IPC: fix error case when idr-cache is empty in ipcget()

With the use of idr to store the ipc, the case where the idr cache is
empty, when idr_get_new is called (this may happen even if we call
idr_pre_get() before), is not well handled: it lets
semget()/shmget()/msgget() return ENOSPC when this cache is empty, what 1.
does not reflect the facts and 2.  does not conform to the man(s).

This patch fixes this by retrying the whole process of allocation in this case.

Signed-off-by: Pierre Peiffer <pierre.peiffer@bull.net>
Cc: Nadia Derbey <Nadia.Derbey@bull.net>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 3 insertions, 2 deletions

diff --git a/ipc/shm.c b/ipc/shm.c
index 05c97c7513c2..3818fae625c5 100644
--- a/ipc/shm.c
+++ b/ipc/shm.c
@@ -433,10 +433,11 @@ static int newseg(struct ipc_namespace *ns, struct ipc_params *params)
         if (IS_ERR(file))
                 goto no_file;
 
-        error = -ENOSPC;
         id = shm_addid(ns, shp);
-        if(id == -1) 
+        if (id < 0) {
+                error = id;
                 goto no_id;
+        }
 
         shp->shm_cprid = task_tgid_vnr(current);
         shp->shm_lprid = 0;