ipc/shm.c: check for overflows of shm_tot

shm_tot counts the total number of pages used by shm segments.

If SHMALL is ULONG_MAX (or nearly ULONG_MAX), then the number can
overflow.  Subsequent calls to shmctl(,SHM_INFO,) would return wrong
values for shm_tot.

The patch adds a detection for overflows.

Signed-off-by: Manfred Spraul <[email protected]>
Acked-by: Davidlohr Bueso <[email protected]>
Acked-by: KOSAKI Motohiro <[email protected]>
Acked-by: Michael Kerrisk <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>

diff --git a/ipc/shm.c b/ipc/shm.c
index dda8f1ff3c352105f1e1549ac6e3971ef0425251..9e51bf24634463d5ec0e493a6888173d57ac7b0a 100644 (file)
--- a/ipc/shm.c
+++ b/ipc/shm.c
@@ -493,7 +493,8 @@ static int newseg(struct ipc_namespace *ns, struct ipc_params *params)
        if (size < SHMMIN || size > ns->shm_ctlmax)
                return -EINVAL;
 
-       if (ns->shm_tot + numpages > ns->shm_ctlall)
+       if (ns->shm_tot + numpages < ns->shm_tot ||
+                       ns->shm_tot + numpages > ns->shm_ctlall)
                return -ENOSPC;
 
        shp = ipc_rcu_alloc(sizeof(*shp));