In the Linux kernel, the following vulnerability has been resolved:

ext4: silence the warning when evicting inode with dioread_nolock

When evicting an inode with default dioread_nolock, it could be raced by the unwritten extents converting kworker after writeback some new allocated dirty blocks. It convert unwritten extents to written, the extents could be merged to upper level and free extent blocks, so it could mark the inode dirty again even this inode has been marked I_FREEING. But the inode->i_io_list check and warning in ext4_evict_inode() missing this corner case. Fortunately, ext4_evict_inode() will wait all extents converting finished before this check, so it will not lead to inode use-after-free problem, every thing is OK besides this warning. The WARN_ON_ONCE was originally designed for finding inode use-after-free issues in advance, but if we add current dioread_nolock case in, it will become not quite useful, so fix this warning by just remove this check.

====== WARNING: CPU: 7 PID: 1092 at fs/ext4/inode.c:227 ext4_evict_inode+0x875/0xc60 … RIP: 0010:ext4_evict_inode+0x875/0xc60 … Call Trace: evict+0x11c/0x2b0 iput+0x236/0x3a0 do_unlinkat+0x1b4/0x490 __x64_sys_unlinkat+0x4c/0xb0 do_syscall_64+0x3b/0x90 entry_SYSCALL_64_after_hwframe+0x46/0xb0 RIP: 0033:0x7fa933c1115b

rm kworker ext4_end_io_end() vfs_unlink() ext4_unlink() ext4_convert_unwritten_io_end_vec() ext4_convert_unwritten_extents() ext4_map_blocks() ext4_ext_map_blocks() ext4_ext_try_to_merge_up() __mark_inode_dirty() check !I_FREEING locked_inode_to_wb_and_lock_list() iput() iput_final() evict() ext4_evict_inode() truncate_inode_pages_final() //wait release io_end inode_io_list_move_locked() ext4_release_io_end() trigger WARN_ON_ONCE()

Affected Software

References

• https://git.kernel.org/stable/c/0d041b7251c13679a0f6c7926751ce1d8a7237c1
• https://git.kernel.org/stable/c/3b893cc9a8d8b4e486a6639f5e107b56b7197d2e
• https://git.kernel.org/stable/c/b085fb43feede48ebf80ab7e2dd150c8d9902932
• https://git.kernel.org/stable/c/bc12ac98ea2e1b70adc6478c8b473a0003b659d3
• https://git.kernel.org/stable/c/bdc698ce91f232fd5eb11d2373e9f82f687314b8