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    Subject[PATCH 4.19 26/71] btrfs: tree-checker: Verify dev item
    Date
    From: Qu Wenruo <wqu@suse.com>

    commit ab4ba2e133463c702b37242560d7fabedd2dc750 upstream.

    [BUG]
    For fuzzed image whose DEV_ITEM has invalid total_bytes as 0, then
    kernel will just panic:
    BUG: unable to handle kernel NULL pointer dereference at 0000000000000098
    #PF error: [normal kernel read fault]
    PGD 800000022b2bd067 P4D 800000022b2bd067 PUD 22b2bc067 PMD 0
    Oops: 0000 [#1] SMP PTI
    CPU: 0 PID: 1106 Comm: mount Not tainted 5.0.0-rc8+ #9
    RIP: 0010:btrfs_verify_dev_extents+0x2a5/0x5a0
    Call Trace:
    open_ctree+0x160d/0x2149
    btrfs_mount_root+0x5b2/0x680

    [CAUSE]
    If device extent verification finds a deivce with 0 total_bytes, then it
    assumes it's a seed dummy, then search for seed devices.

    But in this case, there is no seed device at all, causing NULL pointer.

    [FIX]
    Since this is caused by fuzzed image, let's go the tree-check way, just
    add a new verification for device item.

    Reported-by: Yoon Jungyeon <jungyeon@gatech.edu>
    Link: https://bugzilla.kernel.org/show_bug.cgi?id=202691
    Reviewed-by: Nikolay Borisov <nborisov@suse.com>
    Signed-off-by: Qu Wenruo <wqu@suse.com>
    Reviewed-by: Johannes Thumshirn <jthumshirn@suse.de>
    Signed-off-by: David Sterba <dsterba@suse.com>
    Signed-off-by: Ben Hutchings <ben.hutchings@codethink.co.uk>
    Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
    ---
    fs/btrfs/tree-checker.c | 74 ++++++++++++++++++++++++++++++++++++++++++++++++
    fs/btrfs/volumes.c | 9 -----
    fs/btrfs/volumes.h | 9 +++++
    3 files changed, 83 insertions(+), 9 deletions(-)

    --- a/fs/btrfs/tree-checker.c
    +++ b/fs/btrfs/tree-checker.c
    @@ -600,6 +600,77 @@ int btrfs_check_chunk_valid(struct btrfs
    return 0;
    }

    +__printf(4, 5)
    +__cold
    +static void dev_item_err(const struct btrfs_fs_info *fs_info,
    + const struct extent_buffer *eb, int slot,
    + const char *fmt, ...)
    +{
    + struct btrfs_key key;
    + struct va_format vaf;
    + va_list args;
    +
    + btrfs_item_key_to_cpu(eb, &key, slot);
    + va_start(args, fmt);
    +
    + vaf.fmt = fmt;
    + vaf.va = &args;
    +
    + btrfs_crit(fs_info,
    + "corrupt %s: root=%llu block=%llu slot=%d devid=%llu %pV",
    + btrfs_header_level(eb) == 0 ? "leaf" : "node",
    + btrfs_header_owner(eb), btrfs_header_bytenr(eb), slot,
    + key.objectid, &vaf);
    + va_end(args);
    +}
    +
    +static int check_dev_item(struct btrfs_fs_info *fs_info,
    + struct extent_buffer *leaf,
    + struct btrfs_key *key, int slot)
    +{
    + struct btrfs_dev_item *ditem;
    + u64 max_devid = max(BTRFS_MAX_DEVS(fs_info), BTRFS_MAX_DEVS_SYS_CHUNK);
    +
    + if (key->objectid != BTRFS_DEV_ITEMS_OBJECTID) {
    + dev_item_err(fs_info, leaf, slot,
    + "invalid objectid: has=%llu expect=%llu",
    + key->objectid, BTRFS_DEV_ITEMS_OBJECTID);
    + return -EUCLEAN;
    + }
    + if (key->offset > max_devid) {
    + dev_item_err(fs_info, leaf, slot,
    + "invalid devid: has=%llu expect=[0, %llu]",
    + key->offset, max_devid);
    + return -EUCLEAN;
    + }
    + ditem = btrfs_item_ptr(leaf, slot, struct btrfs_dev_item);
    + if (btrfs_device_id(leaf, ditem) != key->offset) {
    + dev_item_err(fs_info, leaf, slot,
    + "devid mismatch: key has=%llu item has=%llu",
    + key->offset, btrfs_device_id(leaf, ditem));
    + return -EUCLEAN;
    + }
    +
    + /*
    + * For device total_bytes, we don't have reliable way to check it, as
    + * it can be 0 for device removal. Device size check can only be done
    + * by dev extents check.
    + */
    + if (btrfs_device_bytes_used(leaf, ditem) >
    + btrfs_device_total_bytes(leaf, ditem)) {
    + dev_item_err(fs_info, leaf, slot,
    + "invalid bytes used: have %llu expect [0, %llu]",
    + btrfs_device_bytes_used(leaf, ditem),
    + btrfs_device_total_bytes(leaf, ditem));
    + return -EUCLEAN;
    + }
    + /*
    + * Remaining members like io_align/type/gen/dev_group aren't really
    + * utilized. Skip them to make later usage of them easier.
    + */
    + return 0;
    +}
    +
    /*
    * Common point to switch the item-specific validation.
    */
    @@ -630,6 +701,9 @@ static int check_leaf_item(struct btrfs_
    ret = btrfs_check_chunk_valid(fs_info, leaf, chunk,
    key->offset);
    break;
    + case BTRFS_DEV_ITEM_KEY:
    + ret = check_dev_item(fs_info, leaf, key, slot);
    + break;
    }
    return ret;
    }
    --- a/fs/btrfs/volumes.c
    +++ b/fs/btrfs/volumes.c
    @@ -4606,15 +4606,6 @@ static void check_raid56_incompat_flag(s
    btrfs_set_fs_incompat(info, RAID56);
    }

    -#define BTRFS_MAX_DEVS(info) ((BTRFS_MAX_ITEM_SIZE(info) \
    - - sizeof(struct btrfs_chunk)) \
    - / sizeof(struct btrfs_stripe) + 1)
    -
    -#define BTRFS_MAX_DEVS_SYS_CHUNK ((BTRFS_SYSTEM_CHUNK_ARRAY_SIZE \
    - - 2 * sizeof(struct btrfs_disk_key) \
    - - 2 * sizeof(struct btrfs_chunk)) \
    - / sizeof(struct btrfs_stripe) + 1)
    -
    static int __btrfs_alloc_chunk(struct btrfs_trans_handle *trans,
    u64 start, u64 type)
    {
    --- a/fs/btrfs/volumes.h
    +++ b/fs/btrfs/volumes.h
    @@ -257,6 +257,15 @@ struct btrfs_fs_devices {

    #define BTRFS_BIO_INLINE_CSUM_SIZE 64

    +#define BTRFS_MAX_DEVS(info) ((BTRFS_MAX_ITEM_SIZE(info) \
    + - sizeof(struct btrfs_chunk)) \
    + / sizeof(struct btrfs_stripe) + 1)
    +
    +#define BTRFS_MAX_DEVS_SYS_CHUNK ((BTRFS_SYSTEM_CHUNK_ARRAY_SIZE \
    + - 2 * sizeof(struct btrfs_disk_key) \
    + - 2 * sizeof(struct btrfs_chunk)) \
    + / sizeof(struct btrfs_stripe) + 1)
    +
    /*
    * we need the mirror number and stripe index to be passed around
    * the call chain while we are processing end_io (especially errors).

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