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authorDavidlohr Bueso <dave@stgolabs.net>2015-06-30 14:58:45 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2015-06-30 19:44:59 -0700
commitf8b5918495be32807c4f878de959540eb63a9b9f (patch)
tree4f451f58daf8c894eaf4f3e9bac6d88b597c3881 /ipc
parent55b7ae50167efc9b1c4f8fb60a99478cd46a82f7 (diff)
downloadleg-kernel-f8b5918495be32807c4f878de959540eb63a9b9f.tar.gz
ipc,sysv: make return -EIDRM when racing with RMID consistent
The ipc_lock helper is used by all forms of sysv ipc to acquire the ipc object's spinlock. Upon error (bogus identifier), we always return -EINVAL, whether the problem be in the idr path or because we raced with a task performing RMID. For the later, however, all ipc related manpages, state the that for: EIDRM <ID> points to a removed identifier. And return: EINVAL Invalid <ID> value, or unaligned, etc. Which (EINVAL) should only return once the ipc resource is deleted. For all types of ipc this is done immediately upon a RMID command. However, shared memory behaves slightly different as it can merely mark a segment for deletion, and delay the actual freeing until there are no more active consumers. Per shmctl(IPC_RMID) manpage: "" Mark the segment to be destroyed. The segment will only actually be destroyed after the last process detaches it (i.e., when the shm_nattch member of the associated structure shmid_ds is zero). "" Unlike ipc_lock, paths that behave "correctly", at least per the manpage, involve controlling the ipc resource via *ctl(), doing the exact same validity check as ipc_lock after right acquiring the spinlock: if (!ipc_valid_object()) { err = -EIDRM; goto out_unlock; } Thus make ipc_lock consistent with the rest of ipc code and return -EIDRM in ipc_lock when !ipc_valid_object(). Signed-off-by: Davidlohr Bueso <dbueso@suse.de> Cc: Manfred Spraul <manfred@colorfullife.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'ipc')
-rw-r--r--ipc/util.c13
1 files changed, 8 insertions, 5 deletions
diff --git a/ipc/util.c b/ipc/util.c
index 3fdfabfdd9c3..b99038699fee 100644
--- a/ipc/util.c
+++ b/ipc/util.c
@@ -583,19 +583,22 @@ struct kern_ipc_perm *ipc_lock(struct ipc_ids *ids, int id)
rcu_read_lock();
out = ipc_obtain_object_idr(ids, id);
if (IS_ERR(out))
- goto err1;
+ goto err;
spin_lock(&out->lock);
- /* ipc_rmid() may have already freed the ID while ipc_lock
- * was spinning: here verify that the structure is still valid
+ /*
+ * ipc_rmid() may have already freed the ID while ipc_lock()
+ * was spinning: here verify that the structure is still valid.
+ * Upon races with RMID, return -EIDRM, thus indicating that
+ * the ID points to a removed identifier.
*/
if (ipc_valid_object(out))
return out;
spin_unlock(&out->lock);
- out = ERR_PTR(-EINVAL);
-err1:
+ out = ERR_PTR(-EIDRM);
+err:
rcu_read_unlock();
return out;
}