Messages in this thread | | | Date | Tue, 27 Jan 2009 15:00:21 -0800 | From | Andrew Morton <> | Subject | Re: [PATCH 2/2] make shm_get_stat() more robust |
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On Tue, 27 Jan 2009 17:48:13 -0500 Tony Battersby <tonyb@cybernetics.com> wrote:
> shm_get_stat() assumes idr_find(&shm_ids(ns).ipcs_idr) returns > "struct shmid_kernel *"; all other callers assume that it returns > "struct kern_ipc_perm *". This works because "struct kern_ipc_perm" > is currently the first member of "struct shmid_kernel", but it would > be better to use container_of() to prevent future breakage. > > Signed-off-by: Tony Battersby <tonyb@cybernetics.com> > --- > --- linux-2.6.29-rc2-git3/ipc/shm.c.orig 2009-01-27 16:23:10.000000000 -0500 > +++ linux-2.6.29-rc2-git3/ipc/shm.c 2009-01-27 16:24:19.000000000 -0500 > @@ -551,12 +551,14 @@ static void shm_get_stat(struct ipc_name > in_use = shm_ids(ns).in_use; > > for (total = 0, next_id = 0; total < in_use; next_id++) { > + struct kern_ipc_perm *ipc; > struct shmid_kernel *shp; > struct inode *inode; > > - shp = idr_find(&shm_ids(ns).ipcs_idr, next_id); > - if (shp == NULL) > + ipc = idr_find(&shm_ids(ns).ipcs_idr, next_id); > + if (ipc == NULL) > continue; > + shp = container_of(ipc, struct shmid_kernel, shm_perm); > > inode = shp->shm_file->f_path.dentry->d_inode; >
yup, well spotted.
It would be good to add a little typesafe wrapper:
static inline struct kern_ipc_perm *shm_idr_find(struct ipc_ids *ipc_ids) { return idr_find(&ipc_ids->ipcs_idr); }
(or similar)
so that this sort of mistake cannot happen again.
As you've found, open-coded use of a bare void*-returning function is a bit dangerous.
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