From: Qu Wenruo wqu@suse.com
commit 6bf9e4bd6a277840d3fe8c5d5d530a1fbd3db592 upstream
[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: <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 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 jungyeon@gatech.edu Link: https://bugzilla.kernel.org/show_bug.cgi?id=202763 Reviewed-by: Nikolay Borisov nborisov@suse.com Signed-off-by: Qu Wenruo wqu@suse.com Signed-off-by: David Sterba dsterba@suse.com [sudip: use original btrfs_inode_type()] Signed-off-by: Sudip Mukherjee sudipm.mukherjee@gmail.com Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- fs/btrfs/inode.c | 41 +++++++++++++++++++++++++++++++++-------- fs/btrfs/tests/inode-tests.c | 1 + 2 files changed, 34 insertions(+), 8 deletions(-)
--- a/fs/btrfs/inode.c +++ b/fs/btrfs/inode.c @@ -5584,12 +5584,14 @@ no_delete: }
/* - * 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; @@ -5622,6 +5624,8 @@ static int btrfs_inode_by_name(struct in __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; @@ -5908,6 +5912,11 @@ static struct inode *new_simple_dir(stru 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); @@ -5915,18 +5924,31 @@ struct inode *btrfs_lookup_dentry(struct 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; }
@@ -6544,11 +6566,6 @@ fail: 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. @@ -7160,6 +7177,14 @@ again: 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);
--- a/fs/btrfs/tests/inode-tests.c +++ b/fs/btrfs/tests/inode-tests.c @@ -245,6 +245,7 @@ static noinline int test_btrfs_get_exten 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;