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manager: be stricter with incomining notifications, warn properly about too large ones

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Let's make the kernel let us know the full, original datagram size of the
incoming message. If it's larger than the buffer space provided by us, drop the
whole message with a warning.

Before this change the kernel would truncate the message for us to the buffer
space provided, and we'd not complain about this, and simply process the
incomplete message as far as it made sense.
This commit is contained in:
Lennart Poettering 2016-10-07 12:12:10 +02:00
parent c55ae51e77
commit 045a3d5989
1 changed files with 2 additions and 2 deletions
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4
src/core/manager.c
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@ -1720,7 +1720,7 @@ static int manager_dispatch_notify_fd(sd_event_source *source, int fd, uint32_t
return 0; return 0;
} }
n = recvmsg(m->notify_fd, &msghdr, MSG_DONTWAIT|MSG_CMSG_CLOEXEC); n = recvmsg(m->notify_fd, &msghdr, MSG_DONTWAIT|MSG_CMSG_CLOEXEC|MSG_TRUNC);
if (n < 0) { if (n < 0) {
if (IN_SET(errno, EAGAIN, EINTR)) if (IN_SET(errno, EAGAIN, EINTR))
return 0; /* Spurious wakeup, try again */ return 0; /* Spurious wakeup, try again */
@ -1761,7 +1761,7 @@ static int manager_dispatch_notify_fd(sd_event_source *source, int fd, uint32_t
return 0; return 0;
} }
if ((size_t) n >= sizeof(buf)) { if ((size_t) n >= sizeof(buf) || (msghdr.msg_flags & MSG_TRUNC)) {
log_warning("Received notify message exceeded maximum size. Ignoring."); log_warning("Received notify message exceeded maximum size. Ignoring.");
return 0; return 0;
} }