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Fri, 25 Oct 2024 23:04:04 +0200 Message-ID: Date: Sat, 26 Oct 2024 07:33:59 +1030 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH] btrfs: add a sanity check for btrfs root To: dsterba@suse.cz Cc: Lizhi Xu , syzbot+3030e17bd57a73d39bd7@syzkaller.appspotmail.com, clm@fb.com, dsterba@suse.com, josef@toxicpanda.com, linux-btrfs@vger.kernel.org, linux-kernel@vger.kernel.org, syzkaller-bugs@googlegroups.com References: <6719c407.050a0220.10f4f4.01dc.GAE@google.com> <20241025045553.2012160-1-lizhi.xu@windriver.com> <03bcaafe-4a15-487a-af2b-b23970162bbb@gmx.com> <20241025180315.GI31418@twin.jikos.cz> Content-Language: en-US From: Qu Wenruo Autocrypt: addr=quwenruo.btrfs@gmx.com; keydata= xsBNBFnVga8BCACyhFP3ExcTIuB73jDIBA/vSoYcTyysFQzPvez64TUSCv1SgXEByR7fju3o 8RfaWuHCnkkea5luuTZMqfgTXrun2dqNVYDNOV6RIVrc4YuG20yhC1epnV55fJCThqij0MRL 1NxPKXIlEdHvN0Kov3CtWA+R1iNN0RCeVun7rmOrrjBK573aWC5sgP7YsBOLK79H3tmUtz6b 9Imuj0ZyEsa76Xg9PX9Hn2myKj1hfWGS+5og9Va4hrwQC8ipjXik6NKR5GDV+hOZkktU81G5 gkQtGB9jOAYRs86QG/b7PtIlbd3+pppT0gaS+wvwMs8cuNG+Pu6KO1oC4jgdseFLu7NpABEB AAHNIlF1IFdlbnJ1byA8cXV3ZW5ydW8uYnRyZnNAZ214LmNvbT7CwJQEEwEIAD4CGwMFCwkI BwIGFQgJCgsCBBYCAwECHgECF4AWIQQt33LlpaVbqJ2qQuHCPZHzoSX+qAUCZxF1YAUJEP5a sQAKCRDCPZHzoSX+qF+mB/9gXu9C3BV0omDZBDWevJHxpWpOwQ8DxZEbk9b9LcrQlWdhFhyn xi+l5lRziV9ZGyYXp7N35a9t7GQJndMCFUWYoEa+1NCuxDs6bslfrCaGEGG/+wd6oIPb85xo naxnQ+SQtYLUFbU77WkUPaaIU8hH2BAfn9ZSDX9lIxheQE8ZYGGmo4wYpnN7/hSXALD7+oun tZljjGNT1o+/B8WVZtw/YZuCuHgZeaFdhcV2jsz7+iGb+LsqzHuznrXqbyUQgQT9kn8ZYFNW 7tf+LNxXuwedzRag4fxtR+5GVvJ41Oh/eygp8VqiMAtnFYaSlb9sjia1Mh+m+OBFeuXjgGlG VvQFzsBNBFnVga8BCACqU+th4Esy/c8BnvliFAjAfpzhI1wH76FD1MJPmAhA3DnX5JDORcga CbPEwhLj1xlwTgpeT+QfDmGJ5B5BlrrQFZVE1fChEjiJvyiSAO4yQPkrPVYTI7Xj34FnscPj /IrRUUka68MlHxPtFnAHr25VIuOS41lmYKYNwPNLRz9Ik6DmeTG3WJO2BQRNvXA0pXrJH1fN GSsRb+pKEKHKtL1803x71zQxCwLh+zLP1iXHVM5j8gX9zqupigQR/Cel2XPS44zWcDW8r7B0 q1eW4Jrv0x19p4P923voqn+joIAostyNTUjCeSrUdKth9jcdlam9X2DziA/DHDFfS5eq4fEv ABEBAAHCwHwEGAEIACYCGwwWIQQt33LlpaVbqJ2qQuHCPZHzoSX+qAUCZxF1gQUJEP5a0gAK CRDCPZHzoSX+qHGpB/kB8A7M7KGL5qzat+jBRoLwB0Y3Zax0QWuANVdZM3eJDlKJKJ4HKzjo B2Pcn4JXL2apSan2uJftaMbNQbwotvabLXkE7cPpnppnBq7iovmBw++/d8zQjLQLWInQ5kNq Vmi36kmq8o5c0f97QVjMryHlmSlEZ2Wwc1kURAe4lsRG2dNeAd4CAqmTw0cMIrR6R/Dpt3ma +8oGXJOmwWuDFKNV4G2XLKcghqrtcRf2zAGNogg3KulCykHHripG3kPKsb7fYVcSQtlt5R6v HZStaZBzw4PcDiaAF3pPDBd+0fIKS6BlpeNRSFG94RYrt84Qw77JWDOAZsyNfEIEE0J6LSR/ In-Reply-To: <20241025180315.GI31418@twin.jikos.cz> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: quoted-printable X-Provags-ID: V03:K1:5SKQGQGus0ODslVp11cF3lEdunMDzTif1PxUptWtrc1tvm3hqDz YunZj0Iscr/3v7q/f367yf4CbWxVmvlHQ+mcH4Ib/VbCj/mpgXuQ90xbzn/VMP2BB9Dv4tz zasDCSPVfaWkqqNrP9Tc0/+gc2yWwvIOQdktx9/N7Ei4aXd+JUG2BzVKCi/xuQH8ZMIQDgT 