If idr_alloc within ipc_idr_alloc fails, then the return value (-ENOSPC)
is used to calculate new->id.
Technically, this is not a bug, because new->id is never accessed.
But: Clean it up anyways: On error, just return, do not set new->id.
And improve the documentation.
Signed-off-by: Manfred Spraul <manf...@colorfullife.com>
Cc: Dmitry Vyukov <dvyu...@google.com>
---
ipc/util.c | 22 ++++++++++++++++------
1 file changed, 16 insertions(+), 6 deletions(-)
diff --git a/ipc/util.c b/ipc/util.c
index d474f2b3b299..302c18fc846b 100644
--- a/ipc/util.c
+++ b/ipc/util.c
@@ -182,11 +182,20 @@ static struct kern_ipc_perm *ipc_findkey(struct ipc_ids
*ids, key_t key)
}
/*
- * Specify desired id for next allocated IPC object.
+ * Insert new IPC object into idr tree, and set sequence number and id
+ * in the correct order.
+ * Especially:
+ * - the sequence number must be set before inserting the object into the idr,
+ * because the sequence number is accessed without a lock.
+ * - the id can/must be set after inserting the object into the idr.
+ * All accesses must be done after getting kern_ipc_perm.lock.
+ *
+ * The caller must own kern_ipc_perm.lock.of the new object.
+ * On error, the function returns a (negative) error code.
*/
static inline int ipc_idr_alloc(struct ipc_ids *ids, struct kern_ipc_perm *new)
{
- int key, next_id = -1;
+ int id, next_id = -1;
#ifdef CONFIG_CHECKPOINT_RESTORE
next_id = ids->next_id;
@@ -197,14 +206,15 @@ static inline int ipc_idr_alloc(struct ipc_ids *ids,
struct kern_ipc_perm *new)
new->seq = ids->seq++;
if (ids->seq > IPCID_SEQ_MAX)
ids->seq = 0;
- key = idr_alloc(&ids->ipcs_idr, new, 0, 0, GFP_NOWAIT);
+ id = idr_alloc(&ids->ipcs_idr, new, 0, 0, GFP_NOWAIT);
} else {
new->seq = ipcid_to_seqx(next_id);
- key = idr_alloc(&ids->ipcs_idr, new, ipcid_to_idx(next_id),
+ id = idr_alloc(&ids->ipcs_idr, new, ipcid_to_idx(next_id),
0, GFP_NOWAIT);
}
- new->id = SEQ_MULTIPLIER * new->seq + key;
- return key;
+ if (id >= 0)
+ new->id = SEQ_MULTIPLIER * new->seq + id;
+ return id;
}
/**
--
2.17.1
