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tree-wide: ignore messages with too long control data

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Apparently SELinux inserts control data into AF_UNIX datagrams where we
don't expect it, thus miscalculating the control data. This looks like
something to fix in SELinux, but we still should handle this gracefully
and just drop the offending datagram and continue.

recvmsg_safe() actually already drops the datagram, it's just a matter
of actually ignoring EXFULL (which it generates if control data is too
large) in the right places.

This does this wherever an AF_UNIX/SOCK_DGRAM socket is used with
recvmsg_safe() that is not just internal communication.

Fixes: #17795
Follow-up for: 3691bcf3c5eebdcca5b4f1c51c745441c57a6cd1

(cherry picked from commit 741bfd7f4e60fdc07ecaadbd93f1196dbee657ca)
(cherry picked from commit b7e0ac754eba3c91b76dc7b92802716144b569b8)
This commit is contained in:
Lennart Poettering 2021-01-19 21:34:20 +01:00 committed by Zbigniew Jędrzejewski-Szmek
parent f3a4ccbcca
commit f96df55cd8
3 changed files with 12 additions and 0 deletions
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4
src/core/manager.c
View File

@ -2389,6 +2389,10 @@ static int manager_dispatch_notify_fd(sd_event_source *source, int fd, uint32_t
n = recvmsg_safe(m->notify_fd, &msghdr, MSG_DONTWAIT|MSG_CMSG_CLOEXEC|MSG_TRUNC);
if (IN_SET(n, -EAGAIN, -EINTR))
return 0; /* Spurious wakeup, try again */
if (n == -EXFULL) {
log_warning("Got message with truncated control data (too many fds sent?), ignoring.");
return 0;
}
if (n < 0)
/* If this is any other, real error, then let's stop processing this socket. This of course
* means we won't take notification messages anymore, but that's still better than busy

4
src/nspawn/nspawn.c
View File

@ -3772,6 +3772,10 @@ static int nspawn_dispatch_notify_fd(sd_event_source *source, int fd, uint32_t r
n = recvmsg_safe(fd, &msghdr, MSG_DONTWAIT|MSG_CMSG_CLOEXEC);
if (IN_SET(n, -EAGAIN, -EINTR))
return 0;
if (n == -EXFULL) {
log_warning("Got message with truncated control data (too many fds sent?), ignoring.");
return 0;
}
if (n < 0)
return log_warning_errno(n, "Couldn't read notification socket: %m");

4
src/shared/ask-password-api.c
View File

@ -946,6 +946,10 @@ int ask_password_agent(
n = recvmsg_safe(socket_fd, &msghdr, 0);
if (IN_SET(n, -EAGAIN, -EINTR))
continue;
if (n == -EXFULL) {
log_debug("Got message with truncated control data, ignoring.");
continue;
}
if (n < 0) {
r = (int) n;
goto finish;