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 <[email protected]>
Signed-off-by: GONG Ruiqi <[email protected]>
---
mm/slub.c | 6 +++---
1 file changed, 3 insertions(+), 3 deletions(-)
diff --git a/mm/slub.c b/mm/slub.c
index abc982d68feb..1f7d1d260eeb 100644
--- a/mm/slub.c
+++ b/mm/slub.c
@@ -4925,9 +4925,9 @@ void *__kvmalloc_node_noprof(DECL_BUCKET_PARAMS(size, b),
gfp_t flags, int node)
* It doesn't really make sense to fallback to vmalloc for sub page
* requests
*/
- ret = __kmalloc_node_noprof(PASS_BUCKET_PARAMS(size, b),
- kmalloc_gfp_adjust(flags, size),
- node);
+ ret = __do_kmalloc_node(size, PASS_BUCKET_PARAM(b),
+ kmalloc_gfp_adjust(flags, size),
+ node, _RET_IP_);
if (ret || size <= PAGE_SIZE)
return ret;
--
2.25.1
