Messages in this thread | | | Date | Sun, 13 Apr 2008 01:59:36 -0700 | From | Andrew Morton <> | Subject | Re: [PATCH 1/2] fix sys_unshare()+SEM_UNDO: add support for CLONE_SYSVSEM |
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On Sun, 13 Apr 2008 10:04:17 +0200 Manfred Spraul <manfred@colorfullife.com> wrote:
> sys_unshare(CLONE_NEWIPC) doesn't handle the undo lists properly, this can > cause a kernel memory corruption. CLONE_NEWIPC must detach from the existing > undo lists. > Fix, part 1: add support for sys_unshare(CLONE_SYSVSEM) >
Is this a non-back-compatible change?
> > Signed-off-by: Manfred Spraul <manfred@colorfullife.com> > --- > ipc/sem.c | 1 + > kernel/fork.c | 18 ++++++++++++++---- > 2 files changed, 15 insertions(+), 4 deletions(-) > > diff --git a/ipc/sem.c b/ipc/sem.c > index 0b45a4d..35841bd 100644 > --- a/ipc/sem.c > +++ b/ipc/sem.c > @@ -1298,6 +1298,7 @@ void exit_sem(struct task_struct *tsk) > undo_list = tsk->sysvsem.undo_list; > if (!undo_list) > return; > + tsk->sysvsem.undo_list = NULL; > > if (!atomic_dec_and_test(&undo_list->refcnt)) > return; > diff --git a/kernel/fork.c b/kernel/fork.c > index 9c042f9..7f242b0 100644 > --- a/kernel/fork.c > +++ b/kernel/fork.c > @@ -1675,13 +1675,17 @@ static int unshare_fd(unsigned long unshare_flags, struct files_struct **new_fdp > } > > /* > - * Unsharing of semundo for tasks created with CLONE_SYSVSEM is not > - * supported yet > + * Unsharing of semundo for tasks created with CLONE_SYSVSEM doesn't require > + * any allocations: it means that the task leaves the existing undo lists, > + * just like sys_exit(). The new undo lists are allocated on demand in the > + * ipc syscalls. > + * new_ulistp is set to a non-NULL value, the caller expects that on success. > */ > static int unshare_semundo(unsigned long unshare_flags, struct sem_undo_list **new_ulistp) > { > - if (unshare_flags & CLONE_SYSVSEM) > - return -EINVAL; > + if (unshare_flags & CLONE_SYSVSEM) { > + *new_ulistp = (void*)1; > + }
And can we do anything nicer than this?
> return 0; > } > @@ -1731,6 +1735,12 @@ asmlinkage long sys_unshare(unsigned long unshare_flags) > goto bad_unshare_cleanup_semundo; > > if (new_fs || new_mm || new_fd || new_ulist || new_nsproxy) { > + if (unshare_flags & CLONE_SYSVSEM) { > + /* > + * CLONE_SYSVSEM is equivalent to sys_exit(). > + */ > + exit_sem(current); > + } > > if (new_nsproxy) { > switch_task_namespaces(current, new_nsproxy); > -- > 1.5.4.1
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