Messages in this thread | | | Date | Fri, 18 Apr 2014 11:26:02 +0200 | From | Manfred Spraul <> | Subject | Re: [PATCH v3] ipc,shm: disable shmmax and shmall by default |
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Hi Davidlohr,
On 04/18/2014 03:25 AM, Davidlohr Bueso wrote: > So a value of 0 bytes or pages, for shmmax and shmall, respectively, > implies unlimited memory, as opposed to disabling sysv shared memory. That might be a second risk: Right now, a sysadmin can prevent sysv memory allocations with
# sysctl kernel.shmall=0
After your patch is applied, this line allows unlimited allocations.
Obviously my patch has the opposite problem: 64-bit wrap-arounds.
> --- a/include/uapi/linux/shm.h > +++ b/include/uapi/linux/shm.h > @@ -9,14 +9,14 @@ > > /* > * SHMMAX, SHMMNI and SHMALL are upper limits are defaults which can > - * be increased by sysctl > + * be modified by sysctl. By default, disable SHMMAX and SHMALL with > + * 0 bytes, thus allowing processes to have unlimited shared memory. > */ > - > -#define SHMMAX 0x2000000 /* max shared seg size (bytes) */ > +#define SHMMAX 0 /* max shared seg size (bytes) */ > #define SHMMIN 1 /* min shared seg size (bytes) */ > #define SHMMNI 4096 /* max num of segs system wide */ > #ifndef __KERNEL__ > -#define SHMALL (SHMMAX/getpagesize()*(SHMMNI/16)) > +#define SHMALL 0 > #endif > #define SHMSEG SHMMNI /* max shared segs per process */ > The "#ifndef __KERNEL__" is not required: As there is no reference to PAGE_SIZE anymore, one definition for SHMALL is sufficient.
-- Manfred
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