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net/iucv: fix locking in .getsockopt

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Mirror iucv_sock_setsockopt() and wrap the whole switch in
lock_sock()/release_sock(). The pre-existing SO_MSGLIMIT-only lock
becomes redundant and is removed.

Any AF_IUCV HIPER user can potentially crash the kernel by racing
recvmsg() with getsockopt(SO_MSGSIZE): the SO_MSGSIZE arm dereferences
iucv->hs_dev->mtu after iucv_sock_close() (called from the racing
recvmsg()) has set hs_dev to NULL, producing a NULL pointer dereference
oops.

Suggested-by: Stanislav Fomichev <sdf.kernel@gmail.com>
Fixes: 51363b8751 ("af_iucv: allow retrieval of maximum message size")
Signed-off-by: Breno Leitao <leitao@debian.org>
Reviewed-by: Alexandra Winter <wintera@linux.ibm.com>
Tested-by: Alexandra Winter <wintera@linux.ibm.com>
Link: https://patch.msgid.link/20260521-af_iucv_fix2-v1-1-f16b1c510aa9@debian.org
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
This commit is contained in:
Breno Leitao
2026-05-21 07:11:45 -07:00
committed by Jakub Kicinski
parent 9e4389b003
commit 3589d20a66
1 changed files with 14 additions and 6 deletions
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20
net/iucv/af_iucv.c
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@@ -1540,7 +1540,7 @@ static int iucv_sock_getsockopt(struct socket *sock, int level, int optname,
struct sock *sk = sock->sk;
struct iucv_sock *iucv = iucv_sk(sk);
unsigned int val;
int len;
int len, rc;
if (level != SOL_IUCV)
return -ENOPROTOOPT;
@@ -1553,26 +1553,34 @@ static int iucv_sock_getsockopt(struct socket *sock, int level, int optname,
len = min_t(unsigned int, len, sizeof(int));
rc = 0;
lock_sock(sk);
switch (optname) {
case SO_IPRMDATA_MSG:
val = (iucv->flags & IUCV_IPRMDATA) ? 1 : 0;
break;
case SO_MSGLIMIT:
lock_sock(sk);
val = (iucv->path != NULL) ? iucv->path->msglim /* connected */
: iucv->msglimit; /* default */
release_sock(sk);
break;
case SO_MSGSIZE:
if (sk->sk_state == IUCV_OPEN)
return -EBADFD;
if (sk->sk_state == IUCV_OPEN) {
rc = -EBADFD;
break;
}
val = (iucv->hs_dev) ? iucv->hs_dev->mtu -
sizeof(struct af_iucv_trans_hdr) - ETH_HLEN :
0x7fffffff;
break;
default:
return -ENOPROTOOPT;
rc = -ENOPROTOOPT;
break;
}
release_sock(sk);
if (rc)
return rc;
if (put_user(len, optlen))
return -EFAULT;