[PATCH net] xfrm: fix integer overflow in xfrm_replay_state_esn_len()

Dan Carpenter
2025-01-21T11:16:06Z

The problem is that "replay_esn->bmp_len" comes from the user and it's
a u32. The xfrm_replay_state_esn_len() function also returns a u32.
So if we choose a ->bmp_len which very high then the total will be
more than UINT_MAX and value will be truncated when we return. The
returned value will be smaller than expected causing problems in the
caller.

To fix this:
1) Use size_add() and size_mul(). This change is necessary for 32bit
systems.
2) Change the type of xfrm_replay_state_esn_len() and related variables
from u32 to size_t.
3) Remove the casts to (int). The size should never be negative.
Generally, values which come from size_add/mul() should stay as type
size_t and not be truncated to user fewer than all the bytes in a
unsigned long.

Cc: stable@vger.kernel.org
Fixes: 9736acf395d3 ("xfrm: Add basic infrastructure to support IPsec extended sequence numbers")
Signed-off-by: Dan Carpenter <dan.carpenter@linaro.org>
---
The one caller that I didn't modify was xfrm_sa_len(). That's a bit
complicated and also I'm kind of hoping that we don't handle user
controlled data in that function? The place where we definitely are
handling user data is in xfrm_alloc_replay_state_esn() and this patch
fixes that.

include/net/xfrm.h | 4 ++--
net/xfrm/xfrm_user.c | 10 +++++-----
2 files changed, 7 insertions(+), 7 deletions(-)

diff --git a/include/net/xfrm.h b/include/net/xfrm.h
index ed4b83696c77..0a42614d7840 100644
--- a/include/net/xfrm.h
+++ b/include/net/xfrm.h
@@ -1981,9 +1981,9 @@ static inline unsigned int xfrm_alg_auth_len(const struct xfrm_algo_auth *alg)
return sizeof(*alg) + ((alg->alg_key_len + 7) / 8);
}

-static inline unsigned int xfrm_replay_state_esn_len(struct xfrm_replay_state_esn *replay_esn)
+static inline size_t xfrm_replay_state_esn_len(struct xfrm_replay_state_esn *replay_esn)
{
- return sizeof(*replay_esn) + replay_esn->bmp_len * sizeof(__u32);
+ return size_add(sizeof(*replay_esn), size_mul(replay_esn->bmp_len, sizeof(__u32)));
}

#ifdef CONFIG_XFRM_MIGRATE
diff --git a/net/xfrm/xfrm_user.c b/net/xfrm/xfrm_user.c
index 08c6d6f0179f..4bfa72547dab 100644
--- a/net/xfrm/xfrm_user.c
+++ b/net/xfrm/xfrm_user.c
@@ -151,7 +151,7 @@ static inline int verify_replay(struct xfrm_usersa_info *p,
return -EINVAL;
}

- if (nla_len(rt) < (int)xfrm_replay_state_esn_len(rs) &&
+ if (nla_len(rt) < xfrm_replay_state_esn_len(rs) &&
nla_len(rt) != sizeof(*rs)) {
NL_SET_ERR_MSG(extack, "ESN attribute is too short to fit the full bitmap length");
return -EINVAL;
@@ -681,7 +681,7 @@ static inline int xfrm_replay_verify_len(struct xfrm_replay_state_esn *replay_es
struct netlink_ext_ack *extack)
{
struct xfrm_replay_state_esn *up;
- unsigned int ulen;
+ size_t ulen;

if (!replay_esn || !rp)
return 0;
@@ -691,7 +691,7 @@ static inline int xfrm_replay_verify_len(struct xfrm_replay_state_esn *replay_es

/* Check the overall length and the internal bitmap length to avoid
* potential overflow. */
- if (nla_len(rp) < (int)ulen) {
+ if (nla_len(rp) < ulen) {
NL_SET_ERR_MSG(extack, "ESN attribute is too short");
return -EINVAL;
}
@@ -719,14 +719,14 @@ static int xfrm_alloc_replay_state_esn(struct xfrm_replay_state_esn **replay_esn
struct nlattr *rta)
{
struct xfrm_replay_state_esn *p, *pp, *up;
- unsigned int klen, ulen;
+ size_t klen, ulen;

if (!rta)
return 0;

up = nla_data(rta);
klen = xfrm_replay_state_esn_len(up);
- ulen = nla_len(rta) >= (int)klen ? klen : sizeof(*up);
+ ulen = nla_len(rta) >= klen ? klen : sizeof(*up);

p = kzalloc(klen, GFP_KERNEL);
if (!p)
--
2.45.2