Re: [PATCH 1/3] livepatch: Fail object initialization on duplicate patched function

[Petr Mladek <pmladek@suse.com>]

On Mon 2026-08-31 01:33:06, Harry Hsu wrote:
> Several symbols can share one address:
> 
>   ffffffff8ed7fef0 t __do_sys_fork
>   ffffffff8ed7fef0 T __ia32_sys_fork
>   ffffffff8ed7fef0 T __x64_sys_fork
> 
> klp_find_ops() looks the ops up by func->old_func, i.e. by address, so
> two klp_funcs of the same livepatch naming two of these symbols resolve
> to the same klp_ops and are both pushed onto one ops->func_stack.
> 
> This breaks the assumption that a single livepatch contributes at most
> one entry to any func_stack.  klp_ftrace_handler() picks the entry at
> the top of the stack, but when both entries belong to the same livepatch
> there is nothing that says which of them should be used in the PATCHED
> state, and the UNPATCHED state has to end up at the original function
> either way.  klp_check_stack_func() cannot tell them apart either: it
> asks whether the preceding entry is the original function or another
> livepatch's replacement, and an aliased sibling is neither.
> 
> Patching two aliases of one function from a single livepatch was never
> meaningful, so fail object initialization in klp_init_object_loaded()
> rather than leave the redirection undefined.
> 
> Fixes: 3c33f5b99d68 ("livepatch: support for repatching a function")
> Suggested-by: Petr Mladek <pmladek@suse.com>
> Signed-off-by: Harry Hsu <x90613@gmail.com>

Looks good to me and passes selftests:

Reviewed-by: Petr Mladek <pmladek@suse.com>
Tested-by: Petr Mladek <pmladek@suse.com>

Best Regards,
Petr