diff options
| author | Jan Kara <jack@suse.cz> | 2022-05-18 11:33:29 +0200 |
|---|---|---|
| committer | Theodore Ts'o <tytso@mit.edu> | 2022-05-24 21:34:13 +0200 |
| commit | 3ba733f879c2a88910744647e41edeefbc0d92b2 (patch) | |
| tree | b23ac2e1ccd5cd223ccc7cd51ae101698624cc2b /fs/ext4/namei.c | |
| parent | ext4: verify dir block before splitting it (diff) | |
| download | linux-3ba733f879c2a88910744647e41edeefbc0d92b2.tar.xz linux-3ba733f879c2a88910744647e41edeefbc0d92b2.zip | |
ext4: avoid cycles in directory h-tree
A maliciously corrupted filesystem can contain cycles in the h-tree
stored inside a directory. That can easily lead to the kernel corrupting
tree nodes that were already verified under its hands while doing a node
split and consequently accessing unallocated memory. Fix the problem by
verifying traversed block numbers are unique.
Cc: stable@vger.kernel.org
Signed-off-by: Jan Kara <jack@suse.cz>
Link: https://lore.kernel.org/r/20220518093332.13986-2-jack@suse.cz
Signed-off-by: Theodore Ts'o <tytso@mit.edu>
Diffstat (limited to 'fs/ext4/namei.c')
| -rw-r--r-- | fs/ext4/namei.c | 22 |
1 files changed, 19 insertions, 3 deletions
diff --git a/fs/ext4/namei.c b/fs/ext4/namei.c index 7286472e9558..47d0ca4c795b 100644 --- a/fs/ext4/namei.c +++ b/fs/ext4/namei.c @@ -777,12 +777,14 @@ static struct dx_frame * dx_probe(struct ext4_filename *fname, struct inode *dir, struct dx_hash_info *hinfo, struct dx_frame *frame_in) { - unsigned count, indirect; + unsigned count, indirect, level, i; struct dx_entry *at, *entries, *p, *q, *m; struct dx_root *root; struct dx_frame *frame = frame_in; struct dx_frame *ret_err = ERR_PTR(ERR_BAD_DX_DIR); u32 hash; + ext4_lblk_t block; + ext4_lblk_t blocks[EXT4_HTREE_LEVEL]; memset(frame_in, 0, EXT4_HTREE_LEVEL * sizeof(frame_in[0])); frame->bh = ext4_read_dirblock(dir, 0, INDEX); @@ -854,6 +856,8 @@ dx_probe(struct ext4_filename *fname, struct inode *dir, } dxtrace(printk("Look up %x", hash)); + level = 0; + blocks[0] = 0; while (1) { count = dx_get_count(entries); if (!count || count > dx_get_limit(entries)) { @@ -882,15 +886,27 @@ dx_probe(struct ext4_filename *fname, struct inode *dir, dx_get_block(at))); frame->entries = entries; frame->at = at; - if (!indirect--) + + block = dx_get_block(at); + for (i = 0; i <= level; i++) { + if (blocks[i] == block) { + ext4_warning_inode(dir, + "dx entry: tree cycle block %u points back to block %u", + blocks[level], block); + goto fail; + } + } + if (++level > indirect) return frame; + blocks[level] = block; frame++; - frame->bh = ext4_read_dirblock(dir, dx_get_block(at), INDEX); + frame->bh = ext4_read_dirblock(dir, block, INDEX); if (IS_ERR(frame->bh)) { ret_err = (struct dx_frame *) frame->bh; frame->bh = NULL; goto fail; } + entries = ((struct dx_node *) frame->bh->b_data)->entries; if (dx_get_limit(entries) != dx_node_limit(dir)) { |