2nWUwm+vEf1ILjUvM/NUQ== X-Spam-Flag: NO UI-OutboundReport: notjunk:1;M01:P0:ygiZmHliaN8=;7I6evqp2kZUcKH7fpTFs3EmwWOh uB08Fz7/PEJtK3QvQcOjQpKziNAdBdFjk3DBLbApxkS4pkValT4NnPfEVv0Cdli//LUfXiibM oHs0DwcjMiMigIWj682hqkDVMc/DhwQpsna/CXFLgqpQLx3kv8VCC4QMv09NionofJ3x+bGWU ZmxqPs4AepjuPmlEDb8GHSvvMmtyrZcWPrUCLc8GogQTLiemJhdiQHsDn2W52I6IRcITeZzhk mJIRZUERfJ9WnZzFq+Wt9A/jredC/VotGxw6oUS80pujiosBAT3v7l/oTpIJDegRTUC/Mj5vE 5/uyZMUaQq2f8QoH82ot04WILqyeZJ3cTd0TJp2Dfj+p/uYx6ljyV6K9VZK/6k3nHDK5sIUON 4SWu8tWAoQhpVu9aiqu4f+bJy+Lys0/4WE7FbP929enRtElVmiwYJlo2sxhxnTbTErCnfjund /2p2blGO7Csf4fyiPYIgv1TRGnDg4QuQ6xOmjkVDLeapdDBBK3NPlhCpYcBmwYek1upWC0eXO T+wQAfIUGJFMnjmFkN5w6OEXG+WNA8Tos6/pcscdaaAatq6aAUbk8zKdz5VevGKD7ue+tNMKB nj/vw7mDh7u8vLqTOHyUGU9wsGbJUIvvT0aP7dmpiKjLCJE78Bx2uDb5P1vPSJjFXKlpTEBOO 7EvdJRDMyWletuIo6AfDJ1EsMwzoIlSiiJREbQSbAvbHbQqIDUsrVdTBLaOA4cgAeRAnnjf1N KQ/l9wcsPRmpznzhBJN0Qtu6ew211kj1tazgjKcnIE6TRv6rCYjAw6TCuRnYqgWGHjn1MS2Ol ThEW+huQt+kXO+SGtCQNSYFEqxX6bluH9E1kPbWHfMNkU= =E5=9C=A8 2024/10/26 04:33, David Sterba =E5=86=99=E9=81=93: > On Fri, Oct 25, 2024 at 08:23:07PM +1030, Qu Wenruo wrote: >> >> >> =E5=9C=A8 2024/10/25 15:25, Lizhi Xu =E5=86=99=E9=81=93: >>> Syzbot report a null-ptr-deref in btrfs_search_slot. >>> It use the input logical can't find the extent root in extent_from_log= ical, >>> and triger the null-ptr-deref in btrfs_search_slot. >>> Add sanity check for btrfs root before using it in btrfs_search_slot. >> >> Although I'd prefer to explain a little more about why the NULL root >> pointer can happen (caused by the rescue=3Dall mount option), which can >> cause NULL root pointer for non-critical tree roots, like >> uuid/csum/extent or even device trees. >> >> You don't need to bother sending an update. >> I can add such info when pushing to the maintainer's tree. >> >>> >>> Reported-by: syzbot+3030e17bd57a73d39bd7@syzkaller.appspotmail.com >>> Closes: https://syzkaller.appspot.com/bug?extid=3D3030e17bd57a73d39bd7 >>> Signed-off-by: Lizhi Xu >> >> Reviewed-by: Qu Wenruo > >>> @@ -2023,6 +2023,10 @@ int btrfs_search_slot(struct btrfs_trans_handle= *trans, struct btrfs_root *root, >>> int min_write_lock_level; >>> int prev_cmp; >>> >>> + if (!root) >>> + return -EINVAL; > > The function returns errors indirectly so it's not clear which could be > ultimately returned. I did a quick search over the calls starting in > btrfs_search_slot() and it seems that EINVAL is not used so we'd know if > it ends up in some error report. The ones I found: EAGAIN, EIO, EUCLEAN, > ENOMEM. > If you want, I can add extra (ratelimited though) error/warning message for such cases. Considering this is only possible for rescue=3Dall cases, extra error messages should be fine. Or do you prefer some more rare return values? Thanks, Qu