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[2403:580d:fda1:0:2bb5:f164:6e6a:38d8]) by smtp.gmail.com with ESMTPSA id d2e1a72fcca58-83965c30ddasm24549775b3a.21.2026.05.11.01.40.15 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Mon, 11 May 2026 01:40:17 -0700 (PDT) Message-ID: Date: Mon, 11 May 2026 18:10:12 +0930 Precedence: bulk X-Mailing-List: linux-btrfs@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v4] btrfs: validate root ref names in tree-checker To: Zhang Cen , Chris Mason , David Sterba Cc: linux-btrfs@vger.kernel.org, zerocling0077@gmail.com, 2045gemini@gmail.com References: <20260511070128.2093775-1-rollkingzzc@gmail.com> Content-Language: en-US From: Qu Wenruo 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: <20260511070128.2093775-1-rollkingzzc@gmail.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit 在 2026/5/11 16:31, Zhang Cen 写道: > ROOT_REF and ROOT_BACKREF items contain a struct btrfs_root_ref followed > by the subvolume name. Several readers assume that this layout is already > valid and then use the on-disk name length directly. A corrupted item can > therefore make those readers address bytes outside the item, and > BTRFS_IOC_GET_SUBVOL_INFO can copy too many bytes into its fixed-size UAPI > name buffer. > > Validate ROOT_REF and ROOT_BACKREF items in tree-checker before any reader > uses them. Reject records that do not contain a non-empty name, whose > name_len does not exactly describe the remaining item payload, or whose > name exceeds BTRFS_NAME_LEN. > > For BTRFS_IOC_GET_SUBVOL_INFO, copy only the validated on-disk name_len > instead of deriving the copy length from the item size. The ioctl result is > zeroed when allocated. That leaves the existing trailing zero byte > untouched. > > Signed-off-by: Zhang Cen Reviewed-by: Qu Wenruo Will run a full test before merge. Thanks, Qu > --- > fs/btrfs/ioctl.c | 12 ++++++------ > fs/btrfs/tree-checker.c | 36 ++++++++++++++++++++++++++++++++++++ > 2 files changed, 42 insertions(+), 6 deletions(-) > > diff --git a/fs/btrfs/ioctl.c b/fs/btrfs/ioctl.c > index a39460bf6..5958aa8c7 100644 > --- a/fs/btrfs/ioctl.c > +++ b/fs/btrfs/ioctl.c > @@ -1956,7 +1956,6 @@ static int btrfs_ioctl_get_subvol_info(struct inode *inode, void __user *argp) > struct btrfs_root_ref *rref; > struct extent_buffer *leaf; > unsigned long item_off; > - unsigned long item_len; > int slot; > int ret = 0; > > @@ -2031,17 +2030,18 @@ static int btrfs_ioctl_get_subvol_info(struct inode *inode, void __user *argp) > btrfs_item_key_to_cpu(leaf, &key, slot); > if (key.objectid == subvol_info->treeid && > key.type == BTRFS_ROOT_BACKREF_KEY) { > + u16 name_len; > + > subvol_info->parent_id = key.offset; > > rref = btrfs_item_ptr(leaf, slot, struct btrfs_root_ref); > + name_len = btrfs_root_ref_name_len(leaf, rref); > subvol_info->dirid = btrfs_root_ref_dirid(leaf, rref); > > - item_off = btrfs_item_ptr_offset(leaf, slot) > - + sizeof(struct btrfs_root_ref); > - item_len = btrfs_item_size(leaf, slot) > - - sizeof(struct btrfs_root_ref); > + item_off = btrfs_item_ptr_offset(leaf, slot) + > + sizeof(*rref); > read_extent_buffer(leaf, subvol_info->name, > - item_off, item_len); > + item_off, name_len); > } else { > ret = -ENOENT; > goto out; > diff --git a/fs/btrfs/tree-checker.c b/fs/btrfs/tree-checker.c > index 1f15d0793..b48520ff0 100644 > --- a/fs/btrfs/tree-checker.c > +++ b/fs/btrfs/tree-checker.c > @@ -1371,6 +1371,38 @@ static int check_root_item(struct extent_buffer *leaf, struct btrfs_key *key, > return 0; > } > > +static int check_root_ref(struct extent_buffer *leaf, struct btrfs_key *key, > + int slot) > +{ > + struct btrfs_root_ref *rref; > + u32 item_size = btrfs_item_size(leaf, slot); > + u32 name_len; > + > + if (unlikely(item_size <= sizeof(*rref))) { > + generic_err(leaf, slot, > + "invalid root ref item size for key type %u, have %u expect > %zu", > + key->type, item_size, sizeof(*rref)); > + return -EUCLEAN; > + } > + > + rref = btrfs_item_ptr(leaf, slot, struct btrfs_root_ref); > + name_len = btrfs_root_ref_name_len(leaf, rref); > + if (unlikely(name_len > BTRFS_NAME_LEN)) { > + generic_err(leaf, slot, > + "root ref name too long for key type %u, have %u max %u", > + key->type, name_len, BTRFS_NAME_LEN); > + return -EUCLEAN; > + } > + if (unlikely(item_size != sizeof(*rref) + name_len)) { > + generic_err(leaf, slot, > + "invalid root ref item size for key type %u, have %u expect %zu", > + key->type, item_size, sizeof(*rref) + name_len); > + return -EUCLEAN; > + } > + > + return 0; > +} > + > __printf(3,4) > __cold > static void extent_err(const struct extent_buffer *eb, int slot, > @@ -2226,6 +2258,10 @@ static enum btrfs_tree_block_status check_leaf_item(struct extent_buffer *leaf, > case BTRFS_ROOT_ITEM_KEY: > ret = check_root_item(leaf, key, slot); > break; > + case BTRFS_ROOT_REF_KEY: > + case BTRFS_ROOT_BACKREF_KEY: > + ret = check_root_ref(leaf, key, slot); > + break; > case BTRFS_EXTENT_ITEM_KEY: > case BTRFS_METADATA_ITEM_KEY: > ret = check_extent_item(leaf, key, slot, prev_key);