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Introduced in commit f37708f6b8 (2.10). The NBD spec says a client
can request export names up to 4096 bytes in length, even though
they should not expect success on names longer than 256. However,
qemu hard-codes the limit of 256, and fails to filter out a client
that probes for a longer name; the result is a stack smash that can
potentially give an attacker arbitrary control over the qemu
process.
The smash can be easily demonstrated with this client:
$ qemu-io f raw nbd://localhost:10809/$(printf %3000d 1 | tr ' ' a)
If the qemu NBD server binary (whether the standalone qemu-nbd, or
the builtin server of QMP nbd-server-start) was compiled with
-fstack-protector-strong, the ability to exploit the stack smash
into arbitrary execution is a lot more difficult (but still
theoretically possible to a determined attacker, perhaps in
combination with other CVEs). Still, crashing a running qemu (and
losing the VM) is bad enough, even if the attacker did not obtain
full execution control.
CC: qemu-stable@nongnu.org
Signed-off-by: Eric Blake <eblake@redhat.com>
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The NBD spec gives us permission to abruptly disconnect on clients
that send outrageously large option requests, rather than having
to spend the time reading to the end of the option. No real
option request requires that much data anyways; and meanwhile, we
already have the practice of abruptly dropping the connection on
any client that sends NBD_CMD_WRITE with a payload larger than 32M.
For comparison, nbdkit drops the connection on any request with
more than 4096 bytes; however, that limit is probably too low
(as the NBD spec states an export name can theoretically be up
to 4096 bytes, which means a valid NBD_OPT_INFO could be even
longer) - even if qemu doesn't permit exports longer than 256
bytes.
It could be argued that a malicious client trying to get us to
read nearly 4G of data on a bad request is a form of denial of
service. In particular, if the server requires TLS, but a client
that does not know the TLS credentials sends any option (other
than NBD_OPT_STARTTLS or NBD_OPT_EXPORT_NAME) with a stated
payload of nearly 4G, then the server was keeping the connection
alive trying to read all the payload, tying up resources that it
would rather be spending on a client that can get past the TLS
handshake. Hence, this warranted a CVE.
Present since at least 2.5 when handling known options, and made
worse in 2.6 when fixing support for NBD_FLAG_C_FIXED_NEWSTYLE
to handle unknown options.
CC: qemu-stable@nongnu.org
Signed-off-by: Eric Blake <eblake@redhat.com>
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The NBD spec says an attempt to NBD_CMD_TRIM on a read-only
export should fail with EPERM, as a trim has the potential
to change disk contents, but we were relying on the block
layer to catch that for us, which might not always give the
right error (and even if it does, it does not let us pass
back a sane message for structured replies).
The NBD spec says an attempt to NBD_CMD_WRITE_ZEROES out of
bounds should fail with ENOSPC, not EINVAL.
Our check for u64 offset + u32 length wraparound up front is
pointless; nothing uses offset until after the second round
of sanity checks, and we can just as easily ensure there is
no wraparound by checking whether offset is in bounds (since
a disk size cannot exceed off_t which is 63 bits, adding a
32-bit number for a valid offset can't overflow). Bonus:
dropping the up-front check lets us keep the connection alive
after NBD_CMD_WRITE, whereas before we would drop the
connection (of course, any client sending a packet that would
trigger the failure is already buggy, so it's also okay to
drop the connection, but better quality-of-implementation
never hurts).
Solve all of these issues by some code motion and improved
request validation.
Signed-off-by: Eric Blake <eblake@redhat.com>
Message-Id: <20171115213557.3548-1-eblake@redhat.com>
Reviewed-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
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The NBD spec was recently clarified to state that a read of length 0
should not be attempted by a compliant client; but that a server must
still handle it correctly in an unspecified manner (that is, either
a successful no-op or an error reply, but not a crash) [1]. However,
it also implies that NBD_REPLY_TYPE_OFFSET_DATA must have a non-zero
payload length, but our existing code was replying with a chunk
that a picky client could reject as invalid because it was missing
a payload (our own client implementation was recently patched to be
that picky, after first fixing it to not send 0-length requests).
