mm/slub: avoid accessing metadata when pointer is invalid in object_err()

Vulnerability Description

In the Linux kernel, the following vulnerability has been resolved: mm/slub: avoid accessing metadata when pointer is invalid in object_err() object_err() reports details of an object for further debugging, such as the freelist pointer, redzone, etc. However, if the pointer is invalid, attempting to access object metadata can lead to a crash since it does not point to a valid object. One known path to the crash is when alloc_consistency_checks() determines the pointer to the allocated object is invalid because of a freelist corruption, and calls object_err() to report it. The debug code should report and handle the corruption gracefully and not crash in the process. In case the pointer is NULL or check_valid_pointer() returns false for the pointer, only print the pointer value and skip accessing metadata.

References

• https://git.kernel.org/stable/c/872f2c34ff232af1e65ad2df86d61163c8ffad42
• https://git.kernel.org/stable/c/f66012909e7bf383fcdc5850709ed5716073fdc4
• https://git.kernel.org/stable/c/7e287256904ee796c9477e3ec92b07f236481ef3
• https://git.kernel.org/stable/c/1f0797f17927b5cad0fb7eced422f9a7c30a3191
• https://git.kernel.org/stable/c/0ef7058b4dc6fcef622ac23b45225db57f17b83f
• https://git.kernel.org/stable/c/dda6ec365ab04067adae40ef17015db447e90736
• https://git.kernel.org/stable/c/3baa1da473e6e50281324ff1d332d1a07a3bb02e
• https://git.kernel.org/stable/c/b4efccec8d06ceb10a7d34d7b1c449c569d53770