From: Zhang Cen Date: Sun, 24 May 2026 11:12:48 +0000 (+0800) Subject: ocfs2: reject oversized group bitmap descriptors X-Git-Url: http://git.ipfire.org/gitweb.cgi?a=commitdiff_plain;h=9bd541e09dffff27e5bec0f9f45b0228173a5375;p=thirdparty%2Flinux.git ocfs2: reject oversized group bitmap descriptors ocfs2_validate_gd_parent() only bounds bg_bits against the parent allocator's chain geometry. A malicious descriptor can still claim a bg_size/bg_bits pair that exceeds the bitmap bytes that physically fit in the group descriptor block, so later bitmap scans and bit updates can run past bg_bitmap. Add a physical-cap check based on ocfs2_group_bitmap_size() for the parent allocator type and reject descriptors whose bg_size or bg_bits exceed that capacity. Keep the existing chain geometry check so both the on-disk bitmap layout and the allocator metadata must agree before the descriptor is used. Validation reproduced this kernel report: KASAN use-after-free in _find_next_bit+0x7f/0xc0 Read of size 8 Call trace: dump_stack_lvl+0x66/0xa0 (?:?) print_report+0xd0/0x630 (?:?) _find_next_bit+0x7f/0xc0 (?:?) srso_alias_return_thunk+0x5/0xfbef5 (?:?) __virt_addr_valid+0x188/0x2f0 (?:?) kasan_report+0xe4/0x120 (?:?) ocfs2_find_max_contig_free_bits+0x35/0x70 (fs/ocfs2/suballoc.c:1375) ocfs2_block_group_set_bits+0x472/0x4b0 (fs/ocfs2/suballoc.c:1457) ocfs2_cluster_group_search+0x16b/0x440 (fs/ocfs2/suballoc.c:86) ocfs2_bg_discontig_fix_result+0x1ef/0x230 (fs/ocfs2/suballoc.c:1786) ocfs2_search_chain+0x8f8/0x10a0 (fs/ocfs2/suballoc.c:1886) get_page_from_freelist+0x70e/0x2370 (?:?) lock_release+0xc6/0x290 (?:?) do_raw_spin_unlock+0x9a/0x100 (?:?) kasan_unpoison+0x27/0x60 (?:?) __bfs+0x147/0x240 (?:?) get_page_from_freelist+0x83d/0x2370 (?:?) ocfs2_claim_suballoc_bits+0x38c/0xe70 (fs/ocfs2/suballoc.c:96) sched_domains_numa_masks_clear+0x70/0xd0 (?:?) check_irq_usage+0xe8/0xb70 (?:?) __ocfs2_claim_clusters+0x18d/0x4c0 (fs/ocfs2/suballoc.c:2497) check_path+0x24/0x50 (?:?) rcu_is_watching+0x20/0x50 (?:?) check_prev_add+0xfd/0xd00 (?:?) ocfs2_add_clusters_in_btree+0x17d/0x810 (fs/ocfs2/suballoc.c:?) __folio_batch_add_and_move+0x1f5/0x3d0 (?:?) ocfs2_add_inode_data+0xd9/0x120 (fs/ocfs2/suballoc.c:?) filemap_add_folio+0x105/0x1f0 (?:?) ocfs2_write_begin_nolock+0x29f7/0x2f80 (fs/ocfs2/suballoc.c:3043) ocfs2_read_inode_block+0xb5/0x110 (fs/ocfs2/suballoc.c:?) down_write+0xf5/0x180 (?:?) ocfs2_write_begin+0x180/0x240 (fs/ocfs2/suballoc.c:?) __mark_inode_dirty+0x758/0x9a0 (?:?) inode_to_bdi+0x41/0x90 (?:?) balance_dirty_pages_ratelimited_flags+0xf8/0x1d0 (?:?) generic_perform_write+0x252/0x440 (?:?) mnt_put_write_access_file+0x16/0x70 (?:?) file_update_time_flags+0xe4/0x200 (?:?) ocfs2_file_write_iter+0x80a/0x1320 (fs/ocfs2/suballoc.c:?) lock_acquire+0x184/0x2f0 (?:?) ksys_write+0xd2/0x170 (?:?) apparmor_file_permission+0xf5/0x310 (?:?) read_zero+0x8d/0x140 (?:?) lock_is_held_type+0x8f/0x100 (?:?) Link: https://lore.kernel.org/20260524111248.1429884-1-rollkingzzc@gmail.com Fixes: ccd979bdbce9 ("[PATCH] OCFS2: The Second Oracle Cluster Filesystem") Assisted-by: Codex:gpt-5.5 Signed-off-by: Zhang Cen Reviewed-by: Joseph Qi Cc: Mark Fasheh Cc: Joel Becker Cc: Junxiao Bi Cc: Changwei Ge Cc: Jun Piao Cc: Heming Zhao Cc: Signed-off-by: Andrew Morton --- diff --git a/fs/ocfs2/suballoc.c b/fs/ocfs2/suballoc.c index d284e0e37252..a4a2b87a45fe 100644 --- a/fs/ocfs2/suballoc.c +++ b/fs/ocfs2/suballoc.c @@ -231,8 +231,16 @@ static int ocfs2_validate_gd_parent(struct super_block *sb, int resize) { unsigned int max_bits; + unsigned int max_bitmap_bits; + unsigned int max_bitmap_size; + int suballocator; struct ocfs2_group_desc *gd = (struct ocfs2_group_desc *)bh->b_data; + suballocator = le64_to_cpu(di->i_blkno) != OCFS2_SB(sb)->bitmap_blkno; + max_bitmap_size = ocfs2_group_bitmap_size(sb, suballocator, + OCFS2_SB(sb)->s_feature_incompat); + max_bitmap_bits = max_bitmap_size * 8; + if (di->i_blkno != gd->bg_parent_dinode) { do_error("Group descriptor #%llu has bad parent pointer (%llu, expected %llu)\n", (unsigned long long)bh->b_blocknr, @@ -240,6 +248,20 @@ static int ocfs2_validate_gd_parent(struct super_block *sb, (unsigned long long)le64_to_cpu(di->i_blkno)); } + if (le16_to_cpu(gd->bg_size) > max_bitmap_size) { + do_error("Group descriptor #%llu has bitmap size %u but physical max of %u\n", + (unsigned long long)bh->b_blocknr, + le16_to_cpu(gd->bg_size), + max_bitmap_size); + } + + if (le16_to_cpu(gd->bg_bits) > max_bitmap_bits) { + do_error("Group descriptor #%llu has bit count %u but physical max of %u\n", + (unsigned long long)bh->b_blocknr, + le16_to_cpu(gd->bg_bits), + max_bitmap_bits); + } + max_bits = le16_to_cpu(di->id2.i_chain.cl_cpg) * le16_to_cpu(di->id2.i_chain.cl_bpc); if (le16_to_cpu(gd->bg_bits) > max_bits) { do_error("Group descriptor #%llu has bit count of %u\n",