slab: Achieve better kmalloc caches randomization in kvmalloc

As revealed by this writeup[1], due to the fact that __kmalloc_node (now
renamed to __kmalloc_node_noprof) is an exported symbol and will never
get inlined, using it in kvmalloc_node (now is __kvmalloc_node_noprof)
would make the RET_IP inside always point to the same address:

    upper_caller
        kvmalloc
        kvmalloc_node
        kvmalloc_node_noprof
        __kvmalloc_node_noprof	<-- all macros all the way down here
            __kmalloc_node_noprof
                __do_kmalloc_node(.., _RET_IP_)
            ...			<-- _RET_IP_ points to

That literally means all kmalloc invoked via kvmalloc would use the same
seed for cache randomization (CONFIG_RANDOM_KMALLOC_CACHES), which makes
this hardening non-functional.

The root cause of this problem, IMHO, is that using RET_IP only cannot
identify the actual allocation site in case of kmalloc being called
inside non-inlined wrappers or helper functions. And I believe there
could be similar cases in other functions. Nevertheless, I haven't
thought of any good solution for this. So for now let's solve this
specific case first.

For __kvmalloc_node_noprof, replace __kmalloc_node_noprof and call
__do_kmalloc_node directly instead, so that RET_IP can take the return
address of kvmalloc and differentiate each kvmalloc invocation:

    upper_caller
        kvmalloc
        kvmalloc_node
        kvmalloc_node_noprof
        __kvmalloc_node_noprof	<-- all macros all the way down here
            __do_kmalloc_node(.., _RET_IP_)
        ...			<-- _RET_IP_ points to

Thanks to Tamás Koczka for the report and discussion!

Link: https://github.com/google/security-research/blob/908d59b573960dc0b90adda6f16f7017aca08609/pocs/linux/kernelctf/CVE-2024-27397_mitigation/docs/exploit.md?plain=1#L259 [1]
Reported-by: Tamás Koczka <poprdi@google.com>
Signed-off-by: GONG Ruiqi <gongruiqi1@huawei.com>
Reviewed-by: Hyeonggon Yoo <42.hyeyoo@gmail.com>
Tested-by: Hyeonggon Yoo <42.hyeyoo@gmail.com>
Signed-off-by: Vlastimil Babka <vbabka@suse.cz>

0 files changed, 0 insertions, 0 deletions