6.5-stable review patch. If anyone has any objections, please let me know.
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From: Kuniyuki Iwashima kuniyu@amazon.com
[ Upstream commit 718e6b51298e0f254baca0d40ab52a00e004e014 ]
Heiko Carstens reported that SCM_PIDFD does not work with MSG_CMSG_COMPAT because scm_pidfd_recv() always checks msg_controllen against sizeof(struct cmsghdr).
We need to use sizeof(struct compat_cmsghdr) for the compat case.
Fixes: 5e2ff6704a27 ("scm: add SO_PASSPIDFD and SCM_PIDFD") Reported-by: Heiko Carstens hca@linux.ibm.com Closes: https://lore.kernel.org/netdev/20230901200517.8742-A-hca@linux.ibm.com/ Signed-off-by: Kuniyuki Iwashima kuniyu@amazon.com Tested-by: Heiko Carstens hca@linux.ibm.com Reviewed-by: Alexander Mikhalitsyn aleksandr.mikhalitsyn@canonical.com Reviewed-by: Michal Swiatkowski michal.swiatkowski@linux.intel.com Acked-by: Christian Brauner brauner@kernel.org Signed-off-by: David S. Miller davem@davemloft.net Signed-off-by: Sasha Levin sashal@kernel.org --- include/net/scm.h | 14 +++++++++----- 1 file changed, 9 insertions(+), 5 deletions(-)
diff --git a/include/net/scm.h b/include/net/scm.h index c5bcdf65f55c9..e8c76b4be2fe7 100644 --- a/include/net/scm.h +++ b/include/net/scm.h @@ -9,6 +9,7 @@ #include <linux/pid.h> #include <linux/nsproxy.h> #include <linux/sched/signal.h> +#include <net/compat.h>
/* Well, we should have at least one descriptor open * to accept passed FDs 8) @@ -123,14 +124,17 @@ static inline bool scm_has_secdata(struct socket *sock) static __inline__ void scm_pidfd_recv(struct msghdr *msg, struct scm_cookie *scm) { struct file *pidfd_file = NULL; - int pidfd; + int len, pidfd;
- /* - * put_cmsg() doesn't return an error if CMSG is truncated, + /* put_cmsg() doesn't return an error if CMSG is truncated, * that's why we need to opencode these checks here. */ - if ((msg->msg_controllen <= sizeof(struct cmsghdr)) || - (msg->msg_controllen - sizeof(struct cmsghdr)) < sizeof(int)) { + if (msg->msg_flags & MSG_CMSG_COMPAT) + len = sizeof(struct compat_cmsghdr) + sizeof(int); + else + len = sizeof(struct cmsghdr) + sizeof(int); + + if (msg->msg_controllen < len) { msg->msg_flags |= MSG_CTRUNC; return; }