x86/int3: Avoid atomic instrumentation (ef882bfe) · Commits · 戴 / test

Use arch_atomic_*() and __READ_ONCE() to ensure nothing untoward creeps in and ruins things. That is; this is the INT3 text poke handler, strictly limit the code that runs in it, lest it inadvertenly hits yet another INT3. Reported-by:

Thomas Gleixner <tglx@linutronix.de> Signed-off-by:

Peter Zijlstra (Intel) <peterz@infradead.org> Signed-off-by:

Thomas Gleixner <tglx@linutronix.de> Reviewed-by:

Masami Hiramatsu <mhiramat@kernel.org> Reviewed-by:

Alexandre Chartre <alexandre.chartre@oracle.com> Acked-by:

Andy Lutomirski <luto@kernel.org> Link: https://lkml.kernel.org/r/20200505135313.517429268@linutronix.de

arch/x86/kernel/alternative.c

+3 −3

Original line number	Diff line number	Diff line
		@@ -1014,9 +1014,9 @@ static struct bp_patching_desc *bp_desc;
		static __always_inline
		struct bp_patching_desc try_get_desc(struct bp_patching_desc *descp)
		{
		struct bp_patching_desc desc = READ_ONCE(descp); /* rcu_dereference */
		struct bp_patching_desc desc = __READ_ONCE(descp); /* rcu_dereference */

		if (!desc \|\| !atomic_inc_not_zero(&desc->refs))
		if (!desc \|\| !arch_atomic_inc_not_zero(&desc->refs))
		return NULL;

		return desc;
		@@ -1025,7 +1025,7 @@ struct bp_patching_desc try_get_desc(struct bp_patching_desc *descp)
		static __always_inline void put_desc(struct bp_patching_desc *desc)
		{
		smp_mb__before_atomic();
		atomic_dec(&desc->refs);
		arch_atomic_dec(&desc->refs);
		}

		static __always_inline void text_poke_addr(struct text_poke_loc tp)

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