btrfs-progs: check: Avoid reading beyond item boundary for inode_ref

When reading out name from inode_ref, it's possible that corrupted
name_len can lead to read beyond boundary of item or even extent buffer.

This happens when checking fuzzed image /tmp/bko-161811.raw, for both
lowmem mode and original mode.

ERROR: root 5 INODE REF[256 256] doesn't have related DIR_INDEX[256 504403158265495680] namelen 0 filename  filetype 0
ERROR: root 5 INODE REF[256 256] doesn't have related DIR_ITEM[256 4294967294] namelen 0 filename  filetype 0
WARNING: root 5 INODE_REF[256 256] name too long
==13022== Invalid read of size 8
==13022==    at 0x4C319BE: memmove (in /usr/lib/valgrind/vgpreload_memcheck-amd64-linux.so)
==13022==    by 0x431518: read_extent_buffer (extent_io.c:863)
==13022==    by 0x474730: check_inode_ref (cmds-check.c:4307)
==13022==    by 0x475D65: check_inode_item (cmds-check.c:4890)
==13022==    by 0x476200: check_fs_first_inode (cmds-check.c:5011)
==13022==    by 0x476276: check_fs_root_v2 (cmds-check.c:5044)
==13022==    by 0x4769FB: check_fs_roots_v2 (cmds-check.c:5242)
==13022==    by 0x488B5B: cmd_check (cmds-check.c:13033)
==13022==    by 0x40A8C5: main (btrfs.c:246)
==13022==  Address 0x5c96780 is 0 bytes after a block of size 4,224 alloc'd
==13022==    at 0x4C2CF35: calloc (in /usr/lib/valgrind/vgpreload_memcheck-amd64-linux.so)
==13022==    by 0x4307E0: __alloc_extent_buffer (extent_io.c:538)
==13022==    by 0x430C37: alloc_extent_buffer (extent_io.c:642)
==13022==    by 0x413DFE: btrfs_find_create_tree_block (disk-io.c:193)
==13022==    by 0x414370: read_tree_block_fs_info (disk-io.c:340)
==13022==    by 0x40B5D5: read_tree_block (disk-io.h:125)
==13022==    by 0x40CFD2: read_node_slot (ctree.c:652)
==13022==    by 0x40E5EB: btrfs_search_slot (ctree.c:1172)
==13022==    by 0x4761A8: check_fs_first_inode (cmds-check.c:5001)
==13022==    by 0x476276: check_fs_root_v2 (cmds-check.c:5044)
==13022==    by 0x4769FB: check_fs_roots_v2 (cmds-check.c:5242)
==13022==    by 0x488B5B: cmd_check (cmds-check.c:13033)
=

Fix it by double checking inode_ref, name_len against item boundary
before trying to read out name from extent buffer, for both original
mode and lowmem mode.

Signed-off-by: Qu Wenruo <quwenruo@cn.fujitsu.com>
Signed-off-by: David Sterba <dsterba@suse.com>

diff --git a/cmds-check.c b/cmds-check.c
index 6b00201..071af53 100644 (file)
--- a/cmds-check.c
+++ b/cmds-check.c
@@ -1569,13 +1569,22 @@ static int process_inode_ref(struct extent_buffer *eb,
        while (cur < total) {
                name_len = btrfs_inode_ref_name_len(eb, ref);
                index = btrfs_inode_ref_index(eb, ref);
-               if (name_len <= BTRFS_NAME_LEN) {
+
+               /* inode_ref + namelen should not cross item boundary */
+               if (cur + sizeof(*ref) + name_len > total ||
+                   name_len > BTRFS_NAME_LEN) {
+                       if (total < cur + sizeof(*ref))
+                               break;
+
+                       /* Still try to read out the remaining part */
+                       len = min_t(u32, total - cur - sizeof(*ref),
+                                   BTRFS_NAME_LEN);
+                       error = REF_ERR_NAME_TOO_LONG;
+               } else {
                        len = name_len;
                        error = 0;
-               } else {
-                       len = BTRFS_NAME_LEN;
-                       error = REF_ERR_NAME_TOO_LONG;
                }
+
                read_extent_buffer(eb, namebuf, (unsigned long)(ref + 1), len);
                add_inode_backref(inode_cache, key->objectid, key->offset,
                                  index, namebuf, len, 0, key->type, error);
@@ -4296,12 +4305,16 @@ next:
 
        index = btrfs_inode_ref_index(node, ref);
        name_len = btrfs_inode_ref_name_len(node, ref);
-       if (name_len <= BTRFS_NAME_LEN) {
-               len = name_len;
-       } else {
-               len = BTRFS_NAME_LEN;
+       if (cur + sizeof(*ref) + name_len > total ||
+           name_len > BTRFS_NAME_LEN) {
                warning("root %llu INODE_REF[%llu %llu] name too long",
                        root->objectid, ref_key->objectid, ref_key->offset);
+
+               if (total < cur + sizeof(*ref))
+                       goto out;
+               len = min_t(u32, total - cur - sizeof(*ref), BTRFS_NAME_LEN);
+       } else {
+               len = name_len;
        }
 
        read_extent_buffer(node, namebuf, (unsigned long)(ref + 1), len);
@@ -4334,6 +4347,7 @@ next:
        if (cur < total)
                goto next;
 
+out:
        return err;
 }
 
@@ -4471,16 +4485,22 @@ static int find_inode_ref(struct btrfs_root *root, struct btrfs_key *key,
                if (index != (u64)-1 && index != ref_index)
                        goto next_ref;
 
-               if (ref_namelen <= BTRFS_NAME_LEN) {
-                       len = ref_namelen;
-               } else {
-                       len = BTRFS_NAME_LEN;
+               if (cur + sizeof(*ref) + ref_namelen > total ||
+                   ref_namelen > BTRFS_NAME_LEN) {
                        warning("root %llu INODE %s[%llu %llu] name too long",
                                root->objectid,
                                key->type == BTRFS_INODE_REF_KEY ?
                                        "REF" : "EXTREF",
                                key->objectid, key->offset);
+
+                       if (cur + sizeof(*ref) > total)
+                               break;
+                       len = min_t(u32, total - cur - sizeof(*ref),
+                                   BTRFS_NAME_LEN);
+               } else {
+                       len = ref_namelen;
                }
+
                read_extent_buffer(node, ref_namebuf, (unsigned long)(ref + 1),
                                   len);