On Mon, May 07, 2018 at 07:57:12PM -0400, Waiman Long wrote:
> On 05/07/2018 06:39 PM, Luis R. Rodriguez wrote:
> > On Mon, May 07, 2018 at 04:59:09PM -0400, Waiman Long wrote:
> >> A user can write arbitrary integer values to msgmni and shmmni sysctl
> >> parameters without getting error, but the actual limit is really
> >> IPCMNI (32k). This can mislead users as they think they can get a
> >> value that is not real.
> >>
> >> The right limits are now set for msgmni and shmmni so that the users
> >> will become aware if they set a value outside of the acceptable range.
> >>
> >> Signed-off-by: Waiman Long <longman@xxxxxxxxxx>
> >> ---
> >> ipc/ipc_sysctl.c | 7 +++++--
> >> 1 file changed, 5 insertions(+), 2 deletions(-)
> >>
> >> diff --git a/ipc/ipc_sysctl.c b/ipc/ipc_sysctl.c
> >> index 8ad93c2..f87cb29 100644
> >> --- a/ipc/ipc_sysctl.c
> >> +++ b/ipc/ipc_sysctl.c
> >> @@ -99,6 +99,7 @@ static int proc_ipc_auto_msgmni(struct ctl_table *table, int write,
> >> static int zero;
> >> static int one = 1;
> >> static int int_max = INT_MAX;
> >> +static int ipc_mni = IPCMNI;
> >>
> >> static struct ctl_table ipc_kern_table[] = {
> >> {
> >> @@ -120,7 +121,9 @@ static int proc_ipc_auto_msgmni(struct ctl_table *table, int write,
> >> .data = &init_ipc_ns.shm_ctlmni,
> >> .maxlen = sizeof(init_ipc_ns.shm_ctlmni),
> >> .mode = 0644,
> >> - .proc_handler = proc_ipc_dointvec,
> >> + .proc_handler = proc_ipc_dointvec_minmax,
> >> + .extra1 = &zero,
> >> + .extra2 = &ipc_mni,
> >> },
> >> {
> >> .procname = "shm_rmid_forced",
> >> @@ -147,7 +150,7 @@ static int proc_ipc_auto_msgmni(struct ctl_table *table, int write,
> >> .mode = 0644,
> >> .proc_handler = proc_ipc_dointvec_minmax,
> >> .extra1 = &zero,
> >> - .extra2 = &int_max,
> >> + .extra2 = &ipc_mni,
> >> },
> >> {
> >> .procname = "auto_msgmni",
> >> --
> >> 1.8.3.1
> > It seems negative values are not allowed, if true then having
> > a caller to use proc_douintvec_minmax() would help with ensuring
> > no invalid negative input values are used as well.
> >
> > Luis
>
> Negative value doesn't mean sense here. So it is true that we can use
> proc_douintvec_minmax() instead. However, the data types themselves are
> defined as "int". So I think it is better to keep using
> proc_dointvec_minmax() to be consistent with the data type.
Huh, no... If you *know* the valid values *are* only positive, the right
thing to do is to then *change* the data type. Tons of odd bugs can creep
up because of these stupid things.
Luis
