From 0853dc4f2678bbb21ff3d7572b0e9b812985bd65 Mon Sep 17 00:00:00 2001 From: ZhengYuan Huang Date: Mon, 17 Aug 2026 21:20:51 +0800 Subject: [PATCH] btrfs: send: reject extents for non-regular inodes [BUG] A corrupted subvolume tree can leave an EXTENT_DATA item attached to an inode whose mode is not S_IFREG or S_IFLNK. During send, such an item can be treated as file data and crash through a NULL address_space operation: BUG: kernel NULL pointer dereference, address: 0000000000000000 #PF: supervisor instruction fetch in kernel mode #PF: error_code(0x0010) - not-present page Call Trace: read_pages+0x80b/0xb30 mm/readahead.c:173 page_cache_ra_unbounded+0x40d/0x890 mm/readahead.c:302 do_page_cache_ra mm/readahead.c:332 [inline] page_cache_ra_order+0xa16/0xcd0 mm/readahead.c:535 page_cache_sync_ra+0x5ce/0x9d0 mm/readahead.c:626 page_cache_sync_readahead include/linux/pagemap.h:1379 [inline] put_file_data fs/btrfs/send.c:5224 [inline] send_write fs/btrfs/send.c:5291 [inline] send_extent_data+0x16b2/0x29b0 fs/btrfs/send.c:5715 send_write_or_clone fs/btrfs/send.c:6135 [inline] process_extent+0x5d4/0x17b0 fs/btrfs/send.c:6504 changed_extent fs/btrfs/send.c:7079 [inline] changed_cb+0x22f9/0x3cd0 fs/btrfs/send.c:7245 full_send_tree fs/btrfs/send.c:7318 [inline] send_subvol fs/btrfs/send.c:7910 [inline] btrfs_ioctl_send+0x46a9/0x57f0 fs/btrfs/send.c:8248 ... [CAUSE] process_extent() skips extent items for symlinks but assumes every other inode with an extent item is a regular file. For a corrupted non-regular inode, btrfs_iget() does not install the regular file address_space operations. The readahead fallback can then call a NULL read_folio callback before the existing validation in btrfs_get_extent() can run. [FIX] Reject extent items for inode types other than regular files and symlinks at the common send extent-processing boundary. Symlink handling is left unchanged because send emits symlink data from read_symlink(). This covers full, incremental and new-generation sends without adding a check to the regular I/O path. Reviewed-by: Qu Wenruo Signed-off-by: ZhengYuan Huang Reviewed-by: David Sterba Signed-off-by: David Sterba --- fs/btrfs/send.c | 7 +++++++ 1 file changed, 7 insertions(+) diff --git a/fs/btrfs/send.c b/fs/btrfs/send.c index dca3570168c7..f88623bbc491 100644 --- a/fs/btrfs/send.c +++ b/fs/btrfs/send.c @@ -6417,6 +6417,13 @@ static int process_extent(struct send_ctx *sctx, if (S_ISLNK(sctx->cur_inode_mode)) return 0; + if (unlikely(!S_ISREG(sctx->cur_inode_mode))) { + btrfs_crit(sctx->send_root->fs_info, + "send: extent for non-regular inode %llu root %llu mode 0%llo", + key->objectid, btrfs_root_id(sctx->send_root), + sctx->cur_inode_mode & S_IFMT); + return -EUCLEAN; + } if (sctx->parent_root && !sctx->cur_inode_new) { ret = is_extent_unchanged(sctx, path, key);