, thanks for fixing this Eric.
> 
> xt_find_target() and xt_find_table_lock() might have similar issues.

I'm going to keep back this patch then, it would be good if we can
find this in one single patch.

Thanks.

Re: [PATCH net] netfilter: x_tables: avoid out-of-bounds reads in xt_request_find_match()

[Pablo Neira Ayuso]

On Thu, Jan 25, 2018 at 12:50:56AM +0100, Pablo Neira Ayuso wrote:
> On Thu, Jan 25, 2018 at 12:19:52AM +0100, Florian Westphal wrote:
> > Eric Dumazet <eric.dumazet@gmail.com> wrote:
> > > From: Eric Dumazet <edumazet@google.com>
> > > 
> > > It looks like syzbot found its way into netfilter territory.
> > 
> > Excellent.  This will sure allow to find and fix more bugs :-)
> > 
> > > Issue here is that @name comes from user space and might
> > > not be null terminated.
> > 
> > Indeed, thanks for fixing this Eric.
> > 
> > xt_find_target() and xt_find_table_lock() might have similar issues.
> 
> I'm going to keep back this patch then, it would be good if we can
> find this in one single patch.

s/find/fix/

Sorry.

Re: [PATCH net] netfilter: x_tables: avoid out-of-bounds reads in xt_request_find_match()

[Eric Dumazet]

On Thu, 2018-01-25 at 01:13 +0100, Pablo Neira Ayuso wrote:
> On Thu, Jan 25, 2018 at 12:50:56AM +0100, Pablo Neira Ayuso wrote:
> > On Thu, Jan 25, 2018 at 12:19:52AM +0100, Florian Westphal wrote:
> > > Eric Dumazet <eric.dumazet@gmail.com> wrote:
> > > > From: Eric Dumazet <edumazet@google.com>
> > > > 
> > > > It looks like syzbot found its way into netfilter territory.
> > > 
> > > Excellent.  This will sure allow to find and fix more bugs :-)
> > > 
> > > > Issue here is that @name comes from user space and might
> > > > not be null terminated.
> > > 
> > > Indeed, thanks for fixing this Eric.
> > > 
> > > xt_find_target() and xt_find_table_lock() might have similar issues.
> > 
> > I'm going to keep back this patch then, it would be good if we can
> > find this in one single patch.
> 
> s/find/fix/
> 
> Sorry.


Ok, but apparently you partially fixed this recently :/

Commits 78b79876761b8 and b301f25387599 took care of
xt_find_table_lock() it seems.

I'll send a V2 including xt_request_find_target()

[PATCH v2 net] netfilter: x_tables: avoid out-of-bounds reads in xt_request_find_{match|target}

[Eric Dumazet]

From: Eric Dumazet <edumazet@google.com>

It looks like syzbot found its way into netfilter territory.

Issue here is that @name comes from user space and might
not be null terminated.

Out-of-bound reads happen, KASAN is not happy.

v2 added similar fix for xt_request_find_target(),
as Florian advised.

Signed-off-by: Eric Dumazet <edumazet@google.com>
Reported-by: syzbot <syzkaller@googlegroups.com>
---
No Fixes: tag, bug seems to be a day-0 one.

 net/netfilter/x_tables.c |    6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/net/netfilter/x_tables.c b/net/netfilter/x_tables.c
index 55802e97f906d1987ed78b4296584deb38e5f876..ecffc51ce83b07c063a0db67cdb33d9bf48a75ac 100644
--- a/net/netfilter/x_tables.c
+++ b/net/netfilter/x_tables.c
@@ -210,6 +210,9 @@ xt_request_find_match(uint8_t nfproto, const char *name, uint8_t revision)
 {
 	struct xt_match *match;
 
+	if (strnlen(name, XT_EXTENSION_MAXNAMELEN) == XT_EXTENSION_MAXNAMELEN)
+		return ERR_PTR(-EINVAL);
+
 	match = xt_find_match(nfproto, name, revision);
 	if (IS_ERR(match)) {
 		request_module("%st_%s", xt_prefix[nfproto], name);
@@ -252,6 +255,9 @@ struct xt_target *xt_request_find_target(u8 af, const char *name, u8 revision)
 {
 	struct xt_target *target;
 
+	if (strnlen(name, XT_EXTENSION_MAXNAMELEN) == XT_EXTENSION_MAXNAMELEN)
+		return ERR_PTR(-EINVAL);
+
 	target = xt_find_target(af, name, revision);
 	if (IS_ERR(target)) {
 		request_module("%st_%s", xt_prefix[af], name);

Re: [PATCH v2 net] netfilter: x_tables: avoid out-of-bounds reads in xt_request_find_{match|target}

[Florian Westphal]

Eric Dumazet <eric.dumazet@gmail.com> wrote:
> From: Eric Dumazet <edumazet@google.com>
> 
> It looks like syzbot found its way into netfilter territory.
> 
> Issue here is that @name comes from user space and might
> not be null terminated.
> 
> Out-of-bound reads happen, KASAN is not happy.
> 
> v2 added similar fix for xt_request_find_target(),
> as Florian advised.
> 
> Signed-off-by: Eric Dumazet <edumazet@google.com>
> Reported-by: syzbot <syzkaller@googlegroups.com>

Thanks a lot Eric!

Acked-by: Florian Westphal <fw@strlen.de>

Re: [PATCH v2 net] netfilter: x_tables: avoid out-of-bounds reads in xt_request_find_{match|target}

[Pablo Neira Ayuso]

On Wed, Jan 24, 2018 at 05:16:09PM -0800, Eric Dumazet wrote:
> From: Eric Dumazet <edumazet@google.com>
> 
> It looks like syzbot found its way into netfilter territory.
> 
> Issue here is that @name comes from user space and might
> not be null terminated.
> 
> Out-of-bound reads happen, KASAN is not happy.
> 
> v2 added similar fix for xt_request_find_target(),
> as Florian advised.

Applied, thanks Eric.