We are already doing successful no-ops for 0-length writes and for
non-structured reads; so for consistency, we want structured reply
reads to also be a no-op. The easiest way to do this is to return
a NBD_REPLY_TYPE_NONE chunk; this is best done via a new helper
function (especially since future patches for other structured
replies may benefit from using the same helper).
[1] https://github.com/NetworkBlockDevice/nbd/commit/ee926037
Signed-off-by: Eric Blake <eblake@redhat.com>
Message-Id: <20171108215703.9295-8-eblake@redhat.com>
Reviewed-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
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A closer read of the NBD spec shows that a structured reply chunk
for a hole is not quite identical to the prefix of a data chunk,
because the hole has to also send a 32-bit size field. Although
we do not yet send holes, we should fix the misleading information
in our header and make it easier for a future patch to support
sparse reads. Messed up in commit bae245d1.
Signed-off-by: Eric Blake <eblake@redhat.com>
Message-Id: <20171108215703.9295-5-eblake@redhat.com>
Reviewed-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
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namelen should be here, length is unrelated, and always 0 at this
point. Broken in introduction in commit f37708f6, but mostly
harmless (replying with '' as the name does not violate protocol,
and does not confuse qemu as the nbd client since our implementation
does not ask for the name; but might confuse some other client that
does ask for the name especially if the default export is different
than the export name being queried).
Adding an assert makes it obvious that we are not skipping any bytes
in the client's message, as well as making it obvious that we were
using the wrong variable.
Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
CC: qemu-stable@nongnu.org
Message-Id: <20171101154204.27146-1-vsementsov@virtuozzo.com>
[eblake: improve commit message, squash in assert addition]
Signed-off-by: Eric Blake <eblake@redhat.com>
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The NBD spec permits including a human-readable error string if
structured replies are in force, so we might as well send the
client the message that we logged on any error.
Signed-off-by: Eric Blake <eblake@redhat.com>
Reviewed-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
Message-Id: <20171027104037.8319-9-eblake@redhat.com>
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Minimal implementation of structured read: one structured reply chunk,
no segmentation.
Minimal structured error implementation: no text message.
Support DF flag, but just ignore it, as there is no segmentation any
way.
Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
Signed-off-by: Eric Blake <eblake@redhat.com>
Message-Id: <20171027104037.8319-8-eblake@redhat.com>
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Consolidate the response for a non-zero-length option payload
into a new function, nbd_reject_length(). This check will
also be used when introducing support for structured replies.
Note that STARTTLS response differs based on time: if the connection
is still unencrypted, we set fatal to true (a client that can't
request TLS correctly may still think that we are ready to start
the TLS handshake, so we must disconnect); while if the connection
is already encrypted, the client is sending a bogus request but
is no longer at risk of being confused by continuing the connection.
Signed-off-by: Eric Blake <eblake@redhat.com>
Message-Id: <20171027104037.8319-7-eblake@redhat.com>
[eblake: correct return value on STARTTLS]
Reviewed-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
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Instead of making each caller check whether a transmission error
occurred, we can sink a common error check to the end of the loop.
Signed-off-by: Eric Blake <eblake@redhat.com>
Message-Id: <20171027104037.8319-6-eblake@redhat.com>
[eblake: squash in compiler warning fix]
Reviewed-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
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When the server is read-only, we were already reporting an error
message for NBD_CMD_WRITE_ZEROES, but failed to set errp for a
similar NBD_CMD_WRITE. This will matter more once structured
replies allow the server to propagate the errp information back
to the client. While at it, use an error message that makes a
bit more sense if viewed on the client side.
