The patch titled
Subject: ipc/util.c: further ipc_idr_alloc() cleanups
has been added to the -mm tree. Its filename is
ipc-utilc-further-ipc_idr_alloc-cleanups.patch
This patch should soon appear at
http://ozlabs.org/~akpm/mmots/broken-out/ipc-utilc-further-ipc_idr_alloc-cleanups.patch
and later at
http://ozlabs.org/~akpm/mmotm/broken-out/ipc-utilc-further-ipc_idr_alloc-cleanups.patch
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------------------------------------------------------
From: Manfred Spraul <manfred@xxxxxxxxxxxxxxxx>
Subject: ipc/util.c: further ipc_idr_alloc() cleanups
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 anyway: on error, just return, do not set new->id. And
improve the documentation.
Link: http://lkml.kernel.org/r/20180709151019.1336-13-manfred@xxxxxxxxxxxxxxxx
Signed-off-by: Manfred Spraul <manfred@xxxxxxxxxxxxxxxx>
Cc: Dmitry Vyukov <dvyukov@xxxxxxxxxx>
Cc: Davidlohr Bueso <dave@xxxxxxxxxxxx>
Cc: Herbert Xu <herbert@xxxxxxxxxxxxxxxxxxx>
Cc: Kees Cook <keescook@xxxxxxxxxxxx>
Cc: Michael Kerrisk <mtk.manpages@xxxxxxxxx>
Cc: Michal Hocko <mhocko@xxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
ipc/util.c | 22 ++++++++++++++++------
1 file changed, 16 insertions(+), 6 deletions(-)
diff -puN ipc/util.c~ipc-utilc-further-ipc_idr_alloc-cleanups ipc/util.c
--- a/ipc/util.c~ipc-utilc-further-ipc_idr_alloc-cleanups
+++ a/ipc/util.c
@@ -182,11 +182,20 @@ static struct kern_ipc_perm *ipc_findkey
}
/*
- * 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 i
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;
}
/**
_
Patches currently in -mm which might be from manfred@xxxxxxxxxxxxxxxx are
ipc-reorganize-initialization-of-kern_ipc_permid.patch
ipc-reorganize-initialization-of-kern_ipc_permseq.patch
ipc-utilc-use-ipc_rcu_putref-for-failues-in-ipc_addid.patch
ipc-rename-ipcctl_pre_down_nolock.patch
ipc-utilc-correct-comment-in-ipc_obtain_object_check.patch
ipc-rename-ipc_lock-to-ipc_lock_idr.patch
ipc-utilc-further-ipc_idr_alloc-cleanups.patch
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