From 5c86bdf1208916ece0b87e1151c9b48ee54faa3e Mon Sep 17 00:00:00 2001 From: Eric Blake Date: Mon, 8 Jun 2020 13:26:38 -0500 Subject: [PATCH] block: Call attention to truncation of long NBD exports 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=/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 Message-Id: <20200610163741.3745251-3-eblake@redhat.com> --- block.c | 7 +++++-- block/nbd.c | 21 +++++++++++++-------- 2 files changed, 18 insertions(+), 10 deletions(-) diff --git a/block.c b/block.c index 8416376c9b..6dbcb7e083 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 = 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)) >= 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 4ac23c8f62..eed160c5cd 100644 --- a/block/nbd.c +++ b/block/nbd.c @@ -1984,6 +1984,7 @@ static void nbd_refresh_filename(BlockDriverState *bs) { BDRVNBDState *s = bs->opaque; const char *host = NULL, *port = NULL, *path = NULL; + size_t len = 0; if (s->saddr->type == SOCKET_ADDRESS_TYPE_INET) { const InetSocketAddress *inet = &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=%s", s->export, path); + len = snprintf(bs->exact_filename, sizeof(bs->exact_filename), + "nbd+unix:///%s?socket=%s", s->export, path); } else if (path && !s->export) { - snprintf(bs->exact_filename, sizeof(bs->exact_filename), - "nbd+unix://?socket=%s", path); + len = snprintf(bs->exact_filename, sizeof(bs->exact_filename), + "nbd+unix://?socket=%s", path); } else if (host && s->export) { - snprintf(bs->exact_filename, sizeof(bs->exact_filename), - "nbd://%s:%s/%s", host, port, s->export); + len = 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 = 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] = '\0'; } }