Note that when using qemu-io to test qemu-nbd behavior, it is
rather difficult to convince qemu-io to send protocol violations
(such as a read beyond bounds), because we have a lot of active
checking on the client side that a qemu-io request makes sense
before it ever goes over the wire to the server. The case of a
client attempting a write when the server is started as
'qemu-nbd -r' is one of the few places where we can easily test
error path handling, without having to resort to hacking in known
temporary bugs to either the server or client. [Maybe we want a
future patch to the client to do up-front checking on writes to a
read-only export, the way it does up-front bounds checking; but I
don't see anything in the NBD spec that points to a protocol
violation in our current behavior.]
Signed-off-by: Eric Blake <eblake@redhat.com>
Reviewed-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
Message-Id: <20171027104037.8319-5-eblake@redhat.com>
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Upcoming patches will implement the NBD structured reply
extension [1] for both client and server roles. Declare the
constants, structs, and lookup routines that will be valuable
whether the server or client code is backported in isolation.
This includes moving one constant from an internal header to
the public header, as part of the structured read processing
will be done in block/nbd-client.c rather than nbd/client.c.
[1]https://github.com/NetworkBlockDevice/nbd/blob/extension-structured-reply/doc/proto.md
Based on patches from Vladimir Sementsov-Ogievskiy.
Signed-off-by: Eric Blake <eblake@redhat.com>
Reviewed-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
Message-Id: <20171027104037.8319-4-eblake@redhat.com>
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NBD errors were originally sent over the wire based on Linux errno
values; but not all the world is Linux, and not all platforms share
the same values. Since a number isn't very easy to decipher on all
platforms, update the trace messages to include the name of NBD
errors being sent/received over the wire. Tweak the trace messages
to be at the point where we are using the NBD error, not the
translation to the host errno values.
Signed-off-by: Eric Blake <eblake@redhat.com>
Reviewed-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
Message-Id: <20171027104037.8319-2-eblake@redhat.com>
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Send qiov via qio_channel_writev_all instead of calling nbd_write twice
with a cork.
Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
Message-Id: <20171012095319.136610-8-vsementsov@virtuozzo.com>
[eblake: rebase to tweaks earlier in series]
Signed-off-by: Eric Blake <eblake@redhat.com>
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Pass client and buffer (*data) parameters directly, to make the function
consistent with further structured reply sending functions.
Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
Message-Id: <20171012095319.136610-7-vsementsov@virtuozzo.com>
Signed-off-by: Eric Blake <eblake@redhat.com>
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NBDReply structure will be upgraded in future patches to handle both
simple and structured replies and will be used only in the client
Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
Message-Id: <20171012095319.136610-6-vsementsov@virtuozzo.com>
[eblake: rebase to tweaks earlier in series]
Signed-off-by: Eric Blake <eblake@redhat.com>
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Use packed structure instead of pointer arithmetics.
Also, merge two redundant traces into one.
Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
Message-Id: <20171012095319.136610-5-vsementsov@virtuozzo.com>
[eblake: tweak and mention impact on traces, fix errp usage]
Signed-off-by: Eric Blake <eblake@redhat.com>
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To be consistent when their _structured_ analogs will be introduced.
Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
Message-Id: <20171012095319.136610-4-vsementsov@virtuozzo.com>
[eblake: also tweak trace message contents]
Signed-off-by: Eric Blake <eblake@redhat.com>
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Signed-off-by: Marc-André Lureau <marcandre.lureau@redhat.com>
Message-Id: <20171006235023.11952-22-f4bug@amsat.org>
Signed-off-by: Eric Blake <eblake@redhat.com>
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The "inactive" state of BDS affects whether the permissions can be
granted, we must call bdrv_invalidate_cache before bdrv_set_perm to
support "-incoming defer" case.
