[PATCH net] ipv4: Check attribute length for RTA_GATEWAY

Subsystems: networking [general], networking [ipv4/ipv6], the rest

STALE1773d

4 messages, 3 authors, 2021-12-12 · open the first message on its own page

[PATCH net] ipv4: Check attribute length for RTA_GATEWAY

From: David Ahern <dsahern@kernel.org>
Date: 2021-12-11 16:21:56

syzbot reported uninit-value:
============================================================
  BUG: KMSAN: uninit-value in fib_get_nhs+0xac4/0x1f80
  net/ipv4/fib_semantics.c:708
   fib_get_nhs+0xac4/0x1f80 net/ipv4/fib_semantics.c:708
   fib_create_info+0x2411/0x4870 net/ipv4/fib_semantics.c:1453
   fib_table_insert+0x45c/0x3a10 net/ipv4/fib_trie.c:1224
   inet_rtm_newroute+0x289/0x420 net/ipv4/fib_frontend.c:886

Add length checking before using the attribute.

Fixes: 4e902c57417c ("[IPv4]: FIB configuration using struct fib_config")
Reported-by: syzbot+d4b9a2851cc3ce998741@syzkaller.appspotmail.com
Signed-off-by: David Ahern <dsahern@kernel.org>
Cc: Thomas Graf <tgraf@suug.ch>
---
I do not have KMSAN setup, so this is based on a code analysis. Before
4e902c57417c fib_get_attr32 was checking the attribute length; the
switch to nla_get_u32 does not.

 net/ipv4/fib_semantics.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/net/ipv4/fib_semantics.c b/net/ipv4/fib_semantics.c
index 3cad543dc747..930843ba3b17 100644
--- a/net/ipv4/fib_semantics.c
+++ b/net/ipv4/fib_semantics.c

@@ -704,6 +704,10 @@ static int fib_get_nhs(struct fib_info *fi, struct rtnexthop *rtnh,
 				return -EINVAL;
 			}
 			if (nla) {
+				if (nla_len(nla) < sizeof(__be32)) {
+					NL_SET_ERR_MSG(extack, "Invalid IPv4 address in RTA_GATEWAY");
+					return -EINVAL;
+				}
 				fib_cfg.fc_gw4 = nla_get_in_addr(nla);
 				if (fib_cfg.fc_gw4)
 					fib_cfg.fc_gw_family = AF_INET;

-- 
2.24.3 (Apple Git-128)

Re: [PATCH net] ipv4: Check attribute length for RTA_GATEWAY

From: Ido Schimmel <hidden>
Date: 2021-12-11 19:13:47

On Sat, Dec 11, 2021 at 09:21:48AM -0700, David Ahern wrote:

syzbot reported uninit-value:
============================================================
  BUG: KMSAN: uninit-value in fib_get_nhs+0xac4/0x1f80
  net/ipv4/fib_semantics.c:708
   fib_get_nhs+0xac4/0x1f80 net/ipv4/fib_semantics.c:708
   fib_create_info+0x2411/0x4870 net/ipv4/fib_semantics.c:1453
   fib_table_insert+0x45c/0x3a10 net/ipv4/fib_trie.c:1224
   inet_rtm_newroute+0x289/0x420 net/ipv4/fib_frontend.c:886

Add length checking before using the attribute.

Fixes: 4e902c57417c ("[IPv4]: FIB configuration using struct fib_config")
Reported-by: syzbot+d4b9a2851cc3ce998741@syzkaller.appspotmail.com
Signed-off-by: David Ahern <dsahern@kernel.org>
Cc: Thomas Graf <tgraf@suug.ch>
---
I do not have KMSAN setup, so this is based on a code analysis. Before

Was using this in the past:
https://github.com/google/syzkaller/blob/master/docs/syzbot.md#kmsan-bugs

quoted hunk

4e902c57417c fib_get_attr32 was checking the attribute length; the
switch to nla_get_u32 does not.

 net/ipv4/fib_semantics.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/net/ipv4/fib_semantics.c b/net/ipv4/fib_semantics.c
index 3cad543dc747..930843ba3b17 100644
--- a/net/ipv4/fib_semantics.c
+++ b/net/ipv4/fib_semantics.c

@@ -704,6 +704,10 @@ static int fib_get_nhs(struct fib_info *fi, struct rtnexthop *rtnh,
 				return -EINVAL;
 			}
 			if (nla) {
+				if (nla_len(nla) < sizeof(__be32)) {
+					NL_SET_ERR_MSG(extack, "Invalid IPv4 address in RTA_GATEWAY");
+					return -EINVAL;
+				}

Isn't the problem more general than that? It seems that there is no
minimum length validation to any of the attributes inside RTA_MULTIPATH.
Except maybe RTA_VIA

 				fib_cfg.fc_gw4 = nla_get_in_addr(nla);
 				if (fib_cfg.fc_gw4)
 					fib_cfg.fc_gw_family = AF_INET;
-- 
2.24.3 (Apple Git-128)

Re: [PATCH net] ipv4: Check attribute length for RTA_GATEWAY

From: David Ahern <hidden>
Date: 2021-12-11 22:13:05

On 12/11/21 12:13 PM, Ido Schimmel wrote:

