Messages in this thread Patch in this message | | | From | Manfred Spraul <> | Subject | [PATCH] ipc/sem.c: Synchronize the proc interface | Date | Wed, 25 Sep 2013 17:24:49 +0200 |
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The proc interface is not aware of sem_lock(), it calls ipc_lock_object() directly. This means that simple semop() operations can run in parallel with the proc interface. Right now, this is uncritical, because the implementation doesn't do anything that requires a proper synchronization.
But it is dangerous and therefore should be fixed.
Andrew: - Could you include the patch in -mm and push it towards Linus? - The patch depends on ipc-semc-fix-race-in-sem_lock.patch
Signed-off-by: Manfred Spraul <manfred@colorfullife.com> --- ipc/sem.c | 8 ++++++++ 1 file changed, 8 insertions(+)
diff --git a/ipc/sem.c b/ipc/sem.c index 4a92c04..e5d9bb8 100644 --- a/ipc/sem.c +++ b/ipc/sem.c @@ -2095,6 +2095,14 @@ static int sysvipc_sem_proc_show(struct seq_file *s, void *it) struct sem_array *sma = it; time_t sem_otime; + /* + * The proc interface isn't aware of sem_lock(), it calls + * ipc_lock_object() directly (in sysvipc_find_ipc). + * In order to stay compatible with sem_lock(), we must wait until + * all simple semop() calls have left their critical regions. + */ + sem_wait_array(sma); + sem_otime = get_semotime(sma); return seq_printf(s, -- 1.8.3.1
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