From 6bf9e4bd6a277840d3fe8c5d5d530a1fbd3db592 Mon Sep 17 00:00:00 2001 From: Qu Wenruo Date: Wed, 13 Mar 2019 13:55:11 +0800 Subject: [PATCH] btrfs: inode: Verify inode mode to avoid NULL pointer dereference [BUG] When accessing 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: 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 RIP: 0010:default_idle+0x1e/0x170 [CAUSE] The crafted image has a 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 symlink. 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 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 end_bio_extent_readpage() expects tree->ops populated, as it's reading regular data extent. This causes NULL pointer dereference. [FIX] This patch fixes the problem in two ways: - 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 accessed. - Verify inode mode when getting extent mapping Only regular file should have regular or preallocated extent. If we found regular/preallocated file extent for symlink or the rest, we error out before submitting the 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 Link: https://bugzilla.kernel.org/show_bug.cgi?id=202763 Reviewed-by: Nikolay Borisov Signed-off-by: Qu Wenruo Signed-off-by: David Sterba --- fs/btrfs/inode.c | 67 +++++++++++++++++++++++++----------- fs/btrfs/tests/inode-tests.c | 1 + 2 files changed, 47 insertions(+), 21 deletions(-) diff --git a/fs/btrfs/inode.c b/fs/btrfs/inode.c index 1d81a7a78a3f..baa80d808806 100644 --- a/fs/btrfs/inode.c +++ b/fs/btrfs/inode.c @@ -5437,12 +5437,14 @@ void btrfs_evict_inode(struct inode *inode) } /* - * this returns the key found in the dir entry in the location pointer. + * Return 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; @@ -5471,6 +5473,8 @@ 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; @@ -5708,6 +5712,24 @@ static struct inode *new_simple_dir(struct super_block *s, return inode; } +static inline u8 btrfs_inode_type(struct inode *inode) +{ + /* + * Compile-time asserts that generic FT_* types still match + * BTRFS_FT_* types + */ + BUILD_BUG_ON(BTRFS_FT_UNKNOWN != FT_UNKNOWN); + BUILD_BUG_ON(BTRFS_FT_REG_FILE != FT_REG_FILE); + BUILD_BUG_ON(BTRFS_FT_DIR != FT_DIR); + BUILD_BUG_ON(BTRFS_FT_CHRDEV != FT_CHRDEV); + BUILD_BUG_ON(BTRFS_FT_BLKDEV != FT_BLKDEV); + BUILD_BUG_ON(BTRFS_FT_FIFO != FT_FIFO); + BUILD_BUG_ON(BTRFS_FT_SOCK != FT_SOCK); + BUILD_BUG_ON(BTRFS_FT_SYMLINK != FT_SYMLINK); + + return fs_umode_to_ftype(inode->i_mode); +} + struct inode *btrfs_lookup_dentry(struct inode *dir, struct dentry *dentry) { struct btrfs_fs_info *fs_info = btrfs_sb(dir->i_sb); @@ -5715,18 +5737,31 @@ 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); + if (IS_ERR(inode)) + return inode; + + /* 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; } @@ -6327,24 +6362,6 @@ static struct inode *btrfs_new_inode(struct btrfs_trans_handle *trans, return ERR_PTR(ret); } -static inline u8 btrfs_inode_type(struct inode *inode) -{ - /* - * Compile-time asserts that generic FT_* types still match - * BTRFS_FT_* types - */ - BUILD_BUG_ON(BTRFS_FT_UNKNOWN != FT_UNKNOWN); - BUILD_BUG_ON(BTRFS_FT_REG_FILE != FT_REG_FILE); - BUILD_BUG_ON(BTRFS_FT_DIR != FT_DIR); - BUILD_BUG_ON(BTRFS_FT_CHRDEV != FT_CHRDEV); - BUILD_BUG_ON(BTRFS_FT_BLKDEV != FT_BLKDEV); - BUILD_BUG_ON(BTRFS_FT_FIFO != FT_FIFO); - BUILD_BUG_ON(BTRFS_FT_SOCK != FT_SOCK); - BUILD_BUG_ON(BTRFS_FT_SYMLINK != FT_SYMLINK); - - return fs_umode_to_ftype(inode->i_mode); -} - /* * utility function to add 'inode' into 'parent_inode' with * a give name and a given sequence number. @@ -6862,6 +6879,14 @@ struct extent_map *btrfs_get_extent(struct btrfs_inode *inode, extent_start = found_key.offset; if (extent_type == BTRFS_FILE_EXTENT_REG || extent_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 3d2c7abda5de..bc6dbd1b42fd 100644 --- a/fs/btrfs/tests/inode-tests.c +++ b/fs/btrfs/tests/inode-tests.c @@ -234,6 +234,7 @@ 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;