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).