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Date: Wed, 30 Mar 2022 08:51:21 +0900 From: Dominique Martinet <asmadeus@...ewreck.org> To: Tetsuo Handa <penguin-kernel@...ove.SAKURA.ne.jp> Cc: Andrew Perepechko <andrew.perepechko@....com>, Andreas Dilger <adilger@...ger.ca>, Theodore Ts'o <tytso@....edu>, syzbot <syzbot+bde0f89deacca7c765b8@...kaller.appspotmail.com>, linux-kernel@...r.kernel.org, syzkaller-bugs@...glegroups.com, v9fs-developer@...ts.sourceforge.net, "open list:EXT4 FILE SYSTEM" <linux-ext4@...r.kernel.org> Subject: Re: [syzbot] possible deadlock in p9_write_work Tetsuo Handa wrote on Wed, Mar 30, 2022 at 07:35:47AM +0900: > This seems to be an example of > https://lkml.kernel.org/r/49925af7-78a8-a3dd-bce6-cfc02e1a9236@I-love.SAKURA.ne.jp > introduced by "ext4: truncate during setxattr leads to kernel panic". Thanks for the pointer > Please don't use schedule_work() if you need to use flush_scheduled_work(). In this case we don't call flush_scheduled_work -- ext4 does. The problem is mixing in the two subsystems when someone (e.g. syzbot) opens an ext4 file and passes that fd to 9p when mounting with e.g. mount -t 9p -o rfdno=<no>,wfdno=<no> Frankly that's just not something I consider useful, interacting through 9p to a local file doesn't make sense except for testing. If that is a real problem, the simplest way out would be to just forbid non-socket FDs if it's something we can check. -- Dominique
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