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authorDavid Herrmann <dh.herrmann@gmail.com>2017-06-21 10:47:15 +0200
committerDavid S. Miller <davem@davemloft.net>2017-06-21 11:38:41 -0400
commit28b5ba2aa0f55d80adb2624564ed2b170c19519e (patch)
tree5598a2b2f8547ef0abc7a14efd9dcea823e8d8e6 /arch/m32r/include
parentudp: prefetch rmem_alloc in udp_queue_rcv_skb() (diff)
downloadlinux-dev-28b5ba2aa0f55d80adb2624564ed2b170c19519e.tar.xz
linux-dev-28b5ba2aa0f55d80adb2624564ed2b170c19519e.zip
net: introduce SO_PEERGROUPS getsockopt
This adds the new getsockopt(2) option SO_PEERGROUPS on SOL_SOCKET to retrieve the auxiliary groups of the remote peer. It is designed to naturally extend SO_PEERCRED. That is, the underlying data is from the same credentials. Regarding its syntax, it is based on SO_PEERSEC. That is, if the provided buffer is too small, ERANGE is returned and @optlen is updated. Otherwise, the information is copied, @optlen is set to the actual size, and 0 is returned. While SO_PEERCRED (and thus `struct ucred') already returns the primary group, it lacks the auxiliary group vector. However, nearly all access controls (including kernel side VFS and SYSVIPC, but also user-space polkit, DBus, ...) consider the entire set of groups, rather than just the primary group. But this is currently not possible with pure SO_PEERCRED. Instead, user-space has to work around this and query the system database for the auxiliary groups of a UID retrieved via SO_PEERCRED. Unfortunately, there is no race-free way to query the auxiliary groups of the PID/UID retrieved via SO_PEERCRED. Hence, the current user-space solution is to use getgrouplist(3p), which itself falls back to NSS and whatever is configured in nsswitch.conf(3). This effectively checks which groups we *would* assign to the user if it logged in *now*. On normal systems it is as easy as reading /etc/group, but with NSS it can resort to quering network databases (eg., LDAP), using IPC or network communication. Long story short: Whenever we want to use auxiliary groups for access checks on IPC, we need further IPC to talk to the user/group databases, rather than just relying on SO_PEERCRED and the incoming socket. This is unfortunate, and might even result in dead-locks if the database query uses the same IPC as the original request. So far, those recursions / dead-locks have been avoided by using primitive IPC for all crucial NSS modules. However, we want to avoid re-inventing the wheel for each NSS module that might be involved in user/group queries. Hence, we would preferably make DBus (and other IPC that supports access-management based on groups) work without resorting to the user/group database. This new SO_PEERGROUPS ioctl would allow us to make dbus-daemon work without ever calling into NSS. Cc: Michal Sekletar <msekleta@redhat.com> Cc: Simon McVittie <simon.mcvittie@collabora.co.uk> Reviewed-by: Tom Gundersen <teg@jklm.no> Signed-off-by: David Herrmann <dh.herrmann@gmail.com> Signed-off-by: David S. Miller <davem@davemloft.net>
Diffstat (limited to 'arch/m32r/include')
-rw-r--r--arch/m32r/include/uapi/asm/socket.h2
1 files changed, 2 insertions, 0 deletions
diff --git a/arch/m32r/include/uapi/asm/socket.h b/arch/m32r/include/uapi/asm/socket.h
index 5d97890a8704..f8f7b47e247f 100644
--- a/arch/m32r/include/uapi/asm/socket.h
+++ b/arch/m32r/include/uapi/asm/socket.h
@@ -100,4 +100,6 @@
#define SCM_TIMESTAMPING_PKTINFO 58
+#define SO_PEERGROUPS 59
+
#endif /* _ASM_M32R_SOCKET_H */