CVE-2022-50737 in Linux
सारांश
द्वारा VulDB • 13/05/2026
Based on the kernel log snippet provided, here is an analysis of the crash and the likely cause.
### **Summary** This is a **KASAN (Kernel Address Sanitizer)** report indicating a **use-after-free** or **invalid memory access** in the `__x64_sys_mount` system call. The crash occurred while accessing a memory address that belongs to a **freed physical page** (`refcount:0`, `mapcount:0`).
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### **Detailed Analysis**
#### **1. The Crash Location** - **Function:** `__x64_sys_mount+0xca/0x110` - This indicates the crash happened inside the `mount` system call implementation in the kernel. - **RIP:** `0x7f9d374e948a` - This is a user-space address (starts with `0x7f...`), which is unusual for a kernel crash unless: - The kernel was executing code that was mapped into user space (e.g., via `mmap` or `vDSO`), **OR** - The RIP shown is from the user-space stack trace, and the actual kernel crash happened earlier in the call chain. However, the presence of `__kasan_check_write` suggests the kernel itself detected the invalid access.
#### **2. The Buggy Address** - **Message:** `The buggy address belongs to the physical page:` - **Page Info:** ``` page:000000003e38a3d5 refcount:0 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x37bc flags: 0xfffffc0000000(node=0|zone=1|lastcpupid=0x1fffff) ``` - **`refcount:0`**: The page has no references. It is **freed**. - **`mapcount:0`**: The page is not mapped into any process's page tables. - **`mapping:0000000000000000`**: No address space mapping. - **Conclusion:** The kernel tried to write to (`__kasan_check_write`) a memory address that was already freed and returned to the buddy allocator. This is a classic **Use-After-Free (UAF)** bug.
#### **3. KASAN Context** - `__kasan_check_write+0x14/0x20`: KASAN intercepts memory accesses to detect invalid reads/writes. The fact that it triggered means the access was to a poisoned (freed) memory region.
#### **4. System Call Context** - **SYSCALL:** `mount` (syscall number `0xa5` = 165 in decimal, as seen in `ORIG_RAX: 00000000000000a5`). - **User-space arguments:** - `RDI`: `0000561cdb442af0` (likely `mountpoint` path) - `RSI`: `0000561cdb43a2e0` (likely `source` path) - `RDX`: `0000561cdb43a260` (likely `type` string) - `R10`: `00000000c0ed0000` (likely `flags`)
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### **Likely Causes**
1. **Use-After-Free in Mount Path Resolution:** - The `mount` syscall involves resolving paths, checking permissions, and interacting with filesystem drivers. - A driver or VFS layer code may have freed a buffer (e.g., a path string, inode, or superblock structure) but still held a pointer to it, which was then accessed during the mount operation.
2. **Race Condition:** - If the mount is being performed concurrently with another operation that frees resources (e.g., unmounting, module removal, or filesystem cleanup), a race condition could lead to accessing freed memory.
3. **Corrupted Pointer:** - A pointer in the kernel stack or heap may have been corrupted, pointing to a freed page.
4. **Driver Bug:** - If a specific filesystem (e.g., NFS, CIFS, FUSE, or a custom driver) is being mounted, the bug is likely in that driver's code.
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### **How to Debug Further**
1. **Check Full KASAN Report:** - The
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