On Sat, Dec 11, 2021 at 09:21:48AM -0700, David Ahern wrote:

quoted

syzbot reported uninit-value:
============================================================
  BUG: KMSAN: uninit-value in fib_get_nhs+0xac4/0x1f80
  net/ipv4/fib_semantics.c:708
   fib_get_nhs+0xac4/0x1f80 net/ipv4/fib_semantics.c:708
   fib_create_info+0x2411/0x4870 net/ipv4/fib_semantics.c:1453
   fib_table_insert+0x45c/0x3a10 net/ipv4/fib_trie.c:1224
   inet_rtm_newroute+0x289/0x420 net/ipv4/fib_frontend.c:886

Add length checking before using the attribute.

Fixes: 4e902c57417c ("[IPv4]: FIB configuration using struct fib_config")
Reported-by: syzbot+d4b9a2851cc3ce998741@syzkaller.appspotmail.com
Signed-off-by: David Ahern <dsahern@kernel.org>
Cc: Thomas Graf <tgraf@suug.ch>
---
I do not have KMSAN setup, so this is based on a code analysis. Before

Was using this in the past:
https://github.com/google/syzkaller/blob/master/docs/syzbot.md#kmsan-bugs

thanks for the pointer. I am a bit hardware challenged at the moment for
out of tree features.

quoted

4e902c57417c fib_get_attr32 was checking the attribute length; the
switch to nla_get_u32 does not.

 net/ipv4/fib_semantics.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/net/ipv4/fib_semantics.c b/net/ipv4/fib_semantics.c
index 3cad543dc747..930843ba3b17 100644
--- a/net/ipv4/fib_semantics.c
+++ b/net/ipv4/fib_semantics.c

@@ -704,6 +704,10 @@ static int fib_get_nhs(struct fib_info *fi, struct rtnexthop *rtnh,
 				return -EINVAL;
 			}
 			if (nla) {
+				if (nla_len(nla) < sizeof(__be32)) {
+					NL_SET_ERR_MSG(extack, "Invalid IPv4 address in RTA_GATEWAY");
+					return -EINVAL;
+				}

Isn't the problem more general than that? It seems that there is no
minimum length validation to any of the attributes inside RTA_MULTIPATH.
Except maybe RTA_VIA

A follow up commit is needed for RTA_FLOW.

Re: [PATCH net] ipv4: Check attribute length for RTA_GATEWAY

From: Ido Schimmel <hidden>
Date: 2021-12-12 08:09:27

On Sat, Dec 11, 2021 at 03:13:02PM -0700, David Ahern wrote:

On 12/11/21 12:13 PM, Ido Schimmel wrote:

quoted

On Sat, Dec 11, 2021 at 09:21:48AM -0700, David Ahern wrote:

quoted

syzbot reported uninit-value:
============================================================
  BUG: KMSAN: uninit-value in fib_get_nhs+0xac4/0x1f80
  net/ipv4/fib_semantics.c:708
   fib_get_nhs+0xac4/0x1f80 net/ipv4/fib_semantics.c:708
   fib_create_info+0x2411/0x4870 net/ipv4/fib_semantics.c:1453
   fib_table_insert+0x45c/0x3a10 net/ipv4/fib_trie.c:1224
   inet_rtm_newroute+0x289/0x420 net/ipv4/fib_frontend.c:886

Add length checking before using the attribute.

Fixes: 4e902c57417c ("[IPv4]: FIB configuration using struct fib_config")
Reported-by: syzbot+d4b9a2851cc3ce998741@syzkaller.appspotmail.com
Signed-off-by: David Ahern <dsahern@kernel.org>
Cc: Thomas Graf <tgraf@suug.ch>
---
I do not have KMSAN setup, so this is based on a code analysis. Before

Was using this in the past:
https://github.com/google/syzkaller/blob/master/docs/syzbot.md#kmsan-bugs

thanks for the pointer. I am a bit hardware challenged at the moment for
out of tree features.

quoted

4e902c57417c fib_get_attr32 was checking the attribute length; the
switch to nla_get_u32 does not.

 net/ipv4/fib_semantics.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/net/ipv4/fib_semantics.c b/net/ipv4/fib_semantics.c
index 3cad543dc747..930843ba3b17 100644
--- a/net/ipv4/fib_semantics.c
+++ b/net/ipv4/fib_semantics.c

@@ -704,6 +704,10 @@ static int fib_get_nhs(struct fib_info *fi, struct rtnexthop *rtnh,
 				return -EINVAL;
 			}
 			if (nla) {
+				if (nla_len(nla) < sizeof(__be32)) {
+					NL_SET_ERR_MSG(extack, "Invalid IPv4 address in RTA_GATEWAY");
+					return -EINVAL;
+				}

Isn't the problem more general than that? It seems that there is no
minimum length validation to any of the attributes inside RTA_MULTIPATH.
Except maybe RTA_VIA

A follow up commit is needed for RTA_FLOW.

The same problem seems to exists in the delete path and IPv6. See
fib_nh_match() and ip6_route_multipath_add(), for example.

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