Reported-by: Christian Ehrhardt <christian.ehrhardt@canonical.com>
Signed-off-by: Fam Zheng <famz@redhat.com>
Message-Id: <20170815130740.31229-3-famz@redhat.com>
Signed-off-by: Eric Blake <eblake@redhat.com>
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A typo in commit 23e099c set the size of buf[] used in response
to NBD_OPT_EXPORT_NAME according to the length needed for old-style
negotiation (4 bytes of flag information) instead of the intended
2 bytes used in new style. If the client doesn't enable
NBD_FLAG_C_NO_ZEROES, then the server sends two bytes too many,
and is then out of sync in response to the client's next command
(the bug is masked when modern qemu is the client, since we enable
the no zeroes flag).
While touching this code, add some more defines to nbd_internal.h
rather than having quite so many magic numbers in the .c; also,
use "" initialization rather than memset(), and tweak the oldstyle
negotiation to better match the spec description of the layout
(since the spec is big-endian, skipping two bytes as 0 followed by
writing a 2-byte flag is the same as writing a zero-extended 4-byte
flag), to make it a bit easier to follow compared to the spec.
[checkpatch.pl has some false positives in the comments]
Signed-off-by: Eric Blake <eblake@redhat.com>
Message-Id: <20170717192635.17880-3-eblake@redhat.com>
Reviewed-by: John Snow <jsnow@redhat.com>
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The upstream NBD Protocol has defined a new extension to allow
the server to advertise block sizes to the client, as well as
a way for the client to inform the server that it intends to
obey block sizes.
Thanks to a recent fix (commit df7b97ff), our real minimum
transfer size is always 1 (the block layer takes care of
read-modify-write on our behalf), but we're still more efficient
if we advertise 512 when the client supports it, as follows:
- OPT_INFO, but no NBD_INFO_BLOCK_SIZE: advertise 512, then
fail with NBD_REP_ERR_BLOCK_SIZE_REQD; client is free to try
something else since we don't disconnect
- OPT_INFO with NBD_INFO_BLOCK_SIZE: advertise 512
- OPT_GO, but no NBD_INFO_BLOCK_SIZE: advertise 1
- OPT_GO with NBD_INFO_BLOCK_SIZE: advertise 512
We can also advertise the optimum block size (presumably the
cluster size, when exporting a qcow2 file), and our absolute
maximum transfer size of 32M, to help newer clients avoid
EINVAL failures or abrupt disconnects on oversize requests.
We do not reject clients for using the older NBD_OPT_EXPORT_NAME;
we are no worse off for those clients than we used to be.
Signed-off-by: Eric Blake <eblake@redhat.com>
Message-Id: <20170707203049.534-9-eblake@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
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NBD_OPT_EXPORT_NAME is lousy: per the NBD protocol, any failure
requires us to close the connection rather than report an error.
Therefore, upstream NBD recently added NBD_OPT_GO as the improved
version of the option that does what we want [1], along with
NBD_OPT_INFO that returns the same information but does not
transition to transmission phase.
[1] https://github.com/NetworkBlockDevice/nbd/blob/extension-info/doc/proto.md
This is a first cut at the information types, and only passes the
same information already available through NBD_OPT_LIST and
NBD_OPT_EXPORT_NAME; items like NBD_INFO_BLOCK_SIZE (and thus any
use of NBD_REP_ERR_BLOCK_SIZE_REQD) are intentionally left for
later patches.
Signed-off-by: Eric Blake <eblake@redhat.com>
Message-Id: <20170707203049.534-7-eblake@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
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Reply directly in nbd_negotiate_handle_export_name(), rather than
waiting until nbd_negotiate_options() completes. This will make it
easier to implement NBD_OPT_GO. Pass additional parameters around,
rather than stashing things inside NBDClient.
Signed-off-by: Eric Blake <eblake@redhat.com>
Message-Id: <20170707203049.534-6-eblake@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
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Simplify the tracing of client flags in the server, and return -EINVAL
instead of -EIO if we successfully read but don't like those flags.
Signed-off-by: Eric Blake <eblake@redhat.com>
Message-Id: <20170707203049.534-5-eblake@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
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The NBD protocol has several constants defined in various extensions
that we are about to implement. Expose them to the code, along with
an easy way to map various constants to strings during diagnostic
messages.
Signed-off-by: Eric Blake <eblake@redhat.com>
Message-Id: <20170707203049.534-4-eblake@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
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We really don't care if our spec-compliant reply to NBD_OPT_ABORT
was received, so shave off some lines of code by not even tracing it.
Signed-off-by: Eric Blake <eblake@redhat.com>
Message-Id: <20170707203049.534-3-eblake@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
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Let NBD use the trace mechanisms already present in qemu. Now you can
use the -trace optino of qemu, or the -T/--trace option of qemu-img,
qemu-io, and qemu-nbd, to select nbd traces. For qemu, the QMP commands
trace-event-{get,set}-state can also toggle tracing on the fly.
Example:
qemu-nbd --trace 'nbd_*' <image file> # enables all nbd traces
Recompilation with CFLAGS=-DDEBUG_NBD is no more needed, furthermore,
DEBUG_NBD macro is removed from the code.
Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
Message-Id: <20170707152918.23086-11-vsementsov@virtuozzo.com>
[eblake: minor tweaks to a couple of traces]
Signed-off-by: Eric Blake <eblake@redhat.com>
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Reorganize traces: move, reword, add information, drop extra ones.
Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
Message-Id: <20170707152918.23086-10-vsementsov@virtuozzo.com>
Signed-off-by: Eric Blake <eblake@redhat.com>
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Rename 'clientflags' to just 'option'. This variable has nothing to do
with flags, but is a single integer representing the option requested
by the client.
Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
Message-Id: <20170707152918.23086-9-vsementsov@virtuozzo.com>
Signed-off-by: Eric Blake <eblake@redhat.com>
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Fix wrong order of TRACE arguments.
Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
Message-Id: <20170707152918.23086-8-vsementsov@virtuozzo.com>
Signed-off-by: Eric Blake <eblake@redhat.com>
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Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
Message-Id: <20170707152918.23086-5-vsementsov@virtuozzo.com>
Signed-off-by: Eric Blake <eblake@redhat.com>
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Move to modern errp scheme from just LOGging errors.
Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
Message-Id: <20170707152918.23086-4-vsementsov@virtuozzo.com>
Signed-off-by: Eric Blake <eblake@redhat.com>
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Combine two successive "if (oldStyle) {...} else {...}" into one.
Block "if (client->tlscreds)" under "if (oldStyle)" is unreachable,
as we have "oldStyle = client->exp != NULL && !client->tlscreds;".
So, delete this block.
Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
Message-Id: <20170707152918.23086-3-vsementsov@virtuozzo.com>
Signed-off-by: Eric Blake <eblake@redhat.com>
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Separate the case when a client sends NBD_OPT_ABORT from all other
errors. It will be needed for the following patch, where errors will be
reported.
This particular case is not actually an error - it honestly follows the
NBD protocol. Therefore it should not be reported like an error.
Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
Message-Id: <20170707152918.23086-2-vsementsov@virtuozzo.com>
Signed-off-by: Eric Blake <eblake@redhat.com>
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- do not use 'goto error_reply' outside a switch to jump into the
middle of the switch's default case label
- reduce code duplication
Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
Message-Id: <20170602150150.258222-13-vsementsov@virtuozzo.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
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For consistency use 'ret' name for saving return code everywhere
in the file.
Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
Message-Id: <20170602150150.258222-12-vsementsov@virtuozzo.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
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"goto fail" error handling scheme is not needed for just returning
error code. Better is return it immediately.
Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
Message-Id: <20170602150150.258222-11-vsementsov@virtuozzo.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
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Current code will return 0 on this nbd_write fail, as rc is 0
after successful nbd_negotiate_options. Fix this.
Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
Message-Id: <20170602150150.258222-10-vsementsov@virtuozzo.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
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"co" field of NBDClientNewData has never been used, all the way back to
its declaration in commit 1a6245a5. So let's just use client pointer
instead of extra structure.
Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
Message-Id: <20170602150150.258222-9-vsementsov@virtuozzo.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
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Move function tail, about receiving next request out of the function.
Error path is simplified and nbd_co_receive_request becomes more
corresponding to its name.
Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
Message-Id: <20170602150150.258222-8-vsementsov@virtuozzo.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
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For now nbd_read never returns EAGAIN. So, don't handle it.
Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
Message-Id: <20170602150150.258222-7-vsementsov@virtuozzo.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
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As nbd_write never returns value > 0, we can get rid of extra ret.
Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
Message-Id: <20170602150150.258222-6-vsementsov@virtuozzo.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
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Now nbd_read and friends return int, so get rid of ssize_t.
Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
Message-Id: <20170602150150.258222-5-vsementsov@virtuozzo.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
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Functions nbd_negotiate_{read,write,drop_sync} were introduced in
1a6245a5b, when nbd_rwv (was nbd_wr_sync) was working through
qemu_co_sendv_recvv (the path is nbd_wr_sync -> qemu_co_{recv/send} ->
qemu_co_send_recv -> qemu_co_sendv_recvv), which just yields, without
setting any handlers. But starting from ff82911cd nbd_rwv (was
nbd_wr_syncv) works through qio_channel_yield() which sets handlers, so
watchers are redundant in nbd_negotiate_{read,write,drop_sync}, then,
let's just use nbd_{read,write,drop} functions.
Functions nbd_{read,write,drop} has errp parameter, which is unused in
this patch. This will be fixed later.
Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
Message-Id: <20170602150150.258222-4-vsementsov@virtuozzo.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
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Rename
nbd_wr_syncv -> nbd_rwv
read_sync -> nbd_read
read_sync_eof -> nbd_read_eof
write_sync -> nbd_write
drop_sync -> nbd_drop
1. nbd_ prefix
read_sync and write_sync are already shared, so it is good to have a
namespace prefix. drop_sync will be shared, and read_sync_eof is
related to read_sync, so let's rename them all.
2. _sync suffix
_sync is related to the fact that nbd_wr_syncv doesn't return if a
write to socket returns EAGAIN. The first implementation of
nbd_wr_syncv (was wr_sync in 7a5ca8648b) just loops while getting
EAGAIN, the current implementation yields in this case.
Why we want to get rid of it:
- it is normal for r/w functions to be synchronous, so having an
additional suffix for it looks redundant (contrariwise, we have
_aio suffix for async functions)
- _sync suffix in block layer is used when function does flush (so
using it for other thing is confusing a bit)
- keep function names short after adding nbd_ prefix
3. for nbd_wr_syncv let's use more common notation 'rw'
Reviewed-by: Eric Blake <eblake@redhat.com>
Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
Message-Id: <20170602150150.258222-2-vsementsov@virtuozzo.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
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Back in qemu 2.5, qemu-nbd was immune to port probes (a transient
server would not quit, regardless of how many probe connections
came and went, until a connection actually negotiated). But we
broke that in commit ee7d7aa when removing the return value to
nbd_client_new(), although that patch also introduced a bug causing
an assertion failure on a client that fails negotiation. We then
made it worse during refactoring in commit 1a6245a (a segfault
before we could even assert); the (masked) assertion was cleaned
up in d3780c2 (still in 2.6), and just recently we finally fixed
the segfault ("nbd: Fully intialize client in case of failed
negotiation"). But that still means that ever since we added
TLS support to qemu-nbd, we have been vulnerable to an ill-timed
port-scan being able to cause a denial of service by taking down
qemu-nbd before a real client has a chance to connect.
Since negotiation is now handled asynchronously via coroutines,
we no longer have a synchronous point of return by re-adding a
return value to nbd_client_new(). So this patch instead wires
things up to pass the negotiation status through the close_fn
callback function.
