CVE-2023-53224

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

ext4: Fix function prototype mismatch for ext4_feat_ktype

With clangs kernel control flow integrity (kCFI, CONFIG_CFI_CLANG), indirect call targets are validated against the expected function pointer prototype to make sure the call target is valid to help mitigate ROP attacks. If they are not identical, there is a failure at run time, which manifests as either a kernel panic or thread getting killed.

ext4_feat_ktype was setting the release handler to kfree, which doesnt have a matching function prototype. Add a simple wrapper with the correct prototype.

This was found as a result of Clangs new -Wcast-function-type-strict flag, which is more sensitive than the simpler -Wcast-function-type, which only checks for type width mismatches.

Note that this code is only reached when ext4 is a loadable module and it is being unloaded:

CFI failure at kobject_put+0xbb/0x1b0 (target: kfree+0x0/0x180; expected type: 0x7c4aa698) … RIP: 0010:kobject_put+0xbb/0x1b0 … Call Trace: ext4_exit_sysfs+0x14/0x60 [ext4] cleanup_module+0x67/0xedb [ext4]

Weakness

The product does not sufficiently track and release allocated memory after it has been used, making the memory unavailable for reallocation and reuse.

Affected Software

Potential Mitigations

• Choose a language or tool that provides automatic memory management, or makes manual memory management less error-prone.
• For example, glibc in Linux provides protection against free of invalid pointers.
• When using Xcode to target OS X or iOS, enable automatic reference counting (ARC) [REF-391].
• To help correctly and consistently manage memory when programming in C++, consider using a smart pointer class such as std::auto_ptr (defined by ISO/IEC ISO/IEC 14882:2003), std::shared_ptr and std::unique_ptr (specified by an upcoming revision of the C++ standard, informally referred to as C++ 1x), or equivalent solutions such as Boost.

References

• https://git.kernel.org/stable/c/0a1394e07c5d6bf1bfc25db8589ff1b1bfb6f46a
• https://git.kernel.org/stable/c/118901ad1f25d2334255b3d50512fa20591531cd
• https://git.kernel.org/stable/c/1ba10d3640e9783dad811fe4e24d55465c37c64d
• https://git.kernel.org/stable/c/2b69cdd9f9a7f596e3dd31f05f9852940d177924
• https://git.kernel.org/stable/c/94d8de83286fb1827340eba35b61c308f6b46ead
• https://git.kernel.org/stable/c/99e3fd21f8fc975c95e8cf76fbf6a3d2656f8f71
• https://git.kernel.org/stable/c/c98077f7598a562f51051eec043be0cb3e1b1b5e