CVE-2023-53860 in Linux
要約
〜によって VulDB • 2026年05月30日
Based on the stack trace provided, here is the analysis of where the issue is occurring:
### 1. **The Crash/Issue Location** The actual fault or issue is happening inside: ``` blkdev_direct_IO.part.0+0x84a/0x1810 ``` This is a function in the Linux kernel responsible for handling **Direct I/O** (O_DIRECT) operations on block devices.
### 2. **The Call Path** The sequence of calls leading to the crash is: 1. **User Space**: `__x64_sys_preadv2` (System call `preadv2`) 2. **VFS Layer**: `vfs_readv` → `do_iter_read` → `do_iter_readv_writev` 3. **Block Device Layer**: `blkdev_read_iter` 4. **Direct I/O Path**: `blkdev_direct_IO.part.0` ← **CRASH HERE**
### 3. **Key Observations** - **Operation Type**: This is a **read** operation (`blkdev_read_iter`, `do_iter_read`, `preadv2`). - **I/O Mode**: It is using **Direct I/O** (`blkdev_direct_IO`). This bypasses the page cache and reads/writes directly to/from user-space buffers. - **Error Code**: The `RAX` register shows `ffffffffffda`, which is `-218` in signed 64-bit integer. In Linux error codes, `-218` is `-ECANCELED` (Operation Canceled). However, since this is a stack trace from a crash/oops, it’s more likely that the kernel encountered an unexpected condition (like a NULL pointer dereference, invalid memory access, or assertion failure) *inside* `blkdev_direct_IO`, and the `RAX` value might be from a prior operation or part of the faulting context. **The primary issue is the kernel panic/oops itself, not necessarily a user-space error code.**
### 4. **Likely Causes** Crashes in `blkdev_direct_IO` are often caused by: - **Invalid User-Space Memory**: The user-space buffer passed to `preadv2` is invalid, unmapped, or corrupted. - **Block Device Driver Bug**: The underlying block device driver (e.g., NVMe, SCSI, loop device) has a bug in handling direct I/O requests. - **Filesystem Bug**: If the block device is part of a filesystem (like ext4, xfs, btrfs), the filesystem’s direct I/O implementation might be passing incorrect parameters to the block layer. - **Concurrency/Race Condition**: Direct I/O is sensitive to races with page cache operations or other I/O paths.
### 5. **How to Debug Further** 1. **Check Kernel Logs**: Look for more details in `dmesg` or `/var/log/kern.log` around the time of the crash. It may show a specific error message (e.g., "BUG: unable to handle kernel NULL pointer dereference"). 2. **Identify the Block Device**: Determine which block device was being accessed (e.g., `/dev/sda`, `/dev/nvme0n1`). This can often be found in the kernel logs or by checking which process was performing the I/O. 3. **Reproduce with Debugging**: - Enable kernel debugging options (e.g., `CONFIG_DEBUG_INFO`, `CONFIG_KASAN`). - Use `ftrace` or `perf` to trace the exact path. 4. **Check User-Space Application**: - Verify that the user-space application is correctly handling memory buffers (e.g., using `mlock()` if required for Direct I/O). - Ensure the buffer is properly aligned and accessible.
### Summary The crash is in the **kernel’s block device direct I/O path** (`blkdev_direct_IO`) triggered by a `preadv2` system call. The root cause is likely a bug in the block device driver, filesystem, or an invalid user-space memory buffer.
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