The Thursday 15 May 2014 à 08:06:14 (-0400), Jeff Cody wrote : > On Thu, May 15, 2014 at 01:58:59PM +0200, Benoît Canet wrote: > > The Wednesday 14 May 2014 à 23:20:15 (-0400), Jeff Cody wrote : > > > Currently, node_name is only filled in when done so explicitly by the > > > user. If no node_name is specified, then the node name field is not > > > populated. > > > > > > If node_names are automatically generated when not specified, that means > > > that all block job operations can be done by reference to the unique > > > node_name field. This eliminates ambiguity in filename pathing > > > (relative filenames, or file descriptors, symlinks, mounts, etc..) that > > > qemu currently needs to deal with. > > > > > > If a node name is specified, then it will not be automatically > > > generated for that BDS entry. > > > > > > If it is automatically generated, it will be prefaced with "__qemu##", > > > followed by 8 characters of a unique number, followed by 8 random > > > ASCII characters in the range of 'A-Z'. Some sample generated node-name > > > strings: > > > __qemu##00000000IAIYNXXR > > > __qemu##00000002METXTRBQ > > > __qemu##00000001FMBORDWG > > > > > > The prefix is to aid in identifying it as a qemu-generated name, the > > > numeric portion is to guarantee uniqueness in a given qemu session, and > > > the random characters are to further avoid any accidental collisions > > > with user-specified node-names. > > > > > > Signed-off-by: Jeff Cody <jc...@redhat.com> > > > --- > > > block.c | 16 +++++++++++++++- > > > 1 file changed, 15 insertions(+), 1 deletion(-) > > > > > > diff --git a/block.c b/block.c > > > index c90c71a..81945d3 100644 > > > --- a/block.c > > > +++ b/block.c > > > @@ -838,12 +838,26 @@ static int bdrv_open_flags(BlockDriverState *bs, > > > int flags) > > > return open_flags; > > > } > > > > > > +#define GEN_NODE_NAME_PREFIX "__qemu##" > > > +#define GEN_NODE_NAME_MAX_LEN (sizeof(GEN_NODE_NAME_PREFIX) + 8 + 8) > > > static void bdrv_assign_node_name(BlockDriverState *bs, > > > const char *node_name, > > > Error **errp) > > > { > > > + char gen_node_name[GEN_NODE_NAME_MAX_LEN]; > > > > The room for the '\0' string termination seems to be missing: > > > > char gen_node_name[GEN_NODE_NAME_MAX_LEN + 1]; > > > > The array includes room for it, note the use of 'sizeof()': > #define GEN_NODE_NAME_MAX_LEN (sizeof(GEN_NODE_NAME_PREFIX) + 8 + 8) > > sizeof() includes the '\0' in the length, while strlen() does not; > e.g.: > sizeof("four") = 5 > strlen("four") = 4 > > > > + static uint32_t counter; /* simple counter to guarantee uniqueness */ > > > + > > > + /* if node_name is NULL, auto-generate a node name */ > > > if (!node_name) { > > > - return; > > > + int len; > > > + snprintf(gen_node_name, GEN_NODE_NAME_MAX_LEN, > > > + "%s%08x", GEN_NODE_NAME_PREFIX, counter++); > > > + len = strlen(gen_node_name); > > > + while (len < GEN_NODE_NAME_MAX_LEN - 1) { > > > + gen_node_name[len++] = g_random_int_range('A', 'Z'); > > > + } > > > > Is this code generating only 7 random chars instead of 8 ? > > > > It generates 8 random characters (the sample node-name strings in the > commit message were pulled straight from the QMP command > 'query-named-block-nodes') > > > > + gen_node_name[GEN_NODE_NAME_MAX_LEN - 1] = '\0'; > > > > Could be: > > gen_node_name[GEN_NODE_NAME_MAX_LEN] = '\0'; > > if the array is properly declared. > > > > That would go over the array bounds by 1.
Yes I missed the use of sizeof(). I am happy to have learnt that. Sorry for the noise. > > > > + node_name = gen_node_name; > > > } > > > > > > /* empty string node name is invalid */ > > > -- > > > 1.8.3.1 > > >