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[2403:580d:fda1::299]) by smtp.gmail.com with ESMTPSA id 98e67ed59e1d1-36490a7476csm340649a91.2.2026.04.27.17.44.43 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Mon, 27 Apr 2026 17:44:45 -0700 (PDT) Message-ID: <4fed7e18-4bc7-43a5-8438-62bff279fbe7@suse.com> Date: Tue, 28 Apr 2026 10:14:40 +0930 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 v3] btrfs: validate data reloc tree file extent item members in tree-checker From: Qu Wenruo To: Teng Liu <27rabbitlt@gmail.com>, linux-btrfs@vger.kernel.org Cc: dsterba@suse.com, clm@fb.com, linux-kernel@vger.kernel.org, syzbot+3e20d8f3d41bac5dc9a2@syzkaller.appspotmail.com References: <20260426201605.36626-1-27rabbitlt@gmail.com> <20260427202822.278326-1-27rabbitlt@gmail.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: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit 在 2026/4/28 07:45, Qu Wenruo 写道: > > > 在 2026/4/28 05:54, Teng Liu 写道: >> get_new_location() uses BUG_ON() to crash the kernel if the file extent >> item it looks up has any of offset, compression, encryption, or >> other_encoding set. The data reloc inode is only written by relocation's >> own paths -- insert_prealloc_file_extent() and >> insert_ordered_extent_file_extent() -- which always leave those four >> fields at 0 (the data reloc inode is created with BTRFS_INODE_NOCOMPRESS, >> and encryption/other_encoding are reserved-and-zero). Observing a >> non-zero value therefore means the leaf decoded from disk does not match >> what the kernel wrote, i.e. on-disk corruption. A malformed image can >> reach this code via balance and panic the kernel. >> >> Move the validation into tree-checker's check_extent_data_item(), where >> the constraint is enforced when the leaf is read off disk rather than >> after relocation has already started. The data reloc tree has a fixed >> root id (BTRFS_DATA_RELOC_TREE_OBJECTID) recorded in the extent buffer >> header, so check_extent_data_item() has all the information it needs to >> apply this check on its own. Report violations via file_extent_err() and >> print the four offending values. >> >> In get_new_location() replace the BUG_ON() with an ASSERT(). >> The caller in replace_file_extents() already handles non-zero returns >> from >> get_new_location() by breaking out of the loop without aborting the >> transaction, so no caller changes are needed. >> >> Suggested-by: Qu Wenruo >> Suggested-by: David Sterba >> Reported-by: syzbot+3e20d8f3d41bac5dc9a2@syzkaller.appspotmail.com >> Closes: https://syzkaller.appspot.com/bug?extid=3e20d8f3d41bac5dc9a2 >> Signed-off-by: Teng Liu <27rabbitlt@gmail.com> > > Reviewed-by: Qu Wenruo > > And merged. Unfortunately this tree-checker got triggered during btrfs/061 runs at write-time tree-checker, with arm64 64K page size. The offending file extent is as the following: [ 536.885066] item 69 key (258 EXTENT_DATA 4063232) itemoff 12400 itemsize 53 [ 536.885067] generation 28 type 1 [ 536.885067] extent data disk bytenr 10512723968 nr 36864 [ 536.885068] extent data offset 24576 nr 12288 ram 36864 [ 536.885069] extent compression 0 Note the offset is not zero, and the type is 1 which means it's a regular file extent. So the check is causing false alerts. Now the patch is reverted, and I'll spend more time digging into the case. Thanks, Qu > > Thanks, > Qu > >> --- >> Changes in v3: >>   - Move the corruption check from relocation.c into tree-checker's >>     check_extent_data_item(), per Qu and David. The data reloc tree's >>     fixed objectid is recorded in the extent buffer header, so the >>     check has all the context it needs at read time. >>   - Use file_extent_err() and print offset/compression/encryption/ >>     other_encoding values, per Qu. >>   - Replace the BUG_ON in get_new_location() with ASSERT() rather than >>     -EUCLEAN, per David. >> >> Changes in v2: >>   - Pair the -EUCLEAN return with btrfs_print_leaf() and btrfs_err() so >>     the offending leaf is dumped to dmesg, per Qu's review of v1. >>   - Expand the changelog to argue why non-zero >>     compression/encryption/other_encoding in the data reloc inode imply >>     on-disk corruption. >> >>   fs/btrfs/relocation.c   |  8 ++++---- >>   fs/btrfs/tree-checker.c | 21 +++++++++++++++++++++ >>   2 files changed, 25 insertions(+), 4 deletions(-) >> >> diff --git a/fs/btrfs/relocation.c b/fs/btrfs/relocation.c >> index 1c42c5180bdd..527d4dbfe31c 100644 >> --- a/fs/btrfs/relocation.c >> +++ b/fs/btrfs/relocation.c >> @@ -835,10 +835,10 @@ static int get_new_location(struct inode >> *reloc_inode, u64 *new_bytenr, >>       fi = btrfs_item_ptr(leaf, path->slots[0], >>                   struct btrfs_file_extent_item); >> -    BUG_ON(btrfs_file_extent_offset(leaf, fi) || >> -           btrfs_file_extent_compression(leaf, fi) || >> -           btrfs_file_extent_encryption(leaf, fi) || >> -           btrfs_file_extent_other_encoding(leaf, fi)); >> +    ASSERT(!btrfs_file_extent_offset(leaf, fi) && >> +           !btrfs_file_extent_compression(leaf, fi) && >> +           !btrfs_file_extent_encryption(leaf, fi) && >> +           !btrfs_file_extent_other_encoding(leaf, fi)); >>       if (num_bytes != btrfs_file_extent_disk_num_bytes(leaf, fi)) >>           return -EINVAL; >> diff --git a/fs/btrfs/tree-checker.c b/fs/btrfs/tree-checker.c >> index 1f15d0793a9c..e4864f7a471e 100644 >> --- a/fs/btrfs/tree-checker.c >> +++ b/fs/btrfs/tree-checker.c >> @@ -296,6 +296,27 @@ static int check_extent_data_item(struct >> extent_buffer *leaf, >>           return 0; >>       } >> +    /* >> +     * For the data reloc tree, file extent items are written by >> +     * relocation's own paths, which always leave offset, compression, >> +     * encryption and other_encoding as 0. Any non-zero value here means >> +     * the leaf decoded from disk does not match what the kernel wrote, >> +     * i.e. on-disk corruption. >> +     */ >> +    if (unlikely(btrfs_header_owner(leaf) == >> BTRFS_DATA_RELOC_TREE_OBJECTID && >> +             (btrfs_file_extent_offset(leaf, fi) || >> +              btrfs_file_extent_compression(leaf, fi) || >> +              btrfs_file_extent_encryption(leaf, fi) || >> +              btrfs_file_extent_other_encoding(leaf, fi)))) { >> +        file_extent_err(leaf, slot, >> +"invalid members for data reloc tree, offset=%llu compress=%u >> encryption=%u other_encoding=%u", >> +                btrfs_file_extent_offset(leaf, fi), >> +                btrfs_file_extent_compression(leaf, fi), >> +                btrfs_file_extent_encryption(leaf, fi), >> +                btrfs_file_extent_other_encoding(leaf, fi)); >> +        return -EUCLEAN; >> +    } >> + >>       /* Regular or preallocated extent has fixed item size */ >>       if (unlikely(item_size != sizeof(*fi))) { >>           file_extent_err(leaf, slot, > >