On 2023/08/14 10:54, Lianbo Jiang wrote:
> Currently, crash-utility still depends on detecting the kernel version,
> or the asm instruction 'bswap' on X86 64/X86 architectures to decide how
> to deal with the freelist ptr obfuscation, when kernel option
> CONFIG_SLAB_FREELIST_HARDENED is enabled.
>
> As you known, the bit diffusion for freelist ptr obfuscation has
> experienced the changes several times on the kernel side, For most
> distributions, usually they might backport these kernel patches from
> upstream, especially for the old kernel, the 'kmem -s|-S' will fail with
> an error "invalid freepointer", which can be observed on ppc64le and
> S390x architectures, etc. That is really not friendly.
>
> Given that, let's fix the above issues this time, and it won't rely
> on the linux version number or asm instruction 'bswap' to decide how to
> dereference the freelist ptr.
>
> Reported-by: Lucas Oakley <soakley@xxxxxxxxxx>
> Signed-off-by: Lianbo Jiang <lijiang@xxxxxxxxxx>
Thank you for the fix.
Maybe we don't have to revert that patch and can use both of the bswap
way and this way, but seems no big benefit with it, so agree to revert it.
Applied.
Thanks!
Kazu
> ---
> memory.c | 9 ++++++---
> 1 file changed, 6 insertions(+), 3 deletions(-)
>
> diff --git a/memory.c b/memory.c
> index 626c6039c6d9..562914ee9230 100644
> --- a/memory.c
> +++ b/memory.c
> @@ -19654,9 +19654,12 @@ freelist_ptr(struct meminfo *si, ulong ptr, ulong ptr_addr)
> if (VALID_MEMBER(kmem_cache_random)) {
> /* CONFIG_SLAB_FREELIST_HARDENED */
>
> - if (THIS_KERNEL_VERSION >= LINUX(5,7,0))
> - ptr_addr = (sizeof(long) == 8) ? bswap_64(ptr_addr)
> - : bswap_32(ptr_addr);
> + ulong addr = (sizeof(long) == 8) ? bswap_64(ptr_addr) : bswap_32(ptr_addr);
> + addr = ptr ^ si->random ^ addr;
> +
> + if (!addr || accessible(addr))
> + return addr;
> +
> return (ptr ^ si->random ^ ptr_addr);
> } else
> return ptr;
--
Crash-utility mailing list
Crash-utility@xxxxxxxxxx
https://listman.redhat.com/mailman/listinfo/crash-utility
Contribution Guidelines: https://github.com/crash-utility/crash/wiki
