Commit 50bf8080 authored by Peter Zijlstra's avatar Peter Zijlstra Committed by Ingo Molnar
Browse files

static_call: Fix the module key fixup 



Provided the target address of a R_X86_64_PC32 relocation is aligned,
the low two bits should be invariant between the relative and absolute
value.

Turns out the address is not aligned and things go sideways, ensure we
transfer the bits in the absolute form when fixing up the key address.

Fixes: 73f44fe1 ("static_call: Allow module use without exposing static_call_key")
Reported-by: default avatarSteven Rostedt <rostedt@goodmis.org>
Signed-off-by: default avatarPeter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: default avatarIngo Molnar <mingo@kernel.org>
Tested-by: default avatarSteven Rostedt (VMware) <rostedt@goodmis.org>
Link: https://lkml.kernel.org/r/20210225220351.GE4746@worktop.programming.kicks-ass.net
parent a38fd874

kernel/static_call.c

+4 −3
Original line number Diff line number Diff line
@@ -349,7 +349,8 @@ static int static_call_add_module(struct module *mod) 
	struct static_call_site *site;



	for (site = start; site != stop; site++) {

		unsigned long addr = (unsigned long)static_call_key(site);

		unsigned long s_key = (long)site->key + (long)&site->key;

		unsigned long addr = s_key & ~STATIC_CALL_SITE_FLAGS;

		unsigned long key;



		/*
@@ -373,8 +374,8 @@ static int static_call_add_module(struct module *mod) 
			return -EINVAL;

		}



		site->key = (key - (long)&site->key) |

			    (site->key & STATIC_CALL_SITE_FLAGS);

		key |= s_key & STATIC_CALL_SITE_FLAGS;

		site->key = key - (long)&site->key;

	}



	return __static_call_init(mod, start, stop);