Messages in this thread | | | Date | Tue, 15 Mar 2011 09:51:37 -0400 | From | Christoph Hellwig <> | Subject | Re: [PATCH 0/2] suck some poison out of cgroups' linked lists |
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On Tue, Mar 15, 2011 at 03:08:41PM +0200, Phil Carmody wrote: > Apparently, whether nodes are on a list is being checked with list_empty(), > and if they're on a list, they're list_del()ed. According to a subsequent > list_empty() check, they're still on a list, as list_del() doesn't turn > the nodes into singleton lists, it simply poisons both its pointers, and > merry poison dereferencing may ensue. Oops. > > There are at least 2 to address this matter, I've gone for the latter: > > 1) Do not use list_empty() to check if a node is on a list or not. Have > an additional new function that checks to see whether the node is either > a singleton or is poisoned. Something like list_node_{on,off}_list()? > > 2) Ensure that you never leave poison anywhere where you might want > to use list_empty().
The correct way is to use list_del_init() if you want to do list_empty checks later on.
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