* Dhaval Giani <[email protected]> [2009-06-19 00:09:42]:
> On Thu, Jun 18, 2009 at 10:52:17PM +0530, Balbir Singh wrote:
> > * Ivana Varekova <[email protected]> [2009-06-18 07:50:30]:
> >
> > > This patche add a test to cgroup_init function, which prevent to add
> > > multiple records for the same controller (this is a problem eg. in
> > > cgroup_get_cgroup function - which looks to mount table and add all
> > > relevant controllers using cgroup_add_controller function and when the
> > > function calls cgroup_add_cgroup function twice on the same controller,
> > > it returns error so the result is cgroup_get_cgroup failed).
> > >
> > > Signed-off-by: Ivana Varekova <[email protected]>
> > > ---
> > >
> > > src/api.c | 18 ++++++++++++++++++
> > > 1 files changed, 18 insertions(+), 0 deletions(-)
> > >
> > > diff --git a/src/api.c b/src/api.c
> > > index 4f88d20..097060c 100644
> > > --- a/src/api.c
> > > +++ b/src/api.c
> > > @@ -570,6 +570,8 @@ int cgroup_init()
> > > char subsys_name[FILENAME_MAX];
> > > int hierarchy, num_cgroups, enabled;
> > > int i=0;
> > > + int j;
> > > + int duplicate = 0;
> > > char *mntopt = NULL;
> > > int err;
> > > char *buf = NULL;
> > > @@ -648,6 +650,22 @@ int cgroup_init()
> > > continue;
> > >
> > > cgroup_dbg("matched %s:%s\n", mntopt, controllers[i]);
> > > +
> > > + /* do not have duplicates in mount table */
> > > + duplicate = 0;
> > > + for (j = 0; j < found_mnt; j++) {
> > > + if (strncmp(mntopt, cg_mount_table[j].name,
> > > FILENAME_MAX)
> >
> > The length to strncmp() should be the shortest length, in our case
> > it should strlen(cg_mount_table[j].name). We can't rely on maximum
> > length or length of input.
> >
>
> Are you sure it should be the shortest length? So what will happen when
> mntopt says cpu and cg_mount_table[j].name says cpuset?
Good point, lets consider
1. mntopt is cpu and cg_mount_table[j].name is cpuset, strlen is 6 so
strncmp will fail as expected
2. mntopt is cpuset and cg_mount_table[j].name is cpu, strlen is 3 and
strcmp will succeed
So the shortest length still holds true, looks like we need to set the
length to strlen(mntopt).
I think the correct answer is to use
strlen(cg_mount_table[j].name) + 1
or to use strcmp() directly, which I don't like very much
>
> Anyway, the size of cg_mount_table[j].name is FILENAME_MAX.
>
--
Balbir
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