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 <jungyeon@xxxxxxxxxx> > Link: https://bugzilla.kernel.org/show_bug.cgi?id=202691 > Signed-off-by: Qu Wenruo <wqu@xxxxxxxx> I had already reviewed the earlier posting of this patch so: Reviewed-by: Nikolay Borisov <nborisov@xxxxxxxx> > --- > 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). >
