On Mon, Nov 26, 2018 at 10:31:39AM +0100, Carlos Maiolino wrote: > On Sat, Nov 24, 2018 at 05:44:20PM +0800, Pan Bian wrote: > > The function xfs_alloc_get_freelist calls xfs_perag_put to drop the > > reference. In this case, pag may be released. However, > > pag->pagf_btreeblks is read and write after the put operation. This may > > result in a use-after-free bug. This patch moves the put operation late. > > > > The patch looks reasonable, can you detail more how did you find it? Via code > inspection of you hit this user-after-free in some way? I wrote a tool to check such bugs statically. It first scans the source code to extract paired alloc/free functions. Equipped with such functions, it performs an intra-procedural data flow analysis to detect mismatched alloc/free bugs and use-after-free bugs. Best regards, Pan Bian
