[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 <[email protected]>
Link: https://bugzilla.kernel.org/show_bug.cgi?id=202763
Signed-off-by: Qu Wenruo <[email protected]>
---
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;
--
2.21.0
