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Date: Fri, 30 Oct 2020 09:23:38 +0800 From: yangerkun <yangerkun@...wei.com> To: Ritesh Harjani <riteshh@...ux.ibm.com>, <adilger@...ger.ca> CC: <tytso@....edu>, <jack@...e.com>, <linux-ext4@...r.kernel.org> Subject: Re: [PATCH] ext4: do not use extent after put_bh 在 2020/10/30 0:08, Ritesh Harjani 写道: > > > On 10/28/20 11:26 AM, yangerkun wrote: >> ext4_ext_search_right will read more extent block and call put_bh after >> we get the information we need. However ret_ex will break this and may >> cause use-after-free once pagecache has been freed. Fix it by dup the >> extent we need. > > > It would be good if we have a test case to reproduce it. Do you? > Ideally it should go in fstests, if you have some way to forcefully > reproduce it/simulate it. Let me know, if needed, I can as well help to > get those into fstests. Sorry for that. I found this bug while reading source code. Not with a testcase. And time leave for drop pagecache is so small(time between get_implied_cluster_alloc and ext4_ext_search_right in ext4_ext_map_blocks, other caller for ext4_ext_search_right won't use @ret_ex). It may difficult to reproduce it expect a delay injection. Thanks, Kun. > > -ritesh > .
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