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bh=nPISskw1u7gTezcBFKGB27siJLM6bf4b0Rkml2yUaYI=; b=IhwZjWdRb1lf27UFJxA1Jl8DG1T5I6yQqHz508EoPDBn7Bu8W6DPGIK5A+VtrXVxE/6KGI Itw2sZ9HBTvPb1L9jvRKuB5soKRnlmG9LzMEkrPRZxqE/S1yeEQK/vnZX2mR87eC4sp3Yh SsoflcA3SHxAvqv0KLe3NruHE8fKDbA= X-MC-Unique: rAksF0RFMuKCnCVz5eaPRA-1 From: Eric Blake To: qemu-devel@nongnu.org Subject: [PATCH v2 2/2] block: Call attention to truncation of long NBD exports Date: Wed, 10 Jun 2020 11:37:41 -0500 Message-Id: <20200610163741.3745251-3-eblake@redhat.com> In-Reply-To: <20200610163741.3745251-1-eblake@redhat.com> References: <20200610163741.3745251-1-eblake@redhat.com> MIME-Version: 1.0 X-Scanned-By: MIMEDefang 2.84 on 10.5.11.22 X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Transfer-Encoding: quoted-printable Received-SPF: pass (zohomail.com: domain of gnu.org designates 209.51.188.17 as permitted sender) client-ip=209.51.188.17; envelope-from=qemu-devel-bounces+importer=patchew.org@nongnu.org; helo=lists.gnu.org; Received-SPF: pass client-ip=205.139.110.61; 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charset="utf-8" Commit 93676c88 relaxed our NBD client code to request export names up to the NBD protocol maximum of 4096 bytes without NUL terminator, even though the block layer can't store anything longer than 4096 bytes including NUL terminator for display to the user. Since this means there are some export names where we have to truncate things, we can at least try to make the truncation a bit more obvious for the user. Note that in spite of the truncated display name, we can still communicate with an NBD server using such a long export name; this was deemed nicer than refusing to even connect to such a server (since the server may not be under our control, and since determining our actual length limits gets tricky when nbd://host:port/export and nbd+unix:///export?socket=3D/path are themselves variable-length expansions beyond the export name but count towards the block layer name length). Reported-by: Xueqiang Wei Fixes: https://bugzilla.redhat.com/1843684 Signed-off-by: Eric Blake Reviewed-by: Vladimir Sementsov-Ogievskiy --- block.c | 7 +++++-- block/nbd.c | 21 +++++++++++++-------- 2 files changed, 18 insertions(+), 10 deletions(-) diff --git a/block.c b/block.c index 8416376c9b71..6dbcb7e083ea 100644 --- a/block.c +++ b/block.c @@ -6809,8 +6809,11 @@ void bdrv_refresh_filename(BlockDriverState *bs) pstrcpy(bs->filename, sizeof(bs->filename), bs->exact_filename); } else { QString *json =3D qobject_to_json(QOBJECT(bs->full_open_options)); - snprintf(bs->filename, sizeof(bs->filename), "json:%s", - qstring_get_str(json)); + if (snprintf(bs->filename, sizeof(bs->filename), "json:%s", + qstring_get_str(json)) >=3D sizeof(bs->filename)) { + /* Give user a hint if we truncated things. */ + strcpy(bs->filename + sizeof(bs->filename) - 4, "..."); + } qobject_unref(json); } } diff --git a/block/nbd.c b/block/nbd.c index 4ac23c8f6299..eed160c5cda1 100644 --- a/block/nbd.c +++ b/block/nbd.c @@ -1984,6 +1984,7 @@ static void nbd_refresh_filename(BlockDriverState *bs) { BDRVNBDState *s =3D bs->opaque; const char *host =3D NULL, *port =3D NULL, *path =3D NULL; + size_t len =3D 0; if (s->saddr->type =3D=3D SOCKET_ADDRESS_TYPE_INET) { const InetSocketAddress *inet =3D &s->saddr->u.inet; @@ -1996,17 +1997,21 @@ static void nbd_refresh_filename(BlockDriverState *= bs) } /* else can't represent as pseudo-filename */ if (path && s->export) { - snprintf(bs->exact_filename, sizeof(bs->exact_filename), - "nbd+unix:///%s?socket=3D%s", s->export, path); + len =3D snprintf(bs->exact_filename, sizeof(bs->exact_filename), + "nbd+unix:///%s?socket=3D%s", s->export, path); } else if (path && !s->export) { - snprintf(bs->exact_filename, sizeof(bs->exact_filename), - "nbd+unix://?socket=3D%s", path); + len =3D snprintf(bs->exact_filename, sizeof(bs->exact_filename), + "nbd+unix://?socket=3D%s", path); } else if (host && s->export) { - snprintf(bs->exact_filename, sizeof(bs->exact_filename), - "nbd://%s:%s/%s", host, port, s->export); + len =3D snprintf(bs->exact_filename, sizeof(bs->exact_filename), + "nbd://%s:%s/%s", host, port, s->export); } else if (host && !s->export) { - snprintf(bs->exact_filename, sizeof(bs->exact_filename), - "nbd://%s:%s", host, port); + len =3D snprintf(bs->exact_filename, sizeof(bs->exact_filename), + "nbd://%s:%s", host, port); + } + if (len > sizeof(bs->exact_filename)) { + /* Name is too long to represent exactly, so leave it empty. */ + bs->exact_filename[0] =3D '\0'; } } --=20 2.27.0