Messages in this thread Patch in this message | | | From | Manfred Spraul <> | Date | Sun, 13 Apr 2008 10:04:17 +0200 | Subject | [PATCH 1/2] fix sys_unshare()+SEM_UNDO: add support for CLONE_SYSVSEM |
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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)
I'm not sure who's the right maintainer, Andrew, could you merge it?
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; + } 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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