printk: ringbuffer: avoid memcpy() on state_var (e7c1fe21) · Commits · 戴 / test

@state_var is copied as part of the descriptor copying via memcpy(). This is not allowed because @state_var is an atomic type, which in some implementations may contain a spinlock. Avoid using memcpy() with @state_var by explicitly copying the other fields of the descriptor. @state_var is set using atomic set operator before returning. Fixes: ("printk: add lockless ringbuffer") Signed-off-by:

John Ogness <john.ogness@linutronix.de> Reviewed-by:

Petr Mladek <pmladek@suse.com> Signed-off-by:

Petr Mladek <pmladek@suse.com> Link: https://lore.kernel.org/r/20200914094803.27365-2-john.ogness@linutronix.de

kernel/printk/printk_ringbuffer.c

+7 −2

Original line number	Diff line number	Diff line
		@@ -412,9 +412,14 @@ static enum desc_state desc_read(struct prb_desc_ring *desc_ring,

		/*
		* Copy the descriptor data. The data is not valid until the
		* state has been re-checked.
		*/
		memcpy(desc_out, desc, sizeof(desc_out)); / LMM(desc_read:C) */
		* state has been re-checked. A memcpy() for all of @desc
		* cannot be used because of the atomic_t @state_var field.
		*/
		memcpy(&desc_out->info, &desc->info, sizeof(desc_out->info)); /* LMM(desc_read:C) */
		memcpy(&desc_out->text_blk_lpos, &desc->text_blk_lpos,
		sizeof(desc_out->text_blk_lpos)); /* also part of desc_read:C */
		memcpy(&desc_out->dict_blk_lpos, &desc->dict_blk_lpos,
		sizeof(desc_out->dict_blk_lpos)); /* also part of desc_read:C */

		/*
		* 1. Guarantee the descriptor content is loaded before re-checking

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