From ec67e8d61eb40a4e69b16d8931da217352447367 Mon Sep 17 00:00:00 2001 From: Slawomir Stepien Date: Wed, 15 Jul 2026 12:29:34 +0000 Subject: [PATCH] fs/ntfs3: handle partial allocation in attr_data_get_block_locked() When allocating clusters for a sparse or compressed attribute in attr_data_get_block_locked(), the requested virtual cluster number (vcn0) is aligned down to a frame boundary (vcn). The function then attempts to allocate a full frame of clusters. If the disk is nearly full and highly fragmented, attr_allocate_clusters() might only manage to allocate a small fragment and return success with a partial allocation length. If this partial allocation is so small that it does not even reach the originally requested vcn0 (i.e., end <= vcn0), vcn0 remains unallocated (a sparse hole). When the code subsequently calls run_lookup_entry() for vcn0, it finds the original SPARSE_LCN entry, which triggers a WARN_ON(1). Fix this by adding a check to verify if the partial allocation reached vcn0. If it did not (vcn0 >= end), treat this as an -ENOSPC failure and jump to the undo1 label. This safely rolls back the partial allocation, restores the original size, and repacks the runs, leaving the inode in a consistent state before returning the error to the caller. WARNING: fs/ntfs3/attrib.c:1236 at attr_data_get_block_locked+0x1980/0x25d0 fs/ntfs3/attrib.c:1236 RIP: 0010:attr_data_get_block_locked+0x1980/0x25d0 fs/ntfs3/attrib.c:1236 Call Trace: attr_data_get_block+0x1f1/0x2a0 fs/ntfs3/attrib.c:979 ntfs_fallocate+0xd3d/0xf70 fs/ntfs3/file.c:670 vfs_fallocate+0x663/0x7f0 fs/open.c:338 ksys_fallocate fs/open.c:362 [inline] __do_sys_fallocate fs/open.c:367 [inline] __se_sys_fallocate fs/open.c:365 [inline] __x64_sys_fallocate+0xbf/0x110 fs/open.c:365 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline] do_syscall_64+0x174/0x580 arch/x86/entry/syscall_64.c:94 entry_SYSCALL_64_after_hwframe+0x77/0x7f Fixes: 099ef9ab9203 ("fs/ntfs3: implement iomap-based file operations") Assisted-by: Gemini:gemini-3.1-pro-preview Gemini:gemini-3-flash-preview syzbot Reported-by: syzbot+7be6ad5cb228286af3e3@syzkaller.appspotmail.com Closes: https://syzkaller.appspot.com/bug?extid=7be6ad5cb228286af3e3 Link: https://syzkaller.appspot.com/ai_job?id=3c9dee6e-001d-4972-8bf6-f6c960708246 Signed-off-by: Slawomir Stepien Signed-off-by: Konstantin Komarov --- fs/ntfs3/attrib.c | 4 ++++ 1 file changed, 4 insertions(+) diff --git a/fs/ntfs3/attrib.c b/fs/ntfs3/attrib.c index 922134cabb05..a44c387a3085 100644 --- a/fs/ntfs3/attrib.c +++ b/fs/ntfs3/attrib.c @@ -1257,6 +1257,10 @@ int attr_data_get_block_locked(struct ntfs_inode *ni, CLST vcn, CLST clen, total_size = total_size0 + ((u64)*len << cluster_bits); if (vcn != vcn0) { + if (vcn0 >= end) { + err = -ENOSPC; + goto undo1; + } if (!run_lookup_entry(run, vcn0, lcn, len, NULL)) { err = -EINVAL; goto out;