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If anyone has any objections, please let me know. ------------------ From: Edward Adam Davis [ Upstream commit e0b0f2834c9bec51b1068de5cf5e10c7519143eb ] syzbot constructed a corrupted image, which resulted in el->l_count from the b-tree extent block being 0. Since the length of the l_recs array depends on l_count, reading its member e_blkno triggered the out-of-bounds access reported by syzbot in [1]. The loop terminates when l_count is 0, similar to when next_free is 0. [1] UBSAN: array-index-out-of-bounds in fs/ocfs2/alloc.c:1838:11 index 0 is out of range for type 'struct ocfs2_extent_rec[] __counted_by(l_count)' (aka 'struct ocfs2_extent_rec[]') Call Trace: __ocfs2_find_path+0x606/0xa40 fs/ocfs2/alloc.c:1838 ocfs2_find_leaf+0xab/0x1c0 fs/ocfs2/alloc.c:1946 ocfs2_get_clusters_nocache+0x172/0xc60 fs/ocfs2/extent_map.c:418 ocfs2_get_clusters+0x505/0xa70 fs/ocfs2/extent_map.c:631 ocfs2_extent_map_get_blocks+0x202/0x6a0 fs/ocfs2/extent_map.c:678 ocfs2_read_virt_blocks+0x286/0x930 fs/ocfs2/extent_map.c:1001 ocfs2_read_dir_block fs/ocfs2/dir.c:521 [inline] ocfs2_find_entry_el fs/ocfs2/dir.c:728 [inline] ocfs2_find_entry+0x3e4/0x2090 fs/ocfs2/dir.c:1120 ocfs2_find_files_on_disk+0xdf/0x310 fs/ocfs2/dir.c:2023 ocfs2_lookup_ino_from_name+0x52/0x100 fs/ocfs2/dir.c:2045 _ocfs2_get_system_file_inode fs/ocfs2/sysfile.c:136 [inline] ocfs2_get_system_file_inode+0x326/0x770 fs/ocfs2/sysfile.c:112 ocfs2_init_global_system_inodes+0x319/0x660 fs/ocfs2/super.c:461 ocfs2_initialize_super fs/ocfs2/super.c:2196 [inline] ocfs2_fill_super+0x4432/0x65b0 fs/ocfs2/super.c:993 get_tree_bdev_flags+0x40e/0x4d0 fs/super.c:1691 vfs_get_tree+0x92/0x2a0 fs/super.c:1751 fc_mount fs/namespace.c:1199 [inline] Link: https://lkml.kernel.org/r/tencent_4D99464FA28D9225BE0DBA923F5DF6DD8C07@qq.com Signed-off-by: Edward Adam Davis Reported-by: syzbot+151afab124dfbc5f15e6@syzkaller.appspotmail.com Closes: https://syzkaller.appspot.com/bug?extid=151afab124dfbc5f15e6 Reviewed-by: Heming Zhao Acked-by: Joseph Qi Cc: Mark Fasheh Cc: Joel Becker Cc: Junxiao Bi Cc: Changwei Ge Cc: Jun Piao Signed-off-by: Andrew Morton Stable-dep-of: 6193ce7896af ("ocfs2: fix array out of bound access in __ocfs2_find_path()") Signed-off-by: Sasha Levin --- fs/ocfs2/alloc.c | 9 +++++---- 1 file changed, 5 insertions(+), 4 deletions(-) diff --git a/fs/ocfs2/alloc.c b/fs/ocfs2/alloc.c index d22ad99c9ebee..58f92a02ed68a 100644 --- a/fs/ocfs2/alloc.c +++ b/fs/ocfs2/alloc.c @@ -1811,14 +1811,15 @@ static int __ocfs2_find_path(struct ocfs2_caching_info *ci, ret = -EROFS; goto out; } - if (le16_to_cpu(el->l_next_free_rec) == 0) { + if (!el->l_next_free_rec || !el->l_count) { ocfs2_error(ocfs2_metadata_cache_get_super(ci), - "Owner %llu has empty extent list at depth %u\n", + "Owner %llu has empty extent list at depth %u\n" + "(next free=%u count=%u)\n", (unsigned long long)ocfs2_metadata_cache_owner(ci), - le16_to_cpu(el->l_tree_depth)); + le16_to_cpu(el->l_tree_depth), + le16_to_cpu(el->l_next_free_rec), le16_to_cpu(el->l_count)); ret = -EROFS; goto out; - } for(i = 0; i < le16_to_cpu(el->l_next_free_rec) - 1; i++) { -- 2.53.0