On 13.03.19 г. 10:55 ч., Qu Wenruo wrote: > [BUG] > When access a file on a crafted image, btrfs can crash in block layer: > > BUG: unable to handle kernel NULL pointer dereference at 0000000000000008 > PGD 136501067 P4D 136501067 PUD 124519067 PMD 0 > CPU: 3 PID: 0 Comm: swapper/3 Not tainted 5.0.0-rc8-default #252 > RIP: 0010:end_bio_extent_readpage+0x144/0x700 > Call Trace: > <IRQ> > blk_update_request+0x8f/0x350 > blk_mq_end_request+0x1a/0x120 > blk_done_softirq+0x99/0xc0 > __do_softirq+0xc7/0x467 > irq_exit+0xd1/0xe0 > call_function_single_interrupt+0xf/0x20 > </IRQ> > RIP: 0010:default_idle+0x1e/0x170 > > [CAUSE] > The crafted image has a pretty tricky corruption, the INODE_ITEM has a > different type against its parent dir: > item 20 key (268 INODE_ITEM 0) itemoff 2808 itemsize 160 > generation 13 transid 13 size 1048576 nbytes 1048576 > block group 0 mode 121644 links 1 uid 0 gid 0 rdev 0 > sequence 9 flags 0x0(none) > > This mode number 0120000 means it's a soft link. > > But the dir item think it's still a regular file: > item 8 key (264 DIR_INDEX 5) itemoff 3707 itemsize 32 > location key (268 INODE_ITEM 0) type FILE > transid 13 data_len 0 name_len 2 > name: f4 > item 40 key (264 DIR_ITEM 51821248) itemoff 1573 itemsize 32 > location key (268 INODE_ITEM 0) type FILE > transid 13 data_len 0 name_len 2 > name: f4 > > For btrfs symlink, we don't set BTRFS_I(inode)->io_tree.ops and leave > it empty, as symlink is only designed to have inlined extent, all > handled by tree block read. > Thus no need to trigger btrfs_submit_bio_hook() for inline file extent. > > However for end_bio_extent_readpage() it expects tree->ops populated, as > it's reading regular data extent. > This causes NULL pointer dereference. > > [FIX] > This patch fixes the problem by 2 directions: > - Verify inode mode against its dir item when looking up inode > So in btrfs_lookup_dentry() if we find inode mode mismatch with dir > item, we error out so that corrupted inode will not be access. > > - Verify inode mode when getting extent mapping > Only regular file should have regular or preallocated extent. > If we found regular/preallocated file extent for soft link or > whatever, we error out before we submit read bio. > > With this fix that crafted image can be rejected gracefully: > BTRFS critical (device loop0): inode mode mismatch with dir: inode mode=0121644 btrfs type=7 dir type=1 > > Reported-by: Yoon Jungyeon <jungyeon@xxxxxxxxxx> > Link: https://bugzilla.kernel.org/show_bug.cgi?id=202763 > Signed-off-by: Qu Wenruo <wqu@xxxxxxxx> Reviewed-by: Nikolay Borisov <nborisov@xxxxxxxx> > --- > fs/btrfs/inode.c | 38 ++++++++++++++++++++++++++++-------- > fs/btrfs/tests/inode-tests.c | 1 + > 2 files changed, 31 insertions(+), 8 deletions(-) > > diff --git a/fs/btrfs/inode.c b/fs/btrfs/inode.c > index 5c349667c761..4ced641aaa8e 100644 > --- a/fs/btrfs/inode.c > +++ b/fs/btrfs/inode.c > @@ -5396,12 +5396,13 @@ void btrfs_evict_inode(struct inode *inode) > } > > /* > - * this returns the key found in the dir entry in the location pointer. > + * this returns the key found in the dir entry in the location pointer, > + * fill @type with BTRFS_FT_*, and return 0. > * If no dir entries were found, returns -ENOENT. > * If found a corrupted location in dir entry, returns -EUCLEAN. > */ > static int btrfs_inode_by_name(struct inode *dir, struct dentry *dentry, > - struct btrfs_key *location) > + struct btrfs_key *location, u8 *type) > { > const char *name = dentry->d_name.name; > int namelen = dentry->d_name.len; > @@ -5430,6 +5431,8 @@ static int btrfs_inode_by_name(struct inode *dir, struct dentry *dentry, > __func__, name, btrfs_ino(BTRFS_I(dir)), > location->objectid, location->type, location->offset); > } > + if (!ret) > + *type = btrfs_dir_type(path->nodes[0], di); > out: > btrfs_free_path(path); > return ret; > @@ -5667,6 +5670,11 @@ static struct inode *new_simple_dir(struct super_block *s, > return inode; > } > > +static inline u8 btrfs_inode_type(struct inode *inode) > +{ > + return btrfs_type_by_mode[(inode->i_mode & S_IFMT) >> S_SHIFT]; > +} > + > struct inode *btrfs_lookup_dentry(struct inode *dir, struct dentry *dentry) > { > struct btrfs_fs_info *fs_info = btrfs_sb(dir->i_sb); > @@ -5674,18 +5682,29 @@ struct inode *btrfs_lookup_dentry(struct inode *dir, struct dentry *dentry) > struct btrfs_root *root = BTRFS_I(dir)->root; > struct btrfs_root *sub_root = root; > struct btrfs_key location; > + u8 di_type = 0; > int index; > int ret = 0; > > if (dentry->d_name.len > BTRFS_NAME_LEN) > return ERR_PTR(-ENAMETOOLONG); > > - ret = btrfs_inode_by_name(dir, dentry, &location); > + ret = btrfs_inode_by_name(dir, dentry, &location, &di_type); > if (ret < 0) > return ERR_PTR(ret); > > if (location.type == BTRFS_INODE_ITEM_KEY) { > inode = btrfs_iget(dir->i_sb, &location, root, NULL); > + > + /* Do extra check against inode mode with di_type */ > + if (btrfs_inode_type(inode) != di_type) { > + btrfs_crit(fs_info, > +"inode mode mismatch with dir: inode mode=0%o btrfs type=%u dir type=%u", > + inode->i_mode, btrfs_inode_type(inode), > + di_type); > + iput(inode); > + return ERR_PTR(-EUCLEAN); > + } > return inode; > } > > @@ -6290,11 +6309,6 @@ static struct inode *btrfs_new_inode(struct btrfs_trans_handle *trans, > return ERR_PTR(ret); > } > > -static inline u8 btrfs_inode_type(struct inode *inode) > -{ > - return btrfs_type_by_mode[(inode->i_mode & S_IFMT) >> S_SHIFT]; > -} > - > /* > * utility function to add 'inode' into 'parent_inode' with > * a give name and a given sequence number. > @@ -6816,6 +6830,14 @@ struct extent_map *btrfs_get_extent(struct btrfs_inode *inode, > extent_start = found_key.offset; > if (found_type == BTRFS_FILE_EXTENT_REG || > found_type == BTRFS_FILE_EXTENT_PREALLOC) { > + /* Only regular file could have regular/prealloc extent */ > + if (!S_ISREG(inode->vfs_inode.i_mode)) { > + ret = -EUCLEAN; > + btrfs_crit(fs_info, > + "regular/prealloc extent found for non-regular inode %llu", > + btrfs_ino(inode)); > + goto out; > + } > extent_end = extent_start + > btrfs_file_extent_num_bytes(leaf, item); > > diff --git a/fs/btrfs/tests/inode-tests.c b/fs/btrfs/tests/inode-tests.c > index af0c8e30d9e2..b01dbcab9eed 100644 > --- a/fs/btrfs/tests/inode-tests.c > +++ b/fs/btrfs/tests/inode-tests.c > @@ -232,6 +232,7 @@ static noinline int test_btrfs_get_extent(u32 sectorsize, u32 nodesize) > return ret; > } > > + inode->i_mode = S_IFREG; > BTRFS_I(inode)->location.type = BTRFS_INODE_ITEM_KEY; > BTRFS_I(inode)->location.objectid = BTRFS_FIRST_FREE_OBJECTID; > BTRFS_I(inode)->location.offset = 0; >