Simple test across two terminals:
$ qemu-nbd -f raw -p 30001 file
$ nmap 127.0.0.1 -p 30001 && \
qemu-io -c 'r 0 512' -f raw nbd://localhost:30001
Note that this patch does not change what constitutes successful
negotiation (thus, a client must enter transmission phase before
that client can be considered as a reason to terminate the server
when the connection ends). Perhaps we may want to tweak things
in a later patch to also treat a client that uses NBD_OPT_ABORT
as being a 'successful' negotiation (the client correctly talked
the NBD protocol, and informed us it was not going to use our
export after all), but that's a discussion for another day.
Fixes: https://bugzilla.redhat.com/show_bug.cgi?id=1451614
Signed-off-by: Eric Blake <eblake@redhat.com>
Message-Id: <20170608222617.20376-1-eblake@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
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If a non-NBD client connects to qemu-nbd, we would end up with
a SIGSEGV in nbd_client_put() because we were trying to
unregister the client's association to the export, even though
we skipped inserting the client into that list. Easy trigger
in two terminals:
$ qemu-nbd -p 30001 --format=raw file
$ nmap 127.0.0.1 -p 30001
nmap claims that it thinks it connected to a pago-services1
server (which probably means nmap could be updated to learn the
NBD protocol and give a more accurate diagnosis of the open
port - but that's not our problem), then terminates immediately,
so our call to nbd_negotiate() fails. The fix is to reorder
nbd_co_client_start() to ensure that all initialization occurs
before we ever try talking to a client in nbd_negotiate(), so
that the teardown sequence on negotiation failure doesn't fault
while dereferencing a half-initialized object.
While debugging this, I also noticed that nbd_update_server_watch()
called by nbd_client_closed() was still adding a channel to accept
the next client, even when the state was no longer RUNNING. That
is fixed by making nbd_can_accept() pay attention to the current
state.
Fixes: https://bugzilla.redhat.com/show_bug.cgi?id=1451614
Signed-off-by: Eric Blake <eblake@redhat.com>
Message-Id: <20170527030421.28366-1-eblake@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
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There a lot of calls of these functions, which already have errp, which
they are filling themselves. On the other hand, nbd_wr_syncv has errp
parameter too, so it would be great to connect them.
Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
Message-Id: <20170516094533.6160-5-vsementsov@virtuozzo.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
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functions read_sync, drop_sync, write_sync, and also
nbd_negotiate_write, nbd_negotiate_read, nbd_negotiate_drop_sync
returns number of processed bytes. But what this number can be,
except requested number of bytes?
Actually, underlying nbd_wr_syncv function returns a value >= 0 and
!= requested_bytes only on eof on read operation. So, firstly, it is
impossible on write (let's add an assert) and on read it actually
means, that communication is broken (except nbd_receive_reply, see
below).
Most of callers operate like this:
if (func(..., size) != size) {
/* error path */
}
, i.e.:
1. They are not interested in partial success
2. Extra duplications in code (especially bad are duplications of
magic numbers)
3. User doesn't see actual error message, as return code is lost.
(this patch doesn't fix this point, but it makes fixing easier)
Several callers handles ret >= 0 and != requested-size separately, by
just returning EINVAL in this case. This patch makes read_sync and
friends return EINVAL in this case, so final behavior is the same.
And only one caller - nbd_receive_reply() does something not so
obvious. It returns EINVAL for ret > 0 and != requested-size, like
previous group, but for ret == 0 it returns 0. The only caller of
nbd_receive_reply() - nbd_read_reply_entry() handles ret == 0 in the
same way as ret < 0, so for now it doesn't matter. However, in
following commits error path handling will be improved and we'll need
to distinguish success from fail in this case too. So, this patch adds
separate helper for this case - read_sync_eof.
Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
Message-Id: <20170516094533.6160-3-vsementsov@virtuozzo.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
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