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[2403:580d:fda1::299]) by smtp.gmail.com with ESMTPSA id d9443c01a7336-2a2f3d4cb25sm319044435ad.56.2025.12.30.20.55.10 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Tue, 30 Dec 2025 20:55:12 -0800 (PST) Message-ID: <9d21022d-5051-4165-b8fa-f77ec7e820ab@suse.com> Date: Wed, 31 Dec 2025 15:25:08 +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: Soft tag and inline kasan triggering NULL pointer dereference, but not for hard tag and outline mode (was Re: [6.19-rc3] xxhash invalid access during BTRFS mount) From: Qu Wenruo To: Daniel J Blueman Cc: David Sterba , Chris Mason , Linux BTRFS , linux-crypto@vger.kernel.org, Linux Kernel , kasan-dev@googlegroups.com, ryabinin.a.a@gmail.com References: <01d84dae-1354-4cd5-97ce-4b64a396316a@suse.com> <642a3e9a-f3f1-4673-8e06-d997b342e96b@suse.com> <17bf8f85-9a9c-4d7d-add7-cd92313f73f1@suse.com> Content-Language: en-US Autocrypt: addr=wqu@suse.com; keydata= xsBNBFnVga8BCACyhFP3ExcTIuB73jDIBA/vSoYcTyysFQzPvez64TUSCv1SgXEByR7fju3o 8RfaWuHCnkkea5luuTZMqfgTXrun2dqNVYDNOV6RIVrc4YuG20yhC1epnV55fJCThqij0MRL 1NxPKXIlEdHvN0Kov3CtWA+R1iNN0RCeVun7rmOrrjBK573aWC5sgP7YsBOLK79H3tmUtz6b 9Imuj0ZyEsa76Xg9PX9Hn2myKj1hfWGS+5og9Va4hrwQC8ipjXik6NKR5GDV+hOZkktU81G5 gkQtGB9jOAYRs86QG/b7PtIlbd3+pppT0gaS+wvwMs8cuNG+Pu6KO1oC4jgdseFLu7NpABEB AAHNGFF1IFdlbnJ1byA8d3F1QHN1c2UuY29tPsLAlAQTAQgAPgIbAwULCQgHAgYVCAkKCwIE FgIDAQIeAQIXgBYhBC3fcuWlpVuonapC4cI9kfOhJf6oBQJnEXVgBQkQ/lqxAAoJEMI9kfOh Jf6o+jIH/2KhFmyOw4XWAYbnnijuYqb/obGae8HhcJO2KIGcxbsinK+KQFTSZnkFxnbsQ+VY fvtWBHGt8WfHcNmfjdejmy9si2jyy8smQV2jiB60a8iqQXGmsrkuR+AM2V360oEbMF3gVvim 2VSX2IiW9KERuhifjseNV1HLk0SHw5NnXiWh1THTqtvFFY+CwnLN2GqiMaSLF6gATW05/sEd V17MdI1z4+WSk7D57FlLjp50F3ow2WJtXwG8yG8d6S40dytZpH9iFuk12Sbg7lrtQxPPOIEU rpmZLfCNJJoZj603613w/M8EiZw6MohzikTWcFc55RLYJPBWQ+9puZtx1DopW2jOwE0EWdWB rwEIAKpT62HgSzL9zwGe+WIUCMB+nOEjXAfvoUPUwk+YCEDcOdfkkM5FyBoJs8TCEuPXGXBO Cl5P5B8OYYnkHkGWutAVlUTV8KESOIm/KJIA7jJA+Ss9VhMjtePfgWexw+P8itFRSRrrwyUf E+0WcAevblUi45LjWWZgpg3A80tHP0iToOZ5MbdYk7YFBE29cDSleskfV80ZKxFv6koQocq0 vXzTfHvXNDELAuH7Ms/WJcdUzmPyBf3Oq6mKBBH8J6XZc9LjjNZwNbyvsHSrV5bgmu/THX2n g/3be+iqf6OggCiy3I1NSMJ5KtR0q2H2Nx2Vqb1fYPOID8McMV9Ll6rh8S8AEQEAAcLAfAQY AQgAJgIbDBYhBC3fcuWlpVuonapC4cI9kfOhJf6oBQJnEXWBBQkQ/lrSAAoJEMI9kfOhJf6o cakH+QHwDszsoYvmrNq36MFGgvAHRjdlrHRBa4A1V1kzd4kOUokongcrOOgHY9yfglcvZqlJ qfa4l+1oxs1BvCi29psteQTtw+memmcGruKi+YHD7793zNCMtAtYidDmQ2pWaLfqSaryjlzR /3tBWMyvIeWZKURnZbBzWRREB7iWxEbZ014B3gICqZPDRwwitHpH8Om3eZr7ygZck6bBa4MU o1XgbZcspyCGqu1xF/bMAY2iCDcq6ULKQceuKkbeQ8qxvt9hVxJC2W3lHq8dlK1pkHPDg9wO JoAXek8MF37R8gpLoGWl41FIUb3hFiu3zhDDvslYM4BmzI18QgQTQnotJH8= In-Reply-To: <17bf8f85-9a9c-4d7d-add7-cd92313f73f1@suse.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit 在 2025/12/31 14:35, Qu Wenruo 写道: > > > 在 2025/12/31 13:59, Daniel J Blueman 写道: >> On Tue, 30 Dec 2025 at 17:28, Qu Wenruo wrote: >>> 在 2025/12/30 19:26, Qu Wenruo 写道: >>>> 在 2025/12/30 18:02, Daniel J Blueman 写道: >>>>> When mounting a BTRFS filesystem on 6.19-rc3 on ARM64 using xxhash >>>>> checksumming and KASAN, I see invalid access: >>>> >>>> Mind to share the page size? As aarch64 has 3 different supported pages >>>> size (4K, 16K, 64K). >>>> >>>> I'll give it a try on that branch. Although on my rc1 based development >>>> branch it looks OK so far. >>> >>> Tried both 4K and 64K page size with KASAN enabled, all on 6.19-rc3 tag, >>> no reproduce on newly created fs with xxhash. >>> >>> My environment is aarch64 VM on Orion O6 board. >>> >>> The xxhash implementation is the same xxhash64-generic: >>> >>> [   17.035933] BTRFS: device fsid 260364b9-d059-410c-92de-56243c346d6d >>> devid 1 transid 8 /dev/mapper/test-scratch1 (253:2) scanned by mount >>> (629) >>> [   17.038033] BTRFS info (device dm-2): first mount of filesystem >>> 260364b9-d059-410c-92de-56243c346d6d >>> [   17.038645] BTRFS info (device dm-2): using xxhash64 >>> (xxhash64-generic) checksum algorithm >>> [   17.041303] BTRFS info (device dm-2): checking UUID tree >>> [   17.041390] BTRFS info (device dm-2): turning on async discard >>> [   17.041393] BTRFS info (device dm-2): enabling free space tree >>> [   19.032109] BTRFS info (device dm-2): last unmount of filesystem >>> 260364b9-d059-410c-92de-56243c346d6d >>> >>> So there maybe something else involved, either related to the fs or the >>> hardware. >> >> Thanks for checking Wenruo! >> >> With KASAN_GENERIC or KASAN_HW_TAGS, I don't see "kasan: >> KernelAddressSanitizer initialized", so please ensure you are using >> KASAN_SW_TAGS, KASAN_OUTLINE and 4KB pages. Full config at >> https://gist.github.com/dblueman/cb4113f2cf880520081cf3f7c8dae13f > > Thanks a lot for the detailed configs. > > Unfortunately with that KASAN_SW_TAGS and KASAN_INLINE, the kernel can > no longer boot, will always crash at boot with the following call trace, > thus not even able to reach btrfs: > > [    3.938722] > ================================================================== > [    3.938739] BUG: KASAN: invalid-access in > bpf_patch_insn_data+0x178/0x3b0 [...] > > > Considering this is only showing up in KASAN_SW_TAGS, not HW_TAGS or the > default generic mode, I'm wondering if this is a bug in KASAN itself. > > Adding KASAN people to the thread, meanwhile I'll check more KASAN + > hardware combinations including x86_64 (since it's still 4K page size). I tried the following combinations, with a simple workload of mounting a btrfs with xxhash checksum. According to the original report, the KASAN is triggered as btrfs metadata verification time, thus mount option/workload shouldn't cause any different, as all metadata will use the same checksum algorithm. x86_64 + generic + inline: PASS x86_64 + generic + outline: PASS arm64 + soft tag + inline: KASAN error at boot arm64 + soft tag + outline: KASAN error at boot arm64 + hard tag: PASS arm64 + generic + inline: PASS arm64 + generic + outline: PASS So it looks like it's the software tag based KASAN itself causing false alerts. Thanks, Qu > > Thanks, > Qu > > >> >> Also ensure your mount options resolve similar to >> "rw,relatime,compress=zstd:3,ssd,discard=async,space_cache=v2,subvolid=5,subvol=/". >> >> Failing that, let me know of any significant filesystem differences from: >> # btrfs inspect-internal dump-super /dev/nvme0n1p5 >> superblock: bytenr=65536, device=/dev/nvme0n1p5 >> --------------------------------------------------------- >> csum_type        1 (xxhash64) >> csum_size        8 >> csum            0x97ec1a3695ae35d0 [match] >> bytenr            65536 >> flags            0x1 >>              ( WRITTEN ) >> magic            _BHRfS_M [match] >> fsid            f99f2753-0283-4f93-8f5d-7a9f59f148cc >> metadata_uuid        00000000-0000-0000-0000-000000000000 >> label >> generation        34305 >> root            586579968 >> sys_array_size        129 >> chunk_root_generation    33351 >> root_level        0 >> chunk_root        19357892608 >> chunk_root_level    0 >> log_root        0 >> log_root_transid (deprecated)    0 >> log_root_level        0 >> total_bytes        83886080000 >> bytes_used        14462930944 >> sectorsize        4096 >> nodesize        16384 >> leafsize (deprecated)    16384 >> stripesize        4096 >> root_dir        6 >> num_devices        1 >> compat_flags        0x0 >> compat_ro_flags        0x3 >>              ( FREE_SPACE_TREE | >>                FREE_SPACE_TREE_VALID ) >> incompat_flags        0x361 >>              ( MIXED_BACKREF | >>                BIG_METADATA | >>                EXTENDED_IREF | >>                SKINNY_METADATA | >>                NO_HOLES ) >> cache_generation    0 >> uuid_tree_generation    34305 >> dev_item.uuid        86166b5f-2258-4ab9-aac6-0d0e37ffbdb6 >> dev_item.fsid        f99f2753-0283-4f93-8f5d-7a9f59f148cc [match] >> dev_item.type        0 >> dev_item.total_bytes    83886080000 >> dev_item.bytes_used    22624075776 >> dev_item.io_align    4096 >> dev_item.io_width    4096 >> dev_item.sector_size    4096 >> dev_item.devid        1 >> dev_item.dev_group    0 >> dev_item.seek_speed    0 >> dev_item.bandwidth    0 >> dev_item.generation    0 >> >> Thanks, >>    Dan >> -- >> Daniel J Blueman > >