diff options
| -rw-r--r-- | include/uapi/linux/shm.h | 15 |
1 files changed, 9 insertions, 6 deletions
diff --git a/include/uapi/linux/shm.h b/include/uapi/linux/shm.h index 74e786de6f4e..1fbf24ea37fd 100644 --- a/include/uapi/linux/shm.h +++ b/include/uapi/linux/shm.h @@ -8,17 +8,20 @@ #endif /* - * SHMMAX, SHMMNI and SHMALL are upper limits are defaults which can - * be modified by sysctl. + * SHMMNI, SHMMAX and SHMALL are default upper limits which can be + * modified by sysctl. The SHMMAX and SHMALL values have been chosen to + * be as large possible without facilitating scenarios where userspace + * causes overflows when adjusting the limits via operations of the form + * "retrieve current limit; add X; update limit". It is therefore not + * advised to make SHMMAX and SHMALL any larger. These limits are + * suitable for both 32 and 64-bit systems. */ - #define SHMMIN 1 /* min shared seg size (bytes) */ #define SHMMNI 4096 /* max num of segs system wide */ -#define SHMMAX (ULONG_MAX - (1L<<24)) /* max shared seg size (bytes) */ -#define SHMALL (ULONG_MAX - (1L<<24)) /* max shm system wide (pages) */ +#define SHMMAX (ULONG_MAX - (1UL << 24)) /* max shared seg size (bytes) */ +#define SHMALL (ULONG_MAX - (1UL << 24)) /* max shm system wide (pages) */ #define SHMSEG SHMMNI /* max shared segs per process */ - /* Obsolete, used only for backwards compatibility and libc5 compiles */ struct shmid_ds { struct ipc_perm shm_perm; /* operation perms */ |