On 13.03.19 г. 10:55 ч., Qu Wenruo wrote:
> [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 <[email protected]>
> Link: https://bugzilla.kernel.org/show_bug.cgi?id=202691
> Signed-off-by: Qu Wenruo <[email protected]>
I had already reviewed the earlier posting of this patch so:
Reviewed-by: Nikolay Borisov <[email protected]>
> ---
> fs/btrfs/tree-checker.c | 84 +++++++++++++++++++++++++++++++++++++++++
> fs/btrfs/volumes.c | 9 -----
> fs/btrfs/volumes.h | 9 +++++
> 3 files changed, 93 insertions(+), 9 deletions(-)
>
> diff --git a/fs/btrfs/tree-checker.c b/fs/btrfs/tree-checker.c
> index fe3f37c23c29..5ccb4be583ea 100644
> --- a/fs/btrfs/tree-checker.c
> +++ b/fs/btrfs/tree-checker.c
> @@ -594,6 +594,87 @@ int btrfs_check_chunk_valid(struct btrfs_fs_info
> *fs_info,
> 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);
> + goto error;
> + }
> + if (key->offset > max_devid) {
> + dev_item_err(fs_info, leaf, slot,
> + "invalid devid: has=%llu expect=[0, %llu]",
> + key->offset, max_devid);
> + goto error;
> + }
> + 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));
> + goto error;
> + }
> +
> + /*
> + * Since btrfs device add doesn't check device size at all, we could
> + * have device item whose size is smaller than 1M which is useless, but
> + * still valid.
> + * So here we can only check the obviously wrong case.
> + */
> + if (btrfs_device_total_bytes(leaf, ditem) == 0) {
> + dev_item_err(fs_info, leaf, slot,
> + "invalid total bytes: have 0");
> + goto error;
> + }
> + 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));
> + goto error;
> + }
> + /*
> + * Remaining members like io_align/type/gen/dev_group aren't really
> + * utilized.
> + * Skip them to make later usage of them easier.
> + */
> + return 0;
> +error:
> + return -EUCLEAN;
> +}
> +
> /*
> * Common point to switch the item-specific validation.
> */
> @@ -624,6 +705,9 @@ static int check_leaf_item(struct btrfs_fs_info *fs_info,
> 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;
> }
> diff --git a/fs/btrfs/volumes.c b/fs/btrfs/volumes.c
> index 0e3822870f1e..0b839ecbe73f 100644
> --- a/fs/btrfs/volumes.c
> +++ b/fs/btrfs/volumes.c
> @@ -4964,15 +4964,6 @@ static void check_raid56_incompat_flag(struct
> btrfs_fs_info *info, u64 type)
> 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)
> {
> diff --git a/fs/btrfs/volumes.h b/fs/btrfs/volumes.h
> index ed806649a473..481c012eae79 100644
> --- a/fs/btrfs/volumes.h
> +++ b/fs/btrfs/volumes.h
> @@ -258,6 +258,15 @@ 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).
>
