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b=Lz0OiT9qaG0boSebBAdR4hQa2tW/fvX8ob8SWG64CXwPm8OfWGeytVYz6jsHwyBVj EvYhcIg5bqu8eRH+g6dcP+SD7osy4Bm9LGDQ6dHVorUS5sDSoWfC1oAd6NhaZi4Ekb qfPpkLEKWXOP42y5LOdVafC4R1R1lgUQxepI9OLIN9qAK/T7c3UxHdZEvcN+jsN2q2 S4gN8caEzSNVj5cAXlYzLaDm88idbZ4MwflXMyO9keDs34DEqJCVlQSrjZuh7vCFIy 2qXiv1LfO3SzrkoIUzly0jvJRFvqBR2p8vgAdWxdj9ap0mvmeiujtp2YqfwnAzaBf5 dLsQLc0wOnRZQ== Date: Sun, 10 Apr 2022 23:14:49 -0700 From: Eric Biggers To: Dongliang Mu Message-ID: References: <20220408052207.209856-1-dzm91@hust.edu.cn> <7e896205-027d-32e2-32b5-8951231132ac@kernel.org> <2f5b7291-da06-0895-8e75-c7a37251b47e@kernel.org> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: X-Headers-End: 1ndnKG-00CRNp-88 Subject: Re: [f2fs-dev] [PATCH] fs: f2fs: remove WARN_ON in f2fs_is_valid_blkaddr X-BeenThere: linux-f2fs-devel@lists.sourceforge.net X-Mailman-Version: 2.1.21 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: syzbot+763ae12a2ede1d99d4dc@syzkaller.appspotmail.com, linux-kernel , linux-f2fs-devel@lists.sourceforge.net, Dongliang Mu , Jaegeuk Kim , Dmitry Vyukov Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Errors-To: linux-f2fs-devel-bounces@lists.sourceforge.net On Mon, Apr 11, 2022 at 01:06:09PM +0800, Dongliang Mu wrote: > On Mon, Apr 11, 2022 at 11:10 AM Chao Yu wrote: > > > > On 2022/4/9 14:42, Dongliang Mu wrote: > > > On Sat, Apr 9, 2022 at 11:46 AM Chao Yu wrote: > > >> > > >> On 2022/4/9 9:34, Dongliang Mu wrote: > > >>> On Sat, Apr 9, 2022 at 8:27 AM Chao Yu wrote: > > >>>> > > >>>> On 2022/4/8 13:22, Dongliang Mu wrote: > > >>>>> From: Dongliang Mu > > >>>>> > > >>>>> In f2fs_is_valid_blkaddr, if type is DATA_GENERIC_ENHANCE or > > >>>>> DATA_GENERIC_ENHANCE_READ, it invokes WARN_ON(1) not matter > > >>>>> blkaddr is in the range or not. > > >>>> > > >>>> If we run into the path where we invoke WARN_ON(1) in f2fs_is_valid_blkaddr(), > > >>>> It means f2fs image may be broken, or there is a bug in f2fs. > > >>>> > > >>>> So, do you suffer any related issue in your environment? > > >>> > > >>> related issue? Can you explain a little? > > >>> > > >>> If you mean if this warning occurs, any other issues or crash > > >> > > >> I mean have you seen any warning info printed in the path of > > >> f2fs_is_valid_blkaddr() before applying this patch, and if so, w/ what > > >> reproducer? or you just figure out this patch from perspective of code > > >> review? > > > > > > Yes, I have seen both warning information from Syzbot [1] and my local > > > syzkaller instance. > > > > > > In f2fs_is_valid_blkaddr, if the following condition is satisfied, > > > i.e., blkaddr is not in the right range [2], it will directly invoke > > > one WARN_ON. > > > > > > if (unlikely(blkaddr >= MAX_BLKADDR(sbi) || > > > blkaddr < MAIN_BLKADDR(sbi))) { > > > > > > This is the case on Syzbot. > > > > > > Otherwise, it will jump into __is_bitmap_valid. And if the following > > > condition is satisfied [3], it will trigger another WARN_ON. > > > > > > exist = f2fs_test_bit(offset, se->cur_valid_map); > > > if (!exist && type == DATA_GENERIC_ENHANCE) { > > > > > > This appears in my local syzbot instance, but unfortunately it does > > > not get any reproducer. > > > > Oh, it occurs in syzbot test, I guess it is possible that f2fs prints such > > warning info after blkaddr of node/data block was fuzzed to invalid one. > > > > I prefer to keep WARN_ON() to catch more info of bugs found by non-fuzzed > > type test. > > > > Thoughts? > > I am fine with both options. I can remove the WARN_ON in my local > syzkaller instance and continue fuzzing Linux kernel. > > +Dmitry Vyukov how do you think? If WARN_ON is kept, this crash will > occur on Syzbot from time to time. WARN_ON is for kernel bugs; please refer to the documentation in include/asm-generic/bug.h. If this is a kernel bug, then the kernel bug needs to be fixed. Otherwise, the WARN_ON needs to be removed. - Eric _______________________________________________ Linux-f2fs-devel mailing list Linux-f2fs-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/linux-f2fs-devel