From e706b89c6a83a52f077e7683e602d992309a5751 Mon Sep 17 00:00:00 2001 From: Joseph Qi Date: Tue, 1 Sep 2026 20:52:19 +0800 Subject: [PATCH] ocfs2: validate suballoc bit during inode read i_suballoc_bit of a dinode is currently not validated at all. A corrupted dinode can carry an abnormally large i_suballoc_bit, which bypasses ocfs2_validate_inode_block(). When the inode is deleted, ocfs2_remove_inode() calls ocfs2_free_dinode(), which passes the unvalidated bit to _ocfs2_free_suballoc_bits() and triggers BUG_ON((count + start_bit) > ocfs2_bits_per_group(cl)). A suballocator block group bitmap is contained in a single block and starts after the group descriptor header, so a valid suballoc bit must be smaller than the number of bits fitting in the remaining space. Reject oversized i_suballoc_bit values during dinode validation. The bound is derived from ocfs2_group_bitmap_size() so it is also tight when discontig_bg caps the suballocator bitmap at OCFS2_MAX_BG_BITMAP_SIZE. Note the above check alone is not sufficient since the freeing path compares the bit against ocfs2_bits_per_group(), which is derived from cl_cpg/cl_bpc of the allocator dinode that is not validated against the actual group capacity and can be artificially smaller on a corrupted image. Convert this BUG_ON in _ocfs2_free_suballoc_bits() to ocfs2_error() as well. Link: https://lore.kernel.org/20260901125221.1634686-3-joseph.qi@linux.alibaba.com Signed-off-by: Joseph Qi Signed-off-by: Andrew Morton Cc: Changwei Ge Cc: Heming Zhao Cc: Joel Becker Cc: Jun Piao Cc: Junxiao Bi Cc: Mark Fasheh --- fs/ocfs2/inode.c | 16 ++++++++++++++++ fs/ocfs2/ocfs2.h | 12 ++++++++++++ fs/ocfs2/suballoc.c | 18 +++++++++++++++--- 3 files changed, 43 insertions(+), 3 deletions(-) diff --git a/fs/ocfs2/inode.c b/fs/ocfs2/inode.c index 9228d6ef23c2..92f3450010fb 100644 --- a/fs/ocfs2/inode.c +++ b/fs/ocfs2/inode.c @@ -1547,6 +1547,22 @@ int ocfs2_validate_inode_block(struct super_block *sb, goto bail; } + /* + * A suballocator block group bitmap is contained in a single block + * and starts after the group descriptor header, so a valid suballoc + * bit can never exceed ocfs2_suballoc_bits_per_block(). Otherwise + * deleting the inode will pass the oversized bit to + * _ocfs2_free_suballoc_bits() via ocfs2_free_dinode() and trigger + * BUG_ON((count + start_bit) > ocfs2_bits_per_group(cl)), since any + * group holds at most ocfs2_suballoc_bits_per_block() bits. + */ + if (le16_to_cpu(di->i_suballoc_bit) >= ocfs2_suballoc_bits_per_block(sb)) { + rc = ocfs2_error(sb, "Invalid dinode %llu: suballoc bit %u\n", + (unsigned long long)bh->b_blocknr, + le16_to_cpu(di->i_suballoc_bit)); + goto bail; + } + if ((le32_to_cpu(di->i_flags) & OCFS2_ORPHANED_FL) && le16_to_cpu(di->i_orphaned_slot) >= OCFS2_SB(sb)->max_slots) { rc = ocfs2_error(sb, "Invalid dinode %llu: orphaned slot %u\n", diff --git a/fs/ocfs2/ocfs2.h b/fs/ocfs2/ocfs2.h index b747cdec1787..e3bb3cc0b25a 100644 --- a/fs/ocfs2/ocfs2.h +++ b/fs/ocfs2/ocfs2.h @@ -593,6 +593,18 @@ static inline int ocfs2_supports_discontig_bg(struct ocfs2_super *osb) return 0; } +/* + * A suballocator block group bitmap starts right after the group + * descriptor header, so a suballoc bit can never exceed this number + * of bits. Derive it from ocfs2_group_bitmap_size() which also caps + * it at OCFS2_MAX_BG_BITMAP_SIZE when discontig_bg is enabled. + */ +static inline u32 ocfs2_suballoc_bits_per_block(struct super_block *sb) +{ + return ocfs2_group_bitmap_size(sb, 1, + OCFS2_SB(sb)->s_feature_incompat) * 8; +} + static inline unsigned int ocfs2_link_max(struct ocfs2_super *osb) { if (ocfs2_supports_indexed_dirs(osb)) diff --git a/fs/ocfs2/suballoc.c b/fs/ocfs2/suballoc.c index 453b56be9624..ce22d0c3d287 100644 --- a/fs/ocfs2/suballoc.c +++ b/fs/ocfs2/suballoc.c @@ -3040,10 +3040,22 @@ static int _ocfs2_free_suballoc_bits(handle_t *handle, /* The alloc_bh comes from ocfs2_free_dinode() or * ocfs2_free_clusters(). The callers have all locked the * allocator and gotten alloc_bh from the lock call. This - * validates the dinode buffer. Any corruption that has happened - * is a code bug. */ + * validates the dinode buffer. */ BUG_ON(!OCFS2_IS_VALID_DINODE(fe)); - BUG_ON((count + start_bit) > ocfs2_bits_per_group(cl)); + + /* + * ocfs2_bits_per_group() is derived from cl_cpg and cl_bpc of the + * allocator dinode, which are not validated against the volume + * geometry. A corrupted image can carry a suballoc bit beyond it, + * so error out instead of crashing. + */ + if ((count + start_bit) > ocfs2_bits_per_group(cl)) { + return ocfs2_error(alloc_inode->i_sb, + "Allocator #%llu: freeing bits %u+%u exceeds bits per group %u\n", + (unsigned long long)le64_to_cpu(fe->i_blkno), + count, start_bit, + ocfs2_bits_per_group(cl)); + } trace_ocfs2_free_suballoc_bits( (unsigned long long)OCFS2_I(alloc_inode)->ip_blkno,