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Date: Wed, 15 Mar 2023 18:32:17 +0100 From: Jan Kara <jack@...e.cz> To: Ivan Zahariev <famzah@...soft.com> Cc: Jan Kara <jack@...e.cz>, Theodore Ts'o <tytso@....edu>, linux-ext4@...r.kernel.org, Greg Kroah-Hartman <gregkh@...uxfoundation.org> Subject: Re: kernel BUG at fs/ext4/inode.c:1914 - page_buffers() On Wed 15-03-23 13:27:11, Ivan Zahariev wrote: > On 12.1.2023 г. 17:07, Jan Kara wrote: > > So after a bit of thought I agree that the commit 5c48a7df91499 ("ext4: fix > > an use-after-free issue about data=journal writeback mode") is broken. The > > problem is when we unlock the page in __ext4_journalled_writepage() anybody > > else can come, writeout the page, and reclaim page buffers (due to memory > > pressure). Previously, bh references were preventing the buffer reclaim to > > happen but now there's nothing to prevent it. > > > > My rewrite of data=journal writeback path fixes this problem as a > > side-effect but perhaps we need a quickfix for stable kernels? Something > > like attached patch? > > > > Honza > > Do you consider this patch production ready? Ah, the patch has likely fallen through the cracks because I waited for some reply and then forgot about it and Ted likely missed it inside the thread. But yes I consider the patch safe to test on production machines - at least it has passed testing with fstests on my test VM without any visible issues. Honza -- Jan Kara <jack@...e.com> SUSE Labs